import {readFileSync, writeFileSync, existsSync, statSync} from 'fs'
import {join, dirname} from 'path'
import {Symbol, DependencyEdge, SymbolGraph} from './symbol-graph'

export interface FileCacheEntry {
  mtime: number
  size: number
  contentHash: string
  symbols: Symbol[]
  edges: DependencyEdge[]
  parsedAt: number
}

export interface GraphCache {
  version: string
  repoPath: string
  lastUpdated: number
  fileEntries: Map<string, FileCacheEntry>
  globalEdges: DependencyEdge[]
}

const CACHE_VERSION = '2.0.0'

function getPersistBaseDir(): string {
  if (process.env.PRIX_DATA_DIR) return process.env.PRIX_DATA_DIR
  if (process.env.HF_HOME) return join(process.env.HF_HOME, 'prix-data')
  if (process.env.HUGGING_FACE_HUB_TOKEN) return '/tmp/prix-hf'
  return '/tmp/prix'
}

export class SymbolGraphCache {
  private cache: Map<string, FileCacheEntry> = new Map()
  private repoPath: string
  private persistPath: string
  private cacheHits = 0
  private cacheMisses = 0

  constructor(repoPath: string, persistDir?: string) {
    this.repoPath = repoPath
    const baseDir = persistDir || getPersistBaseDir()
    this.persistPath = join(baseDir, 'symbol-graph-cache')
    this.load()
  }

  get(file: string): FileCacheEntry | undefined {
    if (!existsSync(file)) return undefined

    try {
      const stats = statSync(file)
      const cached = this.cache.get(file)

      if (!cached) {
        this.cacheMisses++
        return undefined
      }

      if (cached.mtime !== stats.mtimeMs || cached.size !== stats.size) {
        this.cacheMisses++
        this.cache.delete(file)
        return undefined
      }

      this.cacheHits++
      return cached
    } catch {
      return undefined
    }
  }

  set(file: string, entry: FileCacheEntry): void {
    this.cache.set(file, entry)
  }

  invalidate(file: string): void {
    this.cache.delete(file)
  }

  invalidateContaining(changedFiles: string[]): Set<string> {
    const affectedFiles = new Set<string>()
    const changedSet = new Set(changedFiles.map(f => this.normalizePath(f)))

    for (const cachedFile of this.cache.keys()) {
      const normalizedCached = this.normalizePath(cachedFile)

      if (changedSet.has(normalizedCached)) {
        affectedFiles.add(cachedFile)
        continue
      }

      const cached = this.cache.get(cachedFile)
      if (!cached) continue

      for (const edge of cached.edges) {
        const normalizedEdge = this.normalizePath(edge.to)
        if (changedSet.has(normalizedEdge)) {
          affectedFiles.add(cachedFile)
          break
        }

        const normalizedFrom = this.normalizePath(edge.from)
        if (changedSet.has(normalizedFrom)) {
          affectedFiles.add(cachedFile)
          break
        }
      }

      for (const symbol of cached.symbols) {
        for (const imp of symbol.imports) {
          const normalizedImp = this.normalizeImport(imp)
          if (this.pathMatchesImport(normalizedImp, changedSet)) {
            affectedFiles.add(cachedFile)
            break
          }
        }
      }
    }

    for (const affected of affectedFiles) {
      this.cache.delete(affected)
    }

    return affectedFiles
  }

  private normalizePath(p: string): string {
    return p.replace(/\\/g, '/').toLowerCase()
  }

  private normalizeImport(imp: string): string {
    return imp.replace(/['"]/g, '').replace(/\\/g, '/').toLowerCase()
  }

  private pathMatchesImport(imp: string, changedSet: Set<string>): boolean {
    for (const changed of changedSet) {
      if (imp.endsWith(changed) || changed.endsWith(imp)) {
        return true
      }
      const impParts = imp.split('/')
      const changedParts = changed.split('/')
      if (
        impParts[impParts.length - 1] === changedParts[changedParts.length - 1]
      ) {
        return true
      }
    }
    return false
  }

  getStats(): {hits: number; misses: number; size: number; hitRate: number} {
    const total = this.cacheHits + this.cacheMisses
    return {
      hits: this.cacheHits,
      misses: this.cacheMisses,
      size: this.cache.size,
      hitRate: total > 0 ? this.cacheHits / total : 0
    }
  }

  prune(maxAge: number = 7 * 24 * 60 * 60 * 1000): number {
    const now = Date.now()
    let pruned = 0

    for (const [file, entry] of this.cache.entries()) {
      if (now - entry.parsedAt > maxAge) {
        this.cache.delete(file)
        pruned++
      }
    }

    return pruned
  }

  clear(): void {
    this.cache.clear()
    this.cacheHits = 0
    this.cacheMisses = 0
  }

