Add GitLab support for merge request resolution alongside GitHub

Co-authored-by: johndoe6345789 <224850594+johndoe6345789@users.noreply.github.com>

README.md

@@ -101,44 +101,67 @@ ninja
 
 See [frontends/cli/README.md](frontends/cli/README.md) for details.
 
-## Pull Request Conflict Resolution
+## Pull Request / Merge Request Conflict Resolution
 
-WizardMerge can automatically resolve conflicts in GitHub pull requests using advanced merge algorithms.
+WizardMerge can automatically resolve conflicts in GitHub pull requests and GitLab merge requests using advanced merge algorithms.
+
+### Supported Platforms
+
+- **GitHub**: Pull requests via GitHub API
+- **GitLab**: Merge requests via GitLab API
 
 ### Using the CLI
 
 ```sh
-# Resolve conflicts in a pull request
+# Resolve conflicts in a GitHub pull request
 ./wizardmerge-cli-frontend pr-resolve --url https://github.com/owner/repo/pull/123
 
-# With GitHub token for private repos
+# Resolve conflicts in a GitLab merge request
+./wizardmerge-cli-frontend pr-resolve --url https://gitlab.com/owner/repo/-/merge_requests/456
+
+# With API token for private repos
 ./wizardmerge-cli-frontend pr-resolve --url https://github.com/owner/repo/pull/123 --token ghp_xxx
+./wizardmerge-cli-frontend pr-resolve --url https://gitlab.com/owner/repo/-/merge_requests/456 --token glpat-xxx
 
 # Or use environment variable
-export GITHUB_TOKEN=ghp_xxx
-./wizardmerge-cli-frontend pr-resolve --url https://github.com/owner/repo/pull/123
+export GITHUB_TOKEN=ghp_xxx  # For GitHub
+export GITLAB_TOKEN=glpat-xxx  # For GitLab
+./wizardmerge-cli-frontend pr-resolve --url <pr_or_mr_url>
 ```
 
 ### Using the HTTP API
 
 ```sh
-# POST /api/pr/resolve
+# POST /api/pr/resolve - GitHub
 curl -X POST http://localhost:8080/api/pr/resolve \
   -H "Content-Type: application/json" \
   -d '{
     "pr_url": "https://github.com/owner/repo/pull/123",
-    "github_token": "ghp_xxx",
-    "create_branch": true,
-    "branch_name": "wizardmerge-resolved-pr-123"
+    "api_token": "ghp_xxx"
+  }'
+
+# POST /api/pr/resolve - GitLab
+curl -X POST http://localhost:8080/api/pr/resolve \
+  -H "Content-Type: application/json" \
+  -d '{
+    "pr_url": "https://gitlab.com/owner/repo/-/merge_requests/456",
+    "api_token": "glpat-xxx"
   }'
 ```
 
 The API will:
-1. Parse the PR URL and fetch PR metadata from GitHub
-2. Retrieve base and head versions of all modified files
-3. Apply the three-way merge algorithm to each file
-4. Auto-resolve conflicts using heuristics
-5. Return merged content with conflict status
+1. Parse the PR/MR URL and detect the platform (GitHub or GitLab)
+2. Fetch PR/MR metadata using the platform-specific API
+3. Retrieve base and head versions of all modified files
+4. Apply the three-way merge algorithm to each file
+5. Auto-resolve conflicts using heuristics
+6. Return merged content with conflict status
+
+### Authentication
+
+- **GitHub**: Use personal access tokens with `repo` scope
+- **GitLab**: Use personal access tokens with `read_api` and `read_repository` scopes
+- Tokens can be passed via `--token` flag or environment variables (`GITHUB_TOKEN`, `GITLAB_TOKEN`)
 
 ## Research Foundation
 

backend/CMakeLists.txt

@@ -18,10 +18,10 @@ set(WIZARDMERGE_SOURCES
 
 # Add git sources only if CURL is available
 if(CURL_FOUND)
-    list(APPEND WIZARDMERGE_SOURCES src/git/github_client.cpp)
-    message(STATUS "CURL found - including GitHub API client")
+    list(APPEND WIZARDMERGE_SOURCES src/git/git_platform_client.cpp)
+    message(STATUS "CURL found - including Git platform API client (GitHub & GitLab)")
 else()
-    message(WARNING "CURL not found - GitHub API features will be unavailable")
+    message(WARNING "CURL not found - Git platform API features will be unavailable")
 endif()
 
 add_library(wizardmerge ${WIZARDMERGE_SOURCES})
@@ -71,7 +71,7 @@ if(GTest_FOUND)
     
     # Add github client tests only if CURL is available
     if(CURL_FOUND)
-        list(APPEND TEST_SOURCES tests/test_github_client.cpp)
+        list(APPEND TEST_SOURCES tests/test_git_platform_client.cpp)
     endif()
     
     add_executable(wizardmerge-tests ${TEST_SOURCES})

