/**
 * Vite Plugin Setup for Sykehuspartner Slidev Theme
 * 
 * This plugin automatically resolves relative image paths in frontmatter
 * so they work correctly after build. Without this, images referenced in
 * frontmatter like `imageSrc: ./image.png` would break after build because
 * Vite can't statically analyze frontmatter values.
 * 
 * The plugin intercepts the frontmatter virtual modules generated by Slidev
 * and transforms relative image paths into proper imports.
 */
import { defineVitePluginsSetup } from '@slidev/types'
import type { Plugin } from 'vite'
import { resolve, dirname, isAbsolute } from 'node:path'
import { existsSync } from 'node:fs'

// Image properties that should be resolved in frontmatter
const IMAGE_PROPS = [
  'imageSrc',
  'background',
  'image',
]

// Supported image extensions
const IMAGE_EXTENSIONS = ['png', 'jpg', 'jpeg', 'gif', 'svg', 'webp', 'avif', 'ico']
const IMAGE_EXT_PATTERN = IMAGE_EXTENSIONS.join('|')

export default defineVitePluginsSetup((options) => {
  const { userRoot, data } = options
  
  /**
   * Plugin that transforms frontmatter image paths into imports
   */
  const frontmatterImagePlugin: Plugin = {
    name: 'slidev-theme-sykehuspartner:frontmatter-images',
    enforce: 'post', // Run after Slidev's loader generates the frontmatter module
    
    transform(code, id) {
      // Only process frontmatter virtual modules from Slidev
      if (!id.includes('__slidev_') || !id.endsWith('.frontmatter')) {
        return null
      }

      // Find the slide's markdown file path to resolve relative images
      const slideMatch = id.match(/(.+?)__slidev_(\d+)\.frontmatter$/)
      if (!slideMatch) return null
      
      const mdFilePath = slideMatch[1]
      const mdDir = dirname(mdFilePath)
      
      // Regex to find relative image paths in frontmatter properties
      // Matches: "imageSrc": "./image.png" or 'imageSrc': './image.png'
      // Also matches paths without ./ prefix like "image.png"
      const relativePathRegex = new RegExp(
        `(["'])((?:\\.\\/|\\.\\.\\/|(?![/]|https?:|data:))[^"']*\\.(${IMAGE_EXT_PATTERN}))\\1`,
        'gi'
      )
      
      const matches = [...code.matchAll(relativePathRegex)]
      
      if (matches.length === 0) {
        return null
      }
      
      // Track unique imports to avoid duplicates
      const imports: Map<string, string> = new Map()
      let importIndex = 0
      let newCode = code
      
      for (const match of matches) {
        const fullMatch = match[0]
        const quote = match[1]
        const relativePath = match[2]
        
        // Resolve the absolute path to check if file exists
        const absolutePath = resolve(mdDir, relativePath)
        
        // Only transform if the file actually exists
        if (!existsSync(absolutePath)) {
          console.warn(`[slidev-theme-sykehuspartner] Image not found: ${relativePath} (resolved to ${absolutePath})`)
          continue
        }
        
        // Get or create import variable name for this path
        let varName = imports.get(relativePath)
        if (!varName) {
          varName = `__spImg${importIndex++}`
          imports.set(relativePath, varName)
        }
        
        // Replace the string path with the import variable
        // "imageSrc": "./image.png" becomes "imageSrc": __spImg0
        newCode = newCode.replace(fullMatch, varName)
      }
      
      if (imports.size === 0) {
        return null
      }
      
      // Generate import statements
      const importStatements = Array.from(imports.entries())
        .map(([path, varName]) => `import ${varName} from "${path}"`)
        .join('\n')
      
      // Prepend imports to the module code
      const transformedCode = importStatements + '\n' + newCode
      
      return {
        code: transformedCode,
        map: null, // Source map not needed for this transformation
      }
    },
  }
  
  /**
   * Plugin that ensures images referenced in layouts are resolved correctly
   * This handles the case where images are passed as props to layout components
   */
  const layoutImagePlugin: Plugin = {
    name: 'slidev-theme-sykehuspartner:layout-images',
    enforce: 'pre',
    
    async resolveId(source, importer) {
      // Only process if importer is a markdown slide file
      if (!importer || !importer.includes('__slidev_')) {
        return null
      }
      
      // Check if this looks like a relative image path
      const isRelativePath = source.startsWith('./') || source.startsWith('../')
      const isImageFile = new RegExp(`\\.(${IMAGE_EXT_PATTERN})$`, 'i').test(source)
      
      if (isRelativePath && isImageFile) {
        // Find the original markdown file path
        const mdMatch = importer.match(/(.+?)__slidev_\d+/)
        if (mdMatch) {
          const mdDir = dirname(mdMatch[1])
          const resolved = resolve(mdDir, source)
          if (existsSync(resolved)) {
            return resolved
          }
        }
      }
      
      return null
    },
  }
  
  return [
    frontmatterImagePlugin,
    layoutImagePlugin,
  ]
})