import { join, basename, dirname, resolve } from "path"
import { readdir, rename } from "fs/promises"
import { homedir } from "os"

export interface Session {
  branch: string
  worktree: string
  created_at: string
  prompt?: string
  in_review?: boolean
}

export interface State {
  sessions: Record<string, Session>
}

function statePath(repoRoot: string): string {
  return join(repoRoot, ".sandlot", "state.json")
}

export async function load(repoRoot: string): Promise<State> {
  const path = statePath(repoRoot)
  const file = Bun.file(path)
  if (await file.exists()) {
    return await file.json()
  }
  return { sessions: {} }
}

export async function save(repoRoot: string, state: State): Promise<void> {
  const path = statePath(repoRoot)
  const tmpPath = path + ".tmp"
  const dir = join(repoRoot, ".sandlot")
  await Bun.write(join(dir, ".gitkeep"), "") // ensure dir exists
  await Bun.write(tmpPath, JSON.stringify(state, null, 2) + "\n")
  await rename(tmpPath, path)
  await registerProject(repoRoot).catch(() => {})
}

export async function getSession(repoRoot: string, branch: string): Promise<Session | undefined> {
  const state = await load(repoRoot)
  return state.sessions[branch]
}

export async function setSession(repoRoot: string, session: Session): Promise<void> {
  const state = await load(repoRoot)
  state.sessions[session.branch] = session
  await save(repoRoot, state)
}

export async function removeSession(repoRoot: string, branch: string): Promise<void> {
  const state = await load(repoRoot)
  delete state.sessions[branch]
  await save(repoRoot, state)
}

// ── Global state: ~/.sandlot/state.json ──────────────────────────────

interface GlobalState {
  projects: string[]  // repo root paths
}

function globalStatePath(): string {
  return join(homedir(), ".sandlot", "state.json")
}

async function loadGlobal(): Promise<GlobalState> {
  const file = Bun.file(globalStatePath())
  if (await file.exists()) {
    return await file.json()
  }
  return { projects: [] }
}

async function saveGlobal(gs: GlobalState): Promise<void> {
  const path = globalStatePath()
  const tmpPath = path + ".tmp"
  await Bun.write(tmpPath, JSON.stringify(gs, null, 2) + "\n")
  await rename(tmpPath, path)
}

/** Register a project directory in the global state. */
export async function registerProject(repoRoot: string): Promise<void> {
  const gs = await loadGlobal()
  if (!gs.projects.includes(repoRoot)) {
    gs.projects.push(repoRoot)
    await saveGlobal(gs)
  }
}

/** Remove a project directory from the global state. */
export async function unregisterProject(dir: string): Promise<boolean> {
  const target = resolve(dir.replace(/^~/, homedir()))
  const gs = await loadGlobal()
  const idx = gs.projects.indexOf(target)
  if (idx === -1) return false
  gs.projects.splice(idx, 1)
  await saveGlobal(gs)
  return true
}

/** Recursively scan a directory for .sandlot dirs and register their parent projects. */
export async function scanAndRegister(dir: string): Promise<string[]> {
  const root = resolve(dir.replace(/^~/, homedir()))
  const registered: string[] = []

  async function walk(d: string) {
    let entries
    try {
      entries = await readdir(d, { withFileTypes: true })
    } catch {
      return
    }

    const hasSandlot = entries.some(e => e.isDirectory() && e.name === ".sandlot")
    if (hasSandlot) {
      // Verify it has a state.json
      const stateFile = Bun.file(join(d, ".sandlot", "state.json"))
      if (await stateFile.exists()) {
        await registerProject(d)
        registered.push(d)
      }
    }

    for (const entry of entries) {
      if (!entry.isDirectory() || entry.name.startsWith(".") || entry.name === "node_modules") continue
      await walk(join(d, entry.name))
    }
  }

  await walk(root)
  return registered
}

export interface GlobalSession extends Session {
  repo: string
}

/** Load all sessions across all registered projects. */
export async function loadAll(): Promise<GlobalSession[]> {
  const gs = await loadGlobal()
  const all: GlobalSession[] = []

  for (const project of gs.projects) {
    try {
      const st = await load(project)
      const repo = basename(project)
      for (const session of Object.values(st.sessions)) {
        all.push({ ...session, repo })
      }
    } catch {}
  }

  return all
}