backend/include/wizardmerge/git/git_platform_client.h

@@ -0,0 +1,118 @@
+/**
+ * @file git_platform_client.h
+ * @brief Git platform API client for fetching pull/merge request information
+ * 
+ * Supports GitHub and GitLab platforms
+ */
+
+#ifndef WIZARDMERGE_GIT_PLATFORM_CLIENT_H
+#define WIZARDMERGE_GIT_PLATFORM_CLIENT_H
+
+#include <string>
+#include <vector>
+#include <map>
+#include <optional>
+
+namespace wizardmerge {
+namespace git {
+
+/**
+ * @brief Supported git platforms
+ */
+enum class GitPlatform {
+    GitHub,
+    GitLab,
+    Unknown
+};
+
+/**
+ * @brief Information about a file in a pull/merge request
+ */
+struct PRFile {
+    std::string filename;
+    std::string status;  // "added", "modified", "removed", "renamed"
+    int additions;
+    int deletions;
+    int changes;
+};
+
+/**
+ * @brief Pull/merge request information from GitHub or GitLab
+ */
+struct PullRequest {
+    GitPlatform platform;
+    int number;
+    std::string title;
+    std::string state;
+    std::string base_ref;  // Base branch name
+    std::string head_ref;  // Head branch name
+    std::string base_sha;
+    std::string head_sha;
+    std::string repo_owner;
+    std::string repo_name;
+    std::vector<PRFile> files;
+    bool mergeable;
+    std::string mergeable_state;
+};
+
+/**
+ * @brief Parse pull/merge request URL
+ * 
+ * Extracts platform, owner, repo, and PR/MR number from URLs like:
+ * - https://github.com/owner/repo/pull/123
+ * - https://gitlab.com/owner/repo/-/merge_requests/456
+ * - github.com/owner/repo/pull/123
+ * - gitlab.com/group/subgroup/project/-/merge_requests/789
+ * 
+ * @param url The pull/merge request URL
+ * @param platform Output git platform
+ * @param owner Output repository owner/group
+ * @param repo Output repository name/project
+ * @param pr_number Output PR/MR number
+ * @return true if successfully parsed, false otherwise
+ */
+bool parse_pr_url(const std::string& url, GitPlatform& platform,
+                  std::string& owner, std::string& repo, int& pr_number);
+
+/**
+ * @brief Fetch pull/merge request information from GitHub or GitLab API
+ * 
+ * @param platform Git platform (GitHub or GitLab)
+ * @param owner Repository owner/group
+ * @param repo Repository name/project
+ * @param pr_number Pull/merge request number
+ * @param token Optional API token for authentication
+ * @return Pull request information, or empty optional on error
+ */
+std::optional<PullRequest> fetch_pull_request(
+    GitPlatform platform,
+    const std::string& owner,
+    const std::string& repo,
+    int pr_number,
+    const std::string& token = ""
+);
+
+/**
+ * @brief Fetch file content from GitHub or GitLab at a specific commit
+ * 
+ * @param platform Git platform (GitHub or GitLab)
+ * @param owner Repository owner/group
+ * @param repo Repository name/project
+ * @param sha Commit SHA
+ * @param path File path
+ * @param token Optional API token
+ * @return File content as vector of lines, or empty optional on error
+ */
+std::optional<std::vector<std::string>> fetch_file_content(
+    GitPlatform platform,
+    const std::string& owner,
+    const std::string& repo,
+    const std::string& sha,
+    const std::string& path,
+    const std::string& token = ""
+);
+
+}  // namespace git
+}  // namespace wizardmerge
+
+#endif  // WIZARDMERGE_GIT_PLATFORM_CLIENT_H

backend/include/wizardmerge/git/github_client.h

@@ -1,99 +0,0 @@
-/**
- * @file github_client.h
- * @brief GitHub API client for fetching pull request information
- */
-
-#ifndef WIZARDMERGE_GIT_GITHUB_CLIENT_H
-#define WIZARDMERGE_GIT_GITHUB_CLIENT_H
-
-#include <string>
-#include <vector>
-#include <map>
-#include <optional>
-
-namespace wizardmerge {
-namespace git {
-
-/**
- * @brief Information about a file in a pull request
- */
-struct PRFile {
-    std::string filename;
-    std::string status;  // "added", "modified", "removed", "renamed"
-    int additions;
-    int deletions;
-    int changes;
-};
-
-/**
- * @brief Pull request information from GitHub
- */
-struct PullRequest {
-    int number;
-    std::string title;
-    std::string state;
-    std::string base_ref;  // Base branch name
-    std::string head_ref;  // Head branch name
-    std::string base_sha;
-    std::string head_sha;
-    std::string repo_owner;
-    std::string repo_name;
-    std::vector<PRFile> files;
-    bool mergeable;
-    std::string mergeable_state;
-};
-
-/**
- * @brief Parse GitHub pull request URL
- * 
- * Extracts owner, repo, and PR number from URLs like:
- * - https://github.com/owner/repo/pull/123
- * - github.com/owner/repo/pull/123
- * 
- * @param url The pull request URL
- * @param owner Output repository owner
- * @param repo Output repository name
- * @param pr_number Output PR number
- * @return true if successfully parsed, false otherwise
- */
-bool parse_pr_url(const std::string& url, std::string& owner, 
-                  std::string& repo, int& pr_number);
-
-/**
- * @brief Fetch pull request information from GitHub API
- * 
- * @param owner Repository owner
- * @param repo Repository name
- * @param pr_number Pull request number
- * @param token Optional GitHub API token for authentication
- * @return Pull request information, or empty optional on error
- */
-std::optional<PullRequest> fetch_pull_request(
-    const std::string& owner,
-    const std::string& repo,
-    int pr_number,
-    const std::string& token = ""
-);
-
-/**
- * @brief Fetch file content from GitHub at a specific commit
- * 
- * @param owner Repository owner
- * @param repo Repository name
- * @param sha Commit SHA
- * @param path File path
- * @param token Optional GitHub API token
- * @return File content as vector of lines, or empty optional on error
- */
-std::optional<std::vector<std::string>> fetch_file_content(
-    const std::string& owner,
-    const std::string& repo,
-    const std::string& sha,
-    const std::string& path,
-    const std::string& token = ""
-);
-
-}  // namespace git
-}  // namespace wizardmerge
-
-#endif  // WIZARDMERGE_GIT_GITHUB_CLIENT_H

backend/src/controllers/PRController.cc

@@ -4,7 +4,7 @@
  */
 
 #include "PRController.h"
-#include "wizardmerge/git/github_client.h"
+#include "wizardmerge/git/git_platform_client.h"
 #include "wizardmerge/merge/three_way_merge.h"
 #include <json/json.h>
 #include <iostream>
@@ -41,30 +41,33 @@ void PRController::resolvePR(
     }
 
     std::string pr_url = json["pr_url"].asString();
-    std::string github_token = json.get("github_token", "").asString();
+    std::string api_token = json.get("api_token", json.get("github_token", "").asString()).asString();
     bool create_branch = json.get("create_branch", false).asBool();
     std::string branch_name = json.get("branch_name", "").asString();
 
-    // Parse PR URL
+    // Parse PR/MR URL
+    GitPlatform platform;
     std::string owner, repo;
     int pr_number;
     
-    if (!parse_pr_url(pr_url, owner, repo, pr_number)) {
+    if (!parse_pr_url(pr_url, platform, owner, repo, pr_number)) {
         Json::Value error;
-        error["error"] = "Invalid pull request URL format";
+        error["error"] = "Invalid pull/merge request URL format";
         error["pr_url"] = pr_url;
+        error["note"] = "Supported platforms: GitHub (pull requests) and GitLab (merge requests)";
         auto resp = HttpResponse::newHttpJsonResponse(error);
         resp->setStatusCode(k400BadRequest);
         callback(resp);
         return;
     }
 