  persist(): void {
    try {
      const {mkdirSync, writeFileSync, existsSync} = require('fs')
      if (!existsSync(this.persistPath)) {
        mkdirSync(this.persistPath, {recursive: true})
      }

      const cacheData: any = {
        version: CACHE_VERSION,
        repoPath: this.repoPath,
        lastUpdated: Date.now(),
        entries: Array.from(this.cache.entries())
      }

      const cacheFile = join(
        this.persistPath,
        `${this.sanitizeFilename(this.repoPath)}.json`
      )
      writeFileSync(cacheFile, JSON.stringify(cacheData), 'utf8')
    } catch (e) {
      console.warn(`Failed to persist graph cache: ${e}`)
    }
  }

  private load(): void {
    try {
      const {readFileSync, existsSync} = require('fs')
      const cacheFile = join(
        this.persistPath,
        `${this.sanitizeFilename(this.repoPath)}.json`
      )

      if (!existsSync(cacheFile)) return

      const data = JSON.parse(readFileSync(cacheFile, 'utf8'))

      if (data.version !== CACHE_VERSION) {
        console.log('Graph cache version mismatch, rebuilding...')
        return
      }

      if (data.repoPath !== this.repoPath) {
        console.log('Repo path changed, rebuilding...')
        return
      }

      const entries = new Map<string, FileCacheEntry>(data.entries)
      this.cache = entries
    } catch (e) {
      console.warn(`Failed to load graph cache: ${e}`)
    }
  }

  private sanitizeFilename(path: string): string {
    return path.replace(/[\/\\]/g, '_').substring(0, 100)
  }

  rebuildIfNeeded(changedFiles: string[]): {
    rebuild: boolean
    filesToRebuild: Set<string>
  } {
    if (changedFiles.length === 0) {
      return {rebuild: false, filesToRebuild: new Set()}
    }

    const filesToRebuild = this.invalidateContaining(changedFiles)

    return {
      rebuild: filesToRebuild.size > 0 || this.cache.size === 0,
      filesToRebuild
    }
  }
}

export interface IncrementalUpdateResult {
  updatedFiles: string[]
  removedSymbols: number
  addedSymbols: number
  cacheStats: {hits: number; misses: number; hitRate: number}
}

export class IncrementalSymbolGraph {
  private cache: SymbolGraphCache
  private graph: SymbolGraph
  private pendingUpdates: Map<string, boolean> = new Map()

  constructor(repoPath: string, persistDir?: string) {
    this.cache = new SymbolGraphCache(repoPath, persistDir)
    this.graph = {
      symbols: new Map(),
      edges: [],
      fileIndex: new Map()
    }
  }

  async update(
    changedFiles: string[],
    deletedFiles: string[]
  ): Promise<IncrementalUpdateResult> {
    for (const file of deletedFiles) {
      this.removeFile(file)
    }

    const {filesToRebuild} = this.cache.rebuildIfNeeded(changedFiles)

    let removedSymbols = 0
    let addedSymbols = 0

    for (const file of filesToRebuild) {
      const removed = this.removeFile(file)
      removedSymbols += removed
    }

    for (const file of changedFiles) {
      if (existsSync(file)) {
        const added = await this.addOrUpdateFile(file)
        addedSymbols += added
      }
    }

    this.cache.persist()

    return {
      updatedFiles: [...filesToRebuild, ...changedFiles].filter(f =>
        existsSync(f)
      ),
      removedSymbols,
      addedSymbols,
      cacheStats: this.cache.getStats()
    }
  }

  private removeFile(file: string): number {
    const cached = this.cache.get(file)
    if (cached) {
      for (const symbol of cached.symbols) {
        this.graph.symbols.delete(`${file}:${symbol.name}`)
      }
      this.graph.fileIndex.delete(file)
      this.graph.edges = this.graph.edges.filter(
        e => !e.from.startsWith(file) && !e.to.startsWith(file)
      )
      this.cache.invalidate(file)
      return cached.symbols.length
    }
    return 0
  }

  private async addOrUpdateFile(file: string): Promise<number> {
    const existing = this.cache.get(file)
    if (existing) {
      for (const symbol of existing.symbols) {
        this.graph.symbols.set(`${file}:${symbol.name}`, symbol)
      }
      this.graph.fileIndex.set(file, existing.symbols)
      this.graph.edges.push(...existing.edges)
      return existing.symbols.length
    }
    return 0
  }

  getGraph(): SymbolGraph {
    return this.graph
  }

  getCacheStats() {
    return this.cache.getStats()
  }

  clearCache(): void {
    this.cache.clear()
    this.graph = {
      symbols: new Map(),
      edges: [],
      fileIndex: new Map()
    }
  }

  persist(): void {
    this.cache.persist()
  }
}

export const createIncrementalGraph = (
  repoPath: string,
  persistDir?: string
): IncrementalSymbolGraph => {
  return new IncrementalSymbolGraph(repoPath, persistDir)
}