import { mkdir, readdir, readFile, rename, rm, stat, writeFile } from 'node:fs/promises'
import { dirname, join, relative, sep } from 'node:path'
import { listFiles, rgAvailable } from './search-service'

export interface FileNode {
  name: string
  type: 'dir' | 'file'
  path: string
  open?: boolean
  children?: FileNode[]
}

/** Directories never walked by the fallback (rg already honors these as globs). */
const IGNORE_DIRS = new Set([
  'node_modules', '.git', 'out', 'dist', 'build', '.next', '.nuxt',
  '.cache', 'coverage', 'vendor', '.idea', '.vscode', '.helder', '.turbo',
])

const MAX_FILE_BYTES = 300_000
const MAX_INDEXED_FILES = 6000

function ignored(name: string): boolean {
  return IGNORE_DIRS.has(name) || name === '.DS_Store'
}

function looksBinary(buf: Buffer): boolean {
  const n = Math.min(buf.length, 8000)
  for (let i = 0; i < n; i++) if (buf[i] === 0) return true
  return false
}

// ---- tree from a flat path list (the rg-backed primary path) ----------------

function sortTree(node: FileNode): void {
  if (!node.children) return
  node.children.sort((a, b) => {
    if (a.type !== b.type) return a.type === 'dir' ? -1 : 1
    return a.name.localeCompare(b.name)
  })
  for (const c of node.children) sortTree(c)
}

/**
 * Build a nested tree from relative file paths (dirs first, alphabetical).
 * `dirPaths` are directories to force into the tree even when they hold no
 * files — empty folders that `rg --files` can never emit (see `listEmptyDirs`).
 */
export function buildTreeFromPaths(rootName: string, paths: string[], dirPaths: string[] = []): FileNode {
  const root: FileNode = { name: rootName, type: 'dir', path: '', open: true, children: [] }
  const dirs = new Map<string, FileNode>([['', root]])

  /** Ensure a directory node (and all its ancestors) exist; return the node. */
  function ensureDir(rel: string): FileNode {
    const existing = dirs.get(rel)
    if (existing) return existing
    const parts = rel.split('/').filter(Boolean)
    let parentPath = ''
    let parent = root
    for (let i = 0; i < parts.length; i++) {
      const curPath = parentPath ? `${parentPath}/${parts[i]}` : parts[i]
      let dir = dirs.get(curPath)
      if (!dir) {
        dir = { name: parts[i], type: 'dir', path: curPath, open: i === 0, children: [] }
        dirs.set(curPath, dir)
        parent.children!.push(dir)
      }
      parent = dir
      parentPath = curPath
    }
    return parent
  }

  for (const rel of paths) {
    const parts = rel.split('/').filter(Boolean)
    if (!parts.length) continue
    const parent = ensureDir(parts.slice(0, -1).join('/'))
    parent.children!.push({ name: parts[parts.length - 1], type: 'file', path: rel })
  }
  for (const rel of dirPaths) if (rel) ensureDir(rel)
  sortTree(root)
  return root
}

function rootName(root: string): string {
  return root.split(sep).filter(Boolean).pop() || root
}

/** Project tree. Primary: rg file list (honors gitignore + excludes) plus the
 * empty folders rg can't emit. Fallback: a plain recursive walk (when ripgrep
 * is unavailable) — that already lists empty dirs. */
export async function readTree(root: string): Promise<FileNode> {
  const [paths, emptyDirs] = await Promise.all([
    listFiles(root).catch(() => [] as string[]),
    listEmptyDirs(root).catch(() => [] as string[]),
  ])
  if (paths.length || emptyDirs.length) return buildTreeFromPaths(rootName(root), paths, emptyDirs)
  return { name: rootName(root), type: 'dir', path: '', open: true, children: await readDir(root, root, 0) }
}

/**
 * Relative paths of directories whose entire subtree holds no files
 * ("file-empty" folders). `rg --files` lists files only, so an empty folder has
 * nothing for it to emit and the Explorer would never show it until its first
 * file lands (and not even after a restart). We inject these alongside the rg
 * list so a freshly created folder shows up immediately.
 *
 * Only *file-empty* dirs are injected, never a dir that contains files: a dir
 * with files is already represented by those files (gitignore-filtered by rg),
 * so this can never resurrect a gitignored content directory. Traversal honors
 * the same IGNORE_DIRS as the fallback walk. `scope` (an absolute dir inside
 * root) restricts the walk; returned paths stay relative to root.
 */
export async function listEmptyDirs(root: string, scope?: string): Promise<string[]> {
  const out: string[] = []
  /** Walk `abs`; return whether its subtree contains at least one file. */
  async function walk(abs: string, depth: number): Promise<boolean> {
    let entries: import('node:fs').Dirent[]
    try {
      entries = await readdir(abs, { withFileTypes: true })
    } catch {
      return false
    }
    let hasFile = false
    const subdirs: string[] = []
    for (const e of entries) {
      if (ignored(e.name)) continue
      if (e.isFile()) hasFile = true
      else if (e.isDirectory()) subdirs.push(join(abs, e.name))
    }
    for (const childAbs of subdirs) {
      const childHasFile = depth < 12 ? await walk(childAbs, depth + 1) : false
      if (childHasFile) hasFile = true
      else out.push(relative(root, childAbs).split(sep).join('/'))
    }
    return hasFile
  }
  await walk(scope || root, 0)
  return out
}