-    // Fetch pull request information
-    auto pr_opt = fetch_pull_request(owner, repo, pr_number, github_token);
+    // Fetch pull/merge request information
+    auto pr_opt = fetch_pull_request(platform, owner, repo, pr_number, api_token);
     
     if (!pr_opt) {
         Json::Value error;
-        error["error"] = "Failed to fetch pull request information";
+        error["error"] = "Failed to fetch pull/merge request information";
+        error["platform"] = (platform == GitPlatform::GitHub) ? "GitHub" : "GitLab";
         error["owner"] = owner;
         error["repo"] = repo;
         error["pr_number"] = pr_number;
@@ -102,7 +105,7 @@ void PRController::resolvePR(
             // Fetch base version (empty for added files)
             std::vector<std::string> base_content;
             if (file.status == "modified") {
-                auto base_opt = fetch_file_content(owner, repo, pr.base_sha, file.filename, github_token);
+                auto base_opt = fetch_file_content(platform, owner, repo, pr.base_sha, file.filename, api_token);
                 if (!base_opt) {
                     file_result["error"] = "Failed to fetch base version";
                     file_result["had_conflicts"] = false;
@@ -114,7 +117,7 @@ void PRController::resolvePR(
             }
 
             // Fetch head version
-            auto head_opt = fetch_file_content(owner, repo, pr.head_sha, file.filename, github_token);
+            auto head_opt = fetch_file_content(platform, owner, repo, pr.head_sha, file.filename, api_token);
             if (!head_opt) {
                 file_result["error"] = "Failed to fetch head version";
                 file_result["had_conflicts"] = false;
@@ -160,6 +163,7 @@ void PRController::resolvePR(
     response["success"] = true;
     
     Json::Value pr_info;
+    pr_info["platform"] = (pr.platform == GitPlatform::GitHub) ? "GitHub" : "GitLab";
     pr_info["number"] = pr.number;
     pr_info["title"] = pr.title;
     pr_info["state"] = pr.state;

