import { join, dirname } 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)
}

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)
}

export interface GlobalSession extends Session {
  repoRoot: string
}

/** Discover all sessions across all repos by scanning ~/.sandlot/ */
export async function loadAll(): Promise<GlobalSession[]> {
  const sandlotDir = join(homedir(), ".sandlot")
  const all: GlobalSession[] = []

  let repoDirs
  try {
    repoDirs = await readdir(sandlotDir, { withFileTypes: true })
  } catch {
    return []
  }

  for (const entry of repoDirs) {
    if (!entry.isDirectory() || entry.name.startsWith(".")) continue
    const repoDir = join(sandlotDir, entry.name)

    // Find the main repo root from a worktree's .git pointer
    let repoRoot: string | null = null
    const branchEntries = await readdir(repoDir, { withFileTypes: true }).catch(() => [])

