import {
  computeMapHash,
  getCachedTags,
  getCacheStats as getCacheStatsImpl,
  invalidateCache as invalidateCacheImpl,
  loadCache,
  saveCache,
  setCachedTags,
} from './cache.js'
import { getRepoFiles } from './gitFiles.js'
import { buildGraph } from './graph.js'
import { rankFiles } from './pagerank.js'
import { initParser } from './parser.js'
import { renderMap } from './renderer.js'
import { extractTags } from './symbolExtractor.js'
import type { FileTags, RepoMapOptions, RepoMapResult, CacheStats } from './types.js'

const DEFAULT_MAX_TOKENS = 2048

/**
 * Build a structural summary of a code repository.
 *
 * Walks the repo, extracts symbols via tree-sitter, builds an IDF-weighted
 * reference graph, ranks files with PageRank, and renders a token-budgeted
 * structural summary.
 */
export async function buildRepoMap(options: RepoMapOptions = {}): Promise<RepoMapResult> {
  const startTime = Date.now()
  const root = options.root ?? process.cwd()
  const maxTokens = options.maxTokens ?? DEFAULT_MAX_TOKENS
  const focusFiles = options.focusFiles ?? []

  // Initialize tree-sitter
  await initParser()

  // Get files
  const files = options.files ?? await getRepoFiles(root)
  const totalFileCount = files.length

  // Check if we have a cached rendered map
  const mapHash = computeMapHash(files, maxTokens, focusFiles)
  const cache = loadCache(root)

  // Check if rendered map is cached (stored as a special entry)
  const renderedCacheKey = `__rendered__${mapHash}`
  const renderedEntry = cache.entries[renderedCacheKey]
  if (renderedEntry && renderedEntry.tags.length === 1) {
    const cachedResult = renderedEntry.tags[0]!
    // The cached "tag" stores the rendered map in the signature field
    // and metadata in name/line fields
    try {
      const meta = JSON.parse(cachedResult.name)
      return {
        map: cachedResult.signature,
        cacheHit: true,
        buildTimeMs: Date.now() - startTime,
        fileCount: meta.fileCount ?? 0,
        totalFileCount,
        tokenCount: meta.tokenCount ?? 0,
      }
    } catch {
      // Invalid cached data, continue with full build
    }
  }

  // Extract tags for all files (using per-file cache).
  // Separate cached hits from files needing extraction.
  const allFileTags: FileTags[] = []
  const uncachedFiles: string[] = []

  for (const file of files) {
    const cachedTags = getCachedTags(cache, file, root)
    if (cachedTags) {
      allFileTags.push({ path: file, tags: cachedTags })
    } else {
      uncachedFiles.push(file)
    }
  }

  // Process uncached files in parallel batches
  const BATCH_SIZE = 50
  for (let i = 0; i < uncachedFiles.length; i += BATCH_SIZE) {
    const batch = uncachedFiles.slice(i, i + BATCH_SIZE)
    const results = await Promise.all(
      batch.map(file => extractTags(file, root).catch(() => null))
    )
    for (let j = 0; j < results.length; j++) {
      const fileTags = results[j]
      if (fileTags) {
        allFileTags.push(fileTags)
        setCachedTags(cache, fileTags.path, root, fileTags.tags)
      }
    }
  }

  // Build graph and rank
  const graph = buildGraph(allFileTags)
  const ranked = rankFiles(graph, focusFiles)

  // Build a lookup map
  const fileTagsMap = new Map<string, FileTags>()
  for (const ft of allFileTags) {
    fileTagsMap.set(ft.path, ft)
  }

  // Render
  const { map, tokenCount, fileCount } = renderMap(ranked, fileTagsMap, maxTokens)

  // Cache the rendered result
  cache.entries[renderedCacheKey] = {
    tags: [{
      kind: 'def',
      name: JSON.stringify({ fileCount, tokenCount }),
      line: 0,
      signature: map,
    }],
    mtimeMs: Date.now(),
    size: 0,
  }

  saveCache(root, cache)

  return {
    map,
    cacheHit: false,
    buildTimeMs: Date.now() - startTime,
    fileCount,
    totalFileCount,
    tokenCount,
  }
}

/** Invalidate the disk cache for a given repo root. */
export function invalidateCache(root?: string): void {
  invalidateCacheImpl(root ?? process.cwd())
}

/** Get cache statistics for a given repo root. */
export function getCacheStats(root?: string): CacheStats {
  return getCacheStatsImpl(root ?? process.cwd())
}

// Re-export types for convenience
export type { RepoMapOptions, RepoMapResult, CacheStats } from './types.js'