/** Find the node at a root-relative path inside a tree ('' is the root). */
function findNode(tree: FileNode, rel: string): FileNode | null {
  if (rel === '') return tree
  let node: FileNode | null = tree
  for (const part of rel.split('/').filter(Boolean)) {
    node = node?.children?.find((c) => c.name === part) ?? null
    if (!node) return null
  }
  return node
}

/**
 * Fresh children for a single directory (root-relative path; '' = root). Used to
 * re-read a folder on expand/collapse so newly added/removed files show up
 * without a full tree walk. Stays consistent with the initial tree: rg-backed
 * (honors gitignore + excludes), with the recursive-walk fallback only when
 * ripgrep is unavailable.
 */
export async function readDirChildren(root: string, rel: string): Promise<FileNode[]> {
  const abs = rel ? join(root, rel) : root
  if (await rgAvailable()) {
    const [paths, emptyDirs] = await Promise.all([
      listFiles(root, abs).catch(() => [] as string[]),
      listEmptyDirs(root, abs).catch(() => [] as string[]),
    ])
    return findNode(buildTreeFromPaths(rootName(root), paths, emptyDirs), rel)?.children ?? []
  }
  return readDir(abs, root, 0)
}

async function readDir(abs: string, root: string, depth: number): Promise<FileNode[]> {
  let entries: import('node:fs').Dirent[]
  try {
    entries = await readdir(abs, { withFileTypes: true })
  } catch {
    return []
  }
  const dirs: FileNode[] = []
  const files: FileNode[] = []
  for (const e of entries) {
    if (ignored(e.name)) continue
    const childAbs = join(abs, e.name)
    const rel = relative(root, childAbs).split(sep).join('/')
    if (e.isDirectory()) {
      dirs.push({
        name: e.name, type: 'dir', path: rel, open: depth < 1,
        children: depth < 12 ? await readDir(childAbs, root, depth + 1) : [],
      })
    } else if (e.isFile()) {
      files.push({ name: e.name, type: 'file', path: rel })
    }
  }
  dirs.sort((a, b) => a.name.localeCompare(b.name))
  files.sort((a, b) => a.name.localeCompare(b.name))
  return [...dirs, ...files]
}

/** Read a single text file (relative path) → string. */
export async function readProjectFile(root: string, rel: string): Promise<string> {
  const buf = await readFile(join(root, rel))
  if (looksBinary(buf)) return ''
  return buf.toString('utf8')
}

const IMAGE_MIME: Record<string, string> = {
  png: 'image/png', jpg: 'image/jpeg', jpeg: 'image/jpeg', jfif: 'image/jpeg',
  gif: 'image/gif', webp: 'image/webp', svg: 'image/svg+xml', bmp: 'image/bmp',
  ico: 'image/x-icon', avif: 'image/avif', apng: 'image/apng',
}
const MAX_IMAGE_BYTES = 25_000_000

/** Read an image file as a `data:` URL for the viewer's <img> — the renderer
 * can't touch the filesystem, and a data URL sidesteps file:// path/escaping
 * concerns entirely. Returns '' for a non-image extension, a path escaping the
 * root, or an oversized/unreadable file. */
export async function readImageDataUrl(root: string, rel: string): Promise<string> {
  const ext = rel.split('.').pop()?.toLowerCase() ?? ''
  const mime = IMAGE_MIME[ext]
  if (!mime) return ''
  const target = join(root, rel)
  if (relative(root, target).startsWith('..')) return ''
  try {
    const buf = await readFile(target)
    if (buf.length > MAX_IMAGE_BYTES) return ''
    return `data:${mime};base64,${buf.toString('base64')}`
  } catch {
    return ''
  }
}

/** Write a text file (relative path). Used by the editable buffer's save. */
export async function writeProjectFile(root: string, rel: string, content: string): Promise<void> {
  await writeFile(join(root, rel), content, 'utf8')
}