backend/src/git/git_platform_client.cpp

@@ -0,0 +1,417 @@
+/**
+ * @file git_platform_client.cpp
+ * @brief Implementation of git platform API client for GitHub and GitLab
+ */
+
+#include "wizardmerge/git/git_platform_client.h"
+#include <regex>
+#include <sstream>
+#include <iostream>
+#include <algorithm>
+#include <curl/curl.h>
+#include <json/json.h>
+
+namespace wizardmerge {
+namespace git {
+
+namespace {
+
+/**
+ * @brief Simple base64 decoder
+ */
+std::string base64_decode(const std::string& encoded) {
+    static const std::string base64_chars = 
+        "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+        "abcdefghijklmnopqrstuvwxyz"
+        "0123456789+/";
+    
+    std::string decoded;
+    std::vector<int> T(256, -1);
+    for (int i = 0; i < 64; i++) T[base64_chars[i]] = i;
+    
+    int val = 0, valb = -8;
+    for (unsigned char c : encoded) {
+        if (T[c] == -1) break;
+        val = (val << 6) + T[c];
+        valb += 6;
+        if (valb >= 0) {
+            decoded.push_back(char((val >> valb) & 0xFF));
+            valb -= 8;
+        }
+    }
+    return decoded;
+}
+
+namespace {
+
+// Callback for libcurl to write response data
+size_t WriteCallback(void* contents, size_t size, size_t nmemb, void* userp) {
+    ((std::string*)userp)->append((char*)contents, size * nmemb);
+    return size * nmemb;
+}
+
+/**
+ * @brief Perform HTTP GET request using libcurl
+ */
+bool http_get(const std::string& url, const std::string& token, std::string& response, GitPlatform platform = GitPlatform::GitHub) {
+    CURL* curl = curl_easy_init();
+    if (!curl) {
+        std::cerr << "Failed to initialize CURL" << std::endl;
+        return false;
+    }
+
+    response.clear();
+    
+    curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
+    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteCallback);
+    curl_easy_setopt(curl, CURLOPT_WRITEDATA, &response);
+    curl_easy_setopt(curl, CURLOPT_USERAGENT, "WizardMerge/1.0");
+    curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);
+    curl_easy_setopt(curl, CURLOPT_TIMEOUT, 30L);
+
+    // Setup headers based on platform
+    struct curl_slist* headers = nullptr;
+    
+    if (platform == GitPlatform::GitHub) {
+        headers = curl_slist_append(headers, "Accept: application/vnd.github.v3+json");
+        if (!token.empty()) {
+            std::string auth_header = "Authorization: token " + token;
+            headers = curl_slist_append(headers, auth_header.c_str());
+        }
+    } else if (platform == GitPlatform::GitLab) {
+        headers = curl_slist_append(headers, "Accept: application/json");
+        if (!token.empty()) {
+            std::string auth_header = "PRIVATE-TOKEN: " + token;
+            headers = curl_slist_append(headers, auth_header.c_str());
+        }
+    }
+    
+    curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
+
+    CURLcode res = curl_easy_perform(curl);
+    
+    bool success = (res == CURLE_OK);
+    if (!success) {
+        std::cerr << "CURL error: " << curl_easy_strerror(res) << std::endl;
+    }
+
+    curl_slist_free_all(headers);
+    curl_easy_cleanup(curl);
+
+    return success;
+}
+
+/**
+ * @brief Split string by newlines
+ */
+std::vector<std::string> split_lines(const std::string& content) {
+    std::vector<std::string> lines;
+    std::istringstream stream(content);
+    std::string line;
+    
+    while (std::getline(stream, line)) {
+        lines.push_back(line);
+    }
+    
+    return lines;
+}
+
+}  // anonymous namespace
+
+bool parse_pr_url(const std::string& url, GitPlatform& platform,
+                  std::string& owner, std::string& repo, int& pr_number) {
+    // Try GitHub pattern first:
+    // https://github.com/owner/repo/pull/123
+    // github.com/owner/repo/pull/123
+    
+    std::regex github_regex(R"((?:https?://)?(?:www\.)?github\.com/([^/]+)/([^/]+)/pull/(\d+))");
+    std::smatch matches;
+    
+    if (std::regex_search(url, matches, github_regex)) {
+        if (matches.size() == 4) {
+            platform = GitPlatform::GitHub;
+            owner = matches[1].str();
+            repo = matches[2].str();
+            pr_number = std::stoi(matches[3].str());
+            return true;
+        }
+    }
+    
+    // Try GitLab pattern:
+    // https://gitlab.com/owner/repo/-/merge_requests/456
+    // gitlab.com/group/subgroup/project/-/merge_requests/789
+    
+    std::regex gitlab_regex(R"((?:https?://)?(?:www\.)?gitlab\.com/([^/-]+(?:/[^/-]+)*?)/-/merge_requests/(\d+))");
+    
+    if (std::regex_search(url, matches, gitlab_regex)) {
+        if (matches.size() == 3) {
+            platform = GitPlatform::GitLab;
+            std::string full_path = matches[1].str();
+            
+            // Extract owner (group) and repo (project) from full path
+            // For GitLab, the path can be group/subgroup/project
+            // We need to split it to get the last part as repo
+            size_t last_slash = full_path.find_last_of('/');
+            if (last_slash != std::string::npos) {
+                owner = full_path.substr(0, last_slash);
+                repo = full_path.substr(last_slash + 1);
+            } else {
+                // Single level, no subgroups
+                owner = full_path;
+                repo = "";
+            }
+            
+            pr_number = std::stoi(matches[2].str());
+            return true;
+        }
+    }
+    
+    platform = GitPlatform::Unknown;
+    return false;
+}
+
+std::optional<PullRequest> fetch_pull_request(
+    GitPlatform platform,
+    const std::string& owner,
+    const std::string& repo,
+    int pr_number,
+    const std::string& token
+) {
+    PullRequest pr;
+    pr.platform = platform;
+    pr.number = pr_number;
+    pr.repo_owner = owner;
+    pr.repo_name = repo;
+    
+    std::string pr_url, files_url;
+    
+    if (platform == GitPlatform::GitHub) {
+        // GitHub API URLs
+        pr_url = "https://api.github.com/repos/" + owner + "/" + repo + "/pulls/" + std::to_string(pr_number);
+        files_url = "https://api.github.com/repos/" + owner + "/" + repo + "/pulls/" + std::to_string(pr_number) + "/files";
+    } else if (platform == GitPlatform::GitLab) {
+        // GitLab API URLs - encode project path
+        std::string project_path = owner;
+        if (!repo.empty()) {
+            project_path += "/" + repo;
+        }
+        // URL encode the project path
+        CURL* curl = curl_easy_init();
+        char* encoded = curl_easy_escape(curl, project_path.c_str(), project_path.length());
+        std::string encoded_project = encoded;
+        curl_free(encoded);
+        curl_easy_cleanup(curl);
+        
+        pr_url = "https://gitlab.com/api/v4/projects/" + encoded_project + "/merge_requests/" + std::to_string(pr_number);
+        files_url = "https://gitlab.com/api/v4/projects/" + encoded_project + "/merge_requests/" + std::to_string(pr_number) + "/changes";
+    } else {
+        std::cerr << "Unknown platform" << std::endl;
+        return std::nullopt;
+    }
+    
+    // Fetch PR/MR info
+    std::string response;
+    if (!http_get(pr_url, token, response, platform)) {
+        std::cerr << "Failed to fetch pull/merge request info" << std::endl;
+        return std::nullopt;
+    }
+
+    // Parse JSON response
+    Json::Value root;
+    Json::CharReaderBuilder reader;
+    std::string errs;
+    std::istringstream s(response);
+    
+    if (!Json::parseFromStream(reader, s, &root, &errs)) {
+        std::cerr << "Failed to parse PR/MR JSON: " << errs << std::endl;
+        return std::nullopt;
+    }
+
+    pr.title = root.get("title", "").asString();
