-- Export theme to CSS custom properties
-- Generates CSS variable declarations from theme config

---@class ToCss
local M = {}

---Generate CSS color variables
---@param colors ColorPalette Color palette
---@return string css CSS variable declarations
local function generate_color_variables(colors)
  local lines = {
    "  /* Color Variables */",
    "  --color-primary: " .. colors.primary.hex .. ";",
    "  --color-secondary: " .. colors.secondary.hex .. ";",
    "  --color-background: " .. colors.background.hex .. ";",
    "  --color-surface: " .. colors.surface.hex .. ";",
    "  --color-text-primary: " .. colors.text_primary.hex .. ";",
    "  --color-text-secondary: " .. colors.text_secondary.hex .. ";",
    "  --color-error: " .. colors.error.hex .. ";",
    "  --color-warning: " .. colors.warning.hex .. ";",
    "  --color-success: " .. colors.success.hex .. ";",
    "  --color-info: " .. colors.info.hex .. ";"
  }
  return table.concat(lines, "\n")
end

---Generate CSS typography variables
---@param typography TypographyConfig Typography config
---@return string css CSS variable declarations
local function generate_typography_variables(typography)
  local lines = {
    "",
    "  /* Typography Variables */",
    "  --font-family: '" .. typography.fontFamily .. "', sans-serif;",
    "  --font-family-heading: '" .. typography.headingFont .. "', sans-serif;",
    "  --font-family-code: '" .. typography.codeFont .. "', monospace;",
    "  --font-size-base: " .. typography.baseFontSize .. "px;"
  }
  return table.concat(lines, "\n")
end

---Generate CSS spacing variables
---@param spacing SpacingConfig Spacing config
---@return string css CSS variable declarations
local function generate_spacing_variables(spacing)
  local unit = spacing.spacingUnit
  local lines = {
    "",
    "  /* Spacing Variables */",
    "  --spacing-unit: " .. unit .. "px;",
    "  --spacing-xs: " .. (unit * 0.5) .. "px;",
    "  --spacing-sm: " .. unit .. "px;",
    "  --spacing-md: " .. (unit * 2) .. "px;",
    "  --spacing-lg: " .. (unit * 3) .. "px;",
    "  --spacing-xl: " .. (unit * 4) .. "px;",
    "  --border-radius: " .. spacing.borderRadius .. "px;",
    "  --container-width: " .. spacing.containerWidth .. "px;"
  }
  return table.concat(lines, "\n")
end

---Generate CSS border variables
---@param borders BorderConfig Border config
---@return string css CSS variable declarations
local function generate_border_variables(borders)
  local lines = {
    "",
    "  /* Border Variables */",
    "  --border-width: " .. borders.width .. "px;",
    "  --border-color: " .. borders.color.hex .. ";",
    "  --border-style: " .. borders.style .. ";"
  }
  return table.concat(lines, "\n")
end

---Generate CSS shadow variables
---@param shadows ShadowConfig Shadow config
---@return string css CSS variable declarations
local function generate_shadow_variables(shadows)
  local opacity = shadows.opacity / 100
  local offsetX = shadows.offsetX or 0
  local offsetY = shadows.offsetY or 2
  local lines = {
    "",
    "  /* Shadow Variables */",
    "  --shadow-blur: " .. shadows.blur .. "px;",
    "  --shadow-spread: " .. shadows.spread .. "px;",
    "  --shadow-opacity: " .. opacity .. ";",
    "  --shadow-default: " .. offsetX .. "px " .. offsetY .. "px " .. shadows.blur .. "px " .. shadows.spread .. "px rgba(0, 0, 0, " .. opacity .. ");"
  }
  return table.concat(lines, "\n")
end

---Generate all CSS variables from theme config
---@param theme ThemeConfig Theme configuration
---@return string css Complete CSS :root block content
function M.generate_css_variables(theme)
  local sections = {
    "/* Generated by CSS Designer */",
    "/* Theme: " .. theme.name .. " */",
    "",
    ":root {",
    generate_color_variables(theme.colors),
    generate_typography_variables(theme.typography),
    generate_spacing_variables(theme.spacing),
    generate_border_variables(theme.borders),
    generate_shadow_variables(theme.shadows),
    "}"
  }
  return table.concat(sections, "\n")
end

---Export theme to CSS
---@param theme ThemeConfig Theme configuration
---@return ThemeExport export Export result with css field populated
function M.to_css(theme)
  return {
    scss = "",
    css = M.generate_css_variables(theme),
    json = ""
  }
end

return M