/**
 * Create a new, empty text file (relative path). Creates parent folders as
 * needed, refuses to escape the project root, and throws if the file already
 * exists so an accidental name collision never clobbers existing content.
 */
export async function createProjectFile(root: string, rel: string): Promise<void> {
  const target = join(root, rel)
  if (relative(root, target).startsWith('..')) throw new Error('outside project root')
  const existing = await stat(target).catch(() => null)
  if (existing) throw new Error('file already exists')
  await mkdir(dirname(target), { recursive: true })
  await writeFile(target, '', { encoding: 'utf8', flag: 'wx' })
}

/**
 * Create a new, empty folder (relative path). Creates parent folders as needed,
 * refuses to escape the project root, and throws if the folder already exists so
 * a name collision is surfaced rather than silently swallowed. The empty folder
 * shows up in the tree immediately (see `listEmptyDirs`).
 */
export async function createProjectDir(root: string, rel: string): Promise<void> {
  const target = join(root, rel)
  if (relative(root, target).startsWith('..')) throw new Error('outside project root')
  const existing = await stat(target).catch(() => null)
  if (existing) throw new Error('folder already exists')
  await mkdir(target, { recursive: true })
}

/**
 * Rename a project file or folder. `rel` is the current relative path, `name`
 * the new basename (no slashes — a rename stays in the same folder). Returns the
 * new relative path. Refuses to escape the project root and throws if the target
 * name is already taken, so a rename never clobbers an existing file.
 */
export async function renameProjectEntry(root: string, rel: string, name: string): Promise<string> {
  const clean = name.trim().replace(/\/+$/, '')
  if (!clean || clean.includes('/') || clean === '.' || clean === '..') throw new Error('invalid name')
  const from = join(root, rel)
  const parent = rel.includes('/') ? rel.slice(0, rel.lastIndexOf('/')) : ''
  const next = parent ? `${parent}/${clean}` : clean
  const to = join(root, next)
  if (relative(root, from).startsWith('..') || relative(root, to).startsWith('..')) throw new Error('outside project root')
  if (from === to) return rel
  // Case-only renames (foo.md → Foo.md) hit an existing path on macOS' case
  // insensitive filesystem, so only guard when the name really differs.
  const sameName = from.toLowerCase() === to.toLowerCase()
  if (!sameName && await stat(to).catch(() => null)) throw new Error('name already exists')
  await rename(from, to)
  return next
}

/** Delete a project file or folder (relative path). Stays inside the project root. */
export async function deleteProjectFile(root: string, rel: string): Promise<void> {
  const target = join(root, rel)
  if (relative(root, target).startsWith('..')) return // guard against escaping the root
  await rm(target, { recursive: true, force: true })
}

/**
 * In-memory content index of all (small, text) files — powers content viewing.
 * Primary: read the rg file list; fallback: walk. Capped for large repos.
 */
export async function readAll(root: string): Promise<Record<string, string>> {
  const paths = await listFiles(root).catch(() => [] as string[])
  if (paths.length) return readListed(root, paths)
  return readAllWalk(root)
}

async function readListed(root: string, paths: string[]): Promise<Record<string, string>> {
  const out: Record<string, string> = {}
  let count = 0
  for (const rel of paths) {
    if (count >= MAX_INDEXED_FILES) break
    try {
      const abs = join(root, rel)
      const s = await stat(abs)
      if (s.size > MAX_FILE_BYTES) continue
      const buf = await readFile(abs)
      if (looksBinary(buf)) continue
      out[rel] = buf.toString('utf8')
      count++
    } catch {
      /* skip unreadable */
    }
  }
  return out
}

async function readAllWalk(root: string): Promise<Record<string, string>> {
  const out: Record<string, string> = {}
  let count = 0
  async function walk(abs: string): Promise<void> {
    if (count >= MAX_INDEXED_FILES) return
    let entries: import('node:fs').Dirent[]
    try {
      entries = await readdir(abs, { withFileTypes: true })
    } catch {
      return
    }
    for (const e of entries) {
      if (count >= MAX_INDEXED_FILES) return
      if (ignored(e.name)) continue
      const childAbs = join(abs, e.name)
      if (e.isDirectory()) {
        await walk(childAbs)
      } else if (e.isFile()) {
        try {
          const s = await stat(childAbs)
          if (s.size > MAX_FILE_BYTES) continue
          const buf = await readFile(childAbs)
          if (looksBinary(buf)) continue
          out[relative(root, childAbs).split(sep).join('/')] = buf.toString('utf8')
          count++
        } catch {
          /* skip unreadable */
        }
      }
    }
  }
  await walk(root)
  return out
}