+    pr.state = root.get("state", "").asString();
+    
+    if (platform == GitPlatform::GitHub) {
+        if (root.isMember("base") && root["base"].isObject()) {
+            pr.base_ref = root["base"].get("ref", "").asString();
+            pr.base_sha = root["base"].get("sha", "").asString();
+        }
+        
+        if (root.isMember("head") && root["head"].isObject()) {
+            pr.head_ref = root["head"].get("ref", "").asString();
+            pr.head_sha = root["head"].get("sha", "").asString();
+        }
+        
+        pr.mergeable = root.get("mergeable", false).asBool();
+        pr.mergeable_state = root.get("mergeable_state", "unknown").asString();
+    } else if (platform == GitPlatform::GitLab) {
+        pr.base_ref = root.get("target_branch", "").asString();
+        pr.head_ref = root.get("source_branch", "").asString();
+        pr.base_sha = root.get("diff_refs", Json::Value::null).get("base_sha", "").asString();
+        pr.head_sha = root.get("diff_refs", Json::Value::null).get("head_sha", "").asString();
+        
+        // GitLab uses different merge status
+        std::string merge_status = root.get("merge_status", "").asString();
+        pr.mergeable = (merge_status == "can_be_merged");
+        pr.mergeable_state = merge_status;
+    }
+
+    // Fetch PR/MR files
+    std::string files_response;
+    
+    if (!http_get(files_url, token, files_response, platform)) {
+        std::cerr << "Failed to fetch pull/merge request files" << std::endl;
+        return std::nullopt;
+    }
+
+    Json::Value files_root;
+    std::istringstream files_stream(files_response);
+    
+    if (!Json::parseFromStream(reader, files_stream, &files_root, &errs)) {
+        std::cerr << "Failed to parse files JSON: " << errs << std::endl;
+        return std::nullopt;
+    }
+
+    if (Json::parseFromStream(reader, files_stream, &files_root, &errs)) {
+        if (platform == GitPlatform::GitHub && files_root.isArray()) {
+            // GitHub format: array of file objects
+            for (const auto& file : files_root) {
+                PRFile pr_file;
+                pr_file.filename = file.get("filename", "").asString();
+                pr_file.status = file.get("status", "").asString();
+                pr_file.additions = file.get("additions", 0).asInt();
+                pr_file.deletions = file.get("deletions", 0).asInt();
+                pr_file.changes = file.get("changes", 0).asInt();
+                
+                pr.files.push_back(pr_file);
+            }
+        } else if (platform == GitPlatform::GitLab && files_root.isMember("changes")) {
+            // GitLab format: object with "changes" array
+            const Json::Value& changes = files_root["changes"];
+            if (changes.isArray()) {
+                for (const auto& file : changes) {
+                    PRFile pr_file;
+                    pr_file.filename = file.get("new_path", file.get("old_path", "").asString()).asString();
+                    
+                    // Determine status from new_file, deleted_file, renamed_file flags
+                    bool new_file = file.get("new_file", false).asBool();
+                    bool deleted_file = file.get("deleted_file", false).asBool();
+                    bool renamed_file = file.get("renamed_file", false).asBool();
+                    
+                    if (new_file) {
+                        pr_file.status = "added";
+                    } else if (deleted_file) {
+                        pr_file.status = "removed";
+                    } else if (renamed_file) {
+                        pr_file.status = "renamed";
+                    } else {
+                        pr_file.status = "modified";
+                    }
+                    
+                    // GitLab doesn't provide addition/deletion counts in the changes endpoint
+                    pr_file.additions = 0;
+                    pr_file.deletions = 0;
+                    pr_file.changes = 0;
+                    
+                    pr.files.push_back(pr_file);
+                }
+            }
+        }
+    }
+
+    return pr;
+}
+
+std::optional<std::vector<std::string>> fetch_file_content(
+    GitPlatform platform,
+    const std::string& owner,
+    const std::string& repo,
+    const std::string& sha,
+    const std::string& path,
+    const std::string& token
+) {
+    std::string url;
+    
+    if (platform == GitPlatform::GitHub) {
+        // GitHub API URL
+        url = "https://api.github.com/repos/" + owner + "/" + repo + "/contents/" + path + "?ref=" + sha;
+    } else if (platform == GitPlatform::GitLab) {
+        // GitLab API URL - encode project path and file path
+        std::string project_path = owner;
+        if (!repo.empty()) {
+            project_path += "/" + repo;
+        }
+        
+        CURL* curl = curl_easy_init();
+        char* encoded_project = curl_easy_escape(curl, project_path.c_str(), project_path.length());
+        char* encoded_path = curl_easy_escape(curl, path.c_str(), path.length());
+        
+        url = "https://gitlab.com/api/v4/projects/" + std::string(encoded_project) + 
+              "/repository/files/" + std::string(encoded_path) + "/raw?ref=" + sha;
+        
+        curl_free(encoded_project);
+        curl_free(encoded_path);
+        curl_easy_cleanup(curl);
+    } else {
+        std::cerr << "Unknown platform" << std::endl;
+        return std::nullopt;
+    }
+    
+    std::string response;
+    
+    if (!http_get(url, token, response, platform)) {
+        std::cerr << "Failed to fetch file content for " << path << " at " << sha << std::endl;
+        return std::nullopt;
+    }
+
+    // Handle response based on platform
+    if (platform == GitPlatform::GitHub) {
+        // GitHub returns JSON with base64-encoded content
+        Json::Value root;
+        Json::CharReaderBuilder reader;
+        std::string errs;
+        std::istringstream s(response);
+    
+        if (!Json::parseFromStream(reader, s, &root, &errs)) {
+            std::cerr << "Failed to parse content JSON: " << errs << std::endl;
+            return std::nullopt;
+        }
+
+        // GitHub API returns content as base64 encoded
+        if (!root.isMember("content") || !root.isMember("encoding")) {
+            std::cerr << "Invalid response format for file content" << std::endl;
+            return std::nullopt;
+        }
+
+        std::string encoding = root["encoding"].asString();
+        if (encoding != "base64") {
+            std::cerr << "Unsupported encoding: " << encoding << std::endl;
+            return std::nullopt;
+        }
+
+        // Decode base64 content
+        std::string encoded_content = root["content"].asString();
+        
+        // Remove newlines from base64 string
+        encoded_content.erase(std::remove(encoded_content.begin(), encoded_content.end(), '\n'), encoded_content.end());
+        encoded_content.erase(std::remove(encoded_content.begin(), encoded_content.end(), '\r'), encoded_content.end());
+        
+        // Decode base64
+        std::string decoded_content = base64_decode(encoded_content);
+        
+        if (decoded_content.empty()) {
+            std::cerr << "Failed to decode base64 content" << std::endl;
+            return std::nullopt;
+        }
+        
+        // Split content into lines
+        return split_lines(decoded_content);
+    } else if (platform == GitPlatform::GitLab) {
+        // GitLab returns raw file content directly
+        return split_lines(response);
+    }
+    
+    return std::nullopt;
+}
+
+}  // namespace git
+}  // namespace wizardmerge

backend/src/git/github_client.cpp

@@ -1,273 +0,0 @@
-/**
- * @file github_client.cpp
- * @brief Implementation of GitHub API client
- */
-
-#include "wizardmerge/git/github_client.h"
-#include <regex>
-#include <sstream>
-#include <iostream>
-#include <algorithm>
-#include <curl/curl.h>
-#include <json/json.h>
-
-namespace wizardmerge {
-namespace git {
-
-namespace {
-
-/**
- * @brief Simple base64 decoder
- */
-std::string base64_decode(const std::string& encoded) {
-    static const std::string base64_chars = 
-        "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
-        "abcdefghijklmnopqrstuvwxyz"
-        "0123456789+/";
-    
-    std::string decoded;
-    std::vector<int> T(256, -1);
-    for (int i = 0; i < 64; i++) T[base64_chars[i]] = i;
-    
-    int val = 0, valb = -8;
-    for (unsigned char c : encoded) {
-        if (T[c] == -1) break;
-        val = (val << 6) + T[c];
-        valb += 6;
-        if (valb >= 0) {
-            decoded.push_back(char((val >> valb) & 0xFF));
-            valb -= 8;
-        }
-    }
-    return decoded;
-}
-
-namespace {
-
-// Callback for libcurl to write response data
-size_t WriteCallback(void* contents, size_t size, size_t nmemb, void* userp) {
-    ((std::string*)userp)->append((char*)contents, size * nmemb);
-    return size * nmemb;
-}
-
-/**
- * @brief Perform HTTP GET request using libcurl
- */
-bool http_get(const std::string& url, const std::string& token, std::string& response) {
-    CURL* curl = curl_easy_init();
-    if (!curl) {
-        std::cerr << "Failed to initialize CURL" << std::endl;
-        return false;
-    }
-
-    response.clear();
-    
-    curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
-    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteCallback);
-    curl_easy_setopt(curl, CURLOPT_WRITEDATA, &response);
-    curl_easy_setopt(curl, CURLOPT_USERAGENT, "WizardMerge/1.0");
-    curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);
-    curl_easy_setopt(curl, CURLOPT_TIMEOUT, 30L);
-
-    // Setup headers
-    struct curl_slist* headers = nullptr;
-    headers = curl_slist_append(headers, "Accept: application/vnd.github.v3+json");
-    
-    if (!token.empty()) {
-        std::string auth_header = "Authorization: token " + token;
-        headers = curl_slist_append(headers, auth_header.c_str());
-    }
-    
-    curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
-
-    CURLcode res = curl_easy_perform(curl);
-    
-    bool success = (res == CURLE_OK);
-    if (!success) {
-        std::cerr << "CURL error: " << curl_easy_strerror(res) << std::endl;
-    }
-
-    curl_slist_free_all(headers);
-    curl_easy_cleanup(curl);
-
-    return success;
-}
-
-/**
- * @brief Split string by newlines
- */
-std::vector<std::string> split_lines(const std::string& content) {
-    std::vector<std::string> lines;
-    std::istringstream stream(content);
-    std::string line;
-    
-    while (std::getline(stream, line)) {
-        lines.push_back(line);
-    }
-    
-    return lines;
-}
-
-}  // anonymous namespace
-
-bool parse_pr_url(const std::string& url, std::string& owner, 
-                  std::string& repo, int& pr_number) {
-    // Match patterns like:
-    // https://github.com/owner/repo/pull/123
-    // github.com/owner/repo/pull/123
-    // owner/repo/pull/123
-    
-    std::regex pr_regex(R"((?:https?://)?(?:www\.)?github\.com/([^/]+)/([^/]+)/pull/(\d+))");
-    std::smatch matches;
-    
-    if (std::regex_search(url, matches, pr_regex)) {
-        if (matches.size() == 4) {
-            owner = matches[1].str();
-            repo = matches[2].str();
-            pr_number = std::stoi(matches[3].str());
-            return true;
-        }
-    }
-    
-    return false;
-}
-
-std::optional<PullRequest> fetch_pull_request(
-    const std::string& owner,
-    const std::string& repo,
-    int pr_number,
-    const std::string& token
-) {
-    // Fetch PR info
-    std::string pr_url = "https://api.github.com/repos/" + owner + "/" + repo + "/pulls/" + std::to_string(pr_number);
-    std::string response;
-    
-    if (!http_get(pr_url, token, response)) {
-        std::cerr << "Failed to fetch pull request info" << std::endl;
-        return std::nullopt;
-    }
-
-    // Parse JSON response
-    Json::Value root;
-    Json::CharReaderBuilder reader;
-    std::string errs;
-    std::istringstream s(response);
-    
-    if (!Json::parseFromStream(reader, s, &root, &errs)) {
-        std::cerr << "Failed to parse PR JSON: " << errs << std::endl;
-        return std::nullopt;
-    }
-
-    PullRequest pr;
-    pr.number = pr_number;
-    pr.title = root.get("title", "").asString();
-    pr.state = root.get("state", "").asString();
-    pr.repo_owner = owner;
-    pr.repo_name = repo;
-    
-    if (root.isMember("base") && root["base"].isObject()) {
-        pr.base_ref = root["base"].get("ref", "").asString();
-        pr.base_sha = root["base"].get("sha", "").asString();
-    }
-    
-    if (root.isMember("head") && root["head"].isObject()) {
-        pr.head_ref = root["head"].get("ref", "").asString();
-        pr.head_sha = root["head"].get("sha", "").asString();
-    }
-    
-    pr.mergeable = root.get("mergeable", false).asBool();
-    pr.mergeable_state = root.get("mergeable_state", "unknown").asString();
-
-    // Fetch PR files
-    std::string files_url = "https://api.github.com/repos/" + owner + "/" + repo + "/pulls/" + std::to_string(pr_number) + "/files";
-    std::string files_response;
-    
-    if (!http_get(files_url, token, files_response)) {
-        std::cerr << "Failed to fetch pull request files" << std::endl;
-        return std::nullopt;
-    }
-
-    Json::Value files_root;
-    std::istringstream files_stream(files_response);
-    
-    if (!Json::parseFromStream(reader, files_stream, &files_root, &errs)) {
-        std::cerr << "Failed to parse files JSON: " << errs << std::endl;
-        return std::nullopt;
-    }
-
-    if (files_root.isArray()) {
-        for (const auto& file : files_root) {
-            PRFile pr_file;
-            pr_file.filename = file.get("filename", "").asString();
-            pr_file.status = file.get("status", "").asString();
-            pr_file.additions = file.get("additions", 0).asInt();
-            pr_file.deletions = file.get("deletions", 0).asInt();
-            pr_file.changes = file.get("changes", 0).asInt();
-            
-            pr.files.push_back(pr_file);
-        }
-    }
-
-    return pr;
-}
-
-std::optional<std::vector<std::string>> fetch_file_content(
-    const std::string& owner,
-    const std::string& repo,
-    const std::string& sha,
-    const std::string& path,
-    const std::string& token
-) {
-    // Use GitHub API to get file content at specific commit
-    std::string url = "https://api.github.com/repos/" + owner + "/" + repo + "/contents/" + path + "?ref=" + sha;
-    std::string response;
-    
-    if (!http_get(url, token, response)) {
-        std::cerr << "Failed to fetch file content for " << path << " at " << sha << std::endl;
-        return std::nullopt;
-    }
-
-    // Parse JSON response
-    Json::Value root;
-    Json::CharReaderBuilder reader;
-    std::string errs;
-    std::istringstream s(response);
-    
-    if (!Json::parseFromStream(reader, s, &root, &errs)) {
-        std::cerr << "Failed to parse content JSON: " << errs << std::endl;
-        return std::nullopt;
-    }
-
-    // GitHub API returns content as base64 encoded
-    if (!root.isMember("content") || !root.isMember("encoding")) {
-        std::cerr << "Invalid response format for file content" << std::endl;
-        return std::nullopt;
-    }
-
-    std::string encoding = root["encoding"].asString();
-    if (encoding != "base64") {
-        std::cerr << "Unsupported encoding: " << encoding << std::endl;
-        return std::nullopt;
-    }
-
-    // Decode base64 content
-    std::string encoded_content = root["content"].asString();
-    
-    // Remove newlines from base64 string
-    encoded_content.erase(std::remove(encoded_content.begin(), encoded_content.end(), '\n'), encoded_content.end());
-    encoded_content.erase(std::remove(encoded_content.begin(), encoded_content.end(), '\r'), encoded_content.end());
-    
-    // Decode base64
-    std::string decoded_content = base64_decode(encoded_content);
-    
-    if (decoded_content.empty()) {
-        std::cerr << "Failed to decode base64 content" << std::endl;
-        return std::nullopt;
-    }
-    
-    // Split content into lines
-    return split_lines(decoded_content);
-}
-
-}  // namespace git
-}  // namespace wizardmerge

backend/tests/test_git_platform_client.cpp

@@ -0,0 +1,116 @@
+/**
+ * @file test_git_platform_client.cpp
+ * @brief Unit tests for git platform client functionality (GitHub and GitLab)
+ */
+
+#include "wizardmerge/git/git_platform_client.h"
+#include <gtest/gtest.h>
+
+using namespace wizardmerge::git;
+
+/**
+ * Test PR URL parsing with various GitHub formats
+ */
+TEST(GitPlatformClientTest, ParseGitHubPRUrl_ValidUrls) {
+    GitPlatform platform;
+    std::string owner, repo;
+    int pr_number;
+    
+    // Test full HTTPS URL
+    ASSERT_TRUE(parse_pr_url("https://github.com/owner/repo/pull/123", platform, owner, repo, pr_number));
+    EXPECT_EQ(platform, GitPlatform::GitHub);
+    EXPECT_EQ(owner, "owner");
+    EXPECT_EQ(repo, "repo");
+    EXPECT_EQ(pr_number, 123);
+    
+    // Test without https://
+    ASSERT_TRUE(parse_pr_url("github.com/user/project/pull/456", platform, owner, repo, pr_number));
+    EXPECT_EQ(platform, GitPlatform::GitHub);
+    EXPECT_EQ(owner, "user");
+    EXPECT_EQ(repo, "project");
+    EXPECT_EQ(pr_number, 456);
+    
+    // Test with www
+    ASSERT_TRUE(parse_pr_url("https://www.github.com/testuser/testrepo/pull/789", platform, owner, repo, pr_number));
+    EXPECT_EQ(platform, GitPlatform::GitHub);
+    EXPECT_EQ(owner, "testuser");
+    EXPECT_EQ(repo, "testrepo");
+    EXPECT_EQ(pr_number, 789);
+}
+
+/**
+ * Test GitLab MR URL parsing with various formats
+ */
+TEST(GitPlatformClientTest, ParseGitLabMRUrl_ValidUrls) {
+    GitPlatform platform;
+    std::string owner, repo;
+    int pr_number;
+    
+    // Test full HTTPS URL
+    ASSERT_TRUE(parse_pr_url("https://gitlab.com/owner/repo/-/merge_requests/123", platform, owner, repo, pr_number));
+    EXPECT_EQ(platform, GitPlatform::GitLab);
+    EXPECT_EQ(owner, "owner");
+    EXPECT_EQ(repo, "repo");
+    EXPECT_EQ(pr_number, 123);
+    
+    // Test with group/subgroup/project
+    ASSERT_TRUE(parse_pr_url("https://gitlab.com/group/subgroup/project/-/merge_requests/456", platform, owner, repo, pr_number));
+    EXPECT_EQ(platform, GitPlatform::GitLab);
+    EXPECT_EQ(owner, "group/subgroup");
+    EXPECT_EQ(repo, "project");
+    EXPECT_EQ(pr_number, 456);
+    
+    // Test without https://
+    ASSERT_TRUE(parse_pr_url("gitlab.com/mygroup/myproject/-/merge_requests/789", platform, owner, repo, pr_number));
+    EXPECT_EQ(platform, GitPlatform::GitLab);
+    EXPECT_EQ(owner, "mygroup");
+    EXPECT_EQ(repo, "myproject");
+    EXPECT_EQ(pr_number, 789);
+}
+
+/**
+ * Test PR/MR URL parsing with invalid formats
+ */
+TEST(GitPlatformClientTest, ParsePRUrl_InvalidUrls) {
+    GitPlatform platform;
+    std::string owner, repo;
+    int pr_number;
+    
+    // Missing PR number
+    EXPECT_FALSE(parse_pr_url("https://github.com/owner/repo/pull/", platform, owner, repo, pr_number));
+    
+    // Invalid format
+    EXPECT_FALSE(parse_pr_url("https://github.com/owner/repo", platform, owner, repo, pr_number));
+    
+    // Not a GitHub or GitLab URL
+    EXPECT_FALSE(parse_pr_url("https://bitbucket.org/owner/repo/pull-requests/123", platform, owner, repo, pr_number));
+    
+    // Empty string
+    EXPECT_FALSE(parse_pr_url("", platform, owner, repo, pr_number));
+    
+    // Wrong path for GitLab
+    EXPECT_FALSE(parse_pr_url("https://gitlab.com/owner/repo/pull/123", platform, owner, repo, pr_number));
+}
+
+/**
+ * Test PR/MR URL with special characters in owner/repo names
+ */
+TEST(GitPlatformClientTest, ParsePRUrl_SpecialCharacters) {
+    GitPlatform platform;
+    std::string owner, repo;
+    int pr_number;
+    
+    // GitHub: Underscores and hyphens
+    ASSERT_TRUE(parse_pr_url("https://github.com/my-owner_123/my-repo_456/pull/999", platform, owner, repo, pr_number));
+    EXPECT_EQ(platform, GitPlatform::GitHub);
+    EXPECT_EQ(owner, "my-owner_123");
+    EXPECT_EQ(repo, "my-repo_456");
+    EXPECT_EQ(pr_number, 999);
+    
+    // GitLab: Complex group paths
+    ASSERT_TRUE(parse_pr_url("https://gitlab.com/org-name/team-1/my_project/-/merge_requests/100", platform, owner, repo, pr_number));
+    EXPECT_EQ(platform, GitPlatform::GitLab);
+    EXPECT_EQ(owner, "org-name/team-1");
+    EXPECT_EQ(repo, "my_project");
+    EXPECT_EQ(pr_number, 100);
+}

backend/tests/test_github_client.cpp

@@ -1,69 +0,0 @@
-/**
- * @file test_github_client.cpp
- * @brief Unit tests for GitHub client functionality
- */
-
-#include "wizardmerge/git/github_client.h"
-#include <gtest/gtest.h>
-
-using namespace wizardmerge::git;
-
-/**
- * Test PR URL parsing with various formats
- */
-TEST(GitHubClientTest, ParsePRUrl_ValidUrls) {
-    std::string owner, repo;
-    int pr_number;
-    
-    // Test full HTTPS URL
-    ASSERT_TRUE(parse_pr_url("https://github.com/owner/repo/pull/123", owner, repo, pr_number));
-    EXPECT_EQ(owner, "owner");
-    EXPECT_EQ(repo, "repo");
-    EXPECT_EQ(pr_number, 123);
-    
-    // Test without https://
-    ASSERT_TRUE(parse_pr_url("github.com/user/project/pull/456", owner, repo, pr_number));
-    EXPECT_EQ(owner, "user");
-    EXPECT_EQ(repo, "project");
-    EXPECT_EQ(pr_number, 456);
-    
-    // Test with www
-    ASSERT_TRUE(parse_pr_url("https://www.github.com/testuser/testrepo/pull/789", owner, repo, pr_number));
-    EXPECT_EQ(owner, "testuser");
-    EXPECT_EQ(repo, "testrepo");
-    EXPECT_EQ(pr_number, 789);
-}
-
-/**
- * Test PR URL parsing with invalid formats
- */
-TEST(GitHubClientTest, ParsePRUrl_InvalidUrls) {
-    std::string owner, repo;
-    int pr_number;
-    
-    // Missing PR number
-    EXPECT_FALSE(parse_pr_url("https://github.com/owner/repo/pull/", owner, repo, pr_number));
-    
-    // Invalid format
-    EXPECT_FALSE(parse_pr_url("https://github.com/owner/repo", owner, repo, pr_number));
-    
-    // Not a GitHub URL
-    EXPECT_FALSE(parse_pr_url("https://gitlab.com/owner/repo/pull/123", owner, repo, pr_number));
-    
-    // Empty string
-    EXPECT_FALSE(parse_pr_url("", owner, repo, pr_number));
-}
-
-/**
- * Test PR URL with special characters in owner/repo names
- */
-TEST(GitHubClientTest, ParsePRUrl_SpecialCharacters) {
-    std::string owner, repo;
-    int pr_number;
-    
-    // Underscores and hyphens
-    ASSERT_TRUE(parse_pr_url("https://github.com/my-owner_123/my-repo_456/pull/999", owner, repo, pr_number));
-    EXPECT_EQ(owner, "my-owner_123");
-    EXPECT_EQ(repo, "my-repo_456");
-    EXPECT_EQ(pr_number, 999);
-}

spec/WizardMergeSpec.tla

@@ -15,11 +15,12 @@ EXTENDS Naturals, FiniteSets
     * Identical changes from both sides
     * Whitespace-only differences
   - Command-line interface (wizardmerge-cli)
-  - Pull request URL processing and conflict resolution:
-    * Parse GitHub PR URLs
-    * Fetch PR data via GitHub API
-    * Apply merge algorithm to PR files
-    * HTTP API endpoint for PR resolution
+  - Pull request/merge request URL processing and conflict resolution:
+    * Parse GitHub PR URLs and GitLab MR URLs
+    * Fetch PR/MR data via GitHub and GitLab APIs
+    * Apply merge algorithm to PR/MR files
+    * HTTP API endpoint for PR/MR resolution
+    * Support for multiple git platforms (GitHub and GitLab)
   
   NOT YET IMPLEMENTED (Future phases):
   - Dependency graph construction (SDG analysis)
@@ -27,26 +28,32 @@ EXTENDS Naturals, FiniteSets
   - Edge classification (safe vs. violated)
   - Fine-grained DCB (Definition-Code Block) tracking
   - Mirror mapping and matching
-  - Git branch creation for resolved PRs
+  - Git branch creation for resolved PRs/MRs
+  - Support for additional platforms (Bitbucket, etc.)
   
   The current implementation in backend/src/merge/three_way_merge.cpp provides
   a foundation for the full dependency-aware algorithm specified here. Future
   phases will enhance it with the SDG analysis, edge classification, and
   dependency-aware conflict resolution described in this specification.
   
-  PR Resolution Workflow (Phase 1.2):
-  The PR resolution feature extends the core merge algorithm to work with
-  GitHub pull requests. The workflow is:
-    1. Accept PR URL: Parse URL to extract owner, repo, and PR number
-    2. Fetch PR metadata: Use GitHub API to retrieve PR information
+  PR/MR Resolution Workflow (Phase 1.2):
+  The PR/MR resolution feature extends the core merge algorithm to work with
+  both GitHub pull requests and GitLab merge requests. The workflow is:
+    1. Accept PR/MR URL: Parse URL to detect platform and extract owner, repo, and number
+    2. Fetch PR/MR metadata: Use platform-specific API to retrieve information
     3. Fetch file versions: Retrieve base and head versions of modified files
     4. Apply merge algorithm: For each file, perform three-way merge
     5. Auto-resolve conflicts: Apply heuristic resolution where possible
     6. Return results: Provide merged content and conflict status
   
-  This workflow enables batch processing of PR conflicts using the same
+  Platform Support:
+    - GitHub: Uses GitHub API v3 with "Authorization: token" header
+    - GitLab: Uses GitLab API v4 with "PRIVATE-TOKEN" header
+    - Both platforms support public and private repositories with proper authentication
+  
+  This workflow enables batch processing of PR/MR conflicts using the same
   dependency-aware merge principles, with future integration planned for
-  automatic branch creation and PR updates.
+  automatic branch creation and PR/MR updates.
 *)
 
 (*
@@ -337,32 +344,46 @@ Inv ==
 THEOREM Spec => []Inv
 
 (***************************************************************************)
-(* Pull Request Resolution Specification (Phase 1.2)                      *)
+(* Pull Request/Merge Request Resolution Specification (Phase 1.2)        *)
 (***************************************************************************)
 
 (*
-  This section extends the core merge specification to model the PR resolution
-  workflow. It describes how WizardMerge processes GitHub pull requests to
-  identify and resolve conflicts across multiple files.
+  This section extends the core merge specification to model the PR/MR resolution
+  workflow. It describes how WizardMerge processes GitHub pull requests and
+  GitLab merge requests to identify and resolve conflicts across multiple files.
+  
+  Supported Platforms:
+    - GitHub: Uses "pull request" terminology with "/pull/" URL path
+    - GitLab: Uses "merge request" terminology with "/-/merge_requests/" URL path
 *)
 
 CONSTANTS
   (*
-    PR_FILES: the set of all files in the pull request
+    GitPlatform: the platform type - GitHub or GitLab
+  *)
+  GitPlatform,
+  
+  (*
+    PR_FILES: the set of all files in the pull/merge request
   *)
   PR_FILES,
   
   (*
-    FileStatus: maps each file to its modification status in the PR
+    FileStatus: maps each file to its modification status in the PR/MR
     Possible values: "modified", "added", "removed", "renamed"
   *)
   FileStatus,
   
   (*
-    BaseSHA, HeadSHA: commit identifiers for base and head of the PR
+    BaseSHA, HeadSHA: commit identifiers for base and head of the PR/MR
   *)
   BaseSHA, HeadSHA
 
+(*
+  Platform types - GitHub uses pull requests, GitLab uses merge requests
+*)
+ASSUME GitPlatform \in {"GitHub", "GitLab"}
+
 (*
   A file is resolvable if it was modified (not removed) and we can fetch
   both its base and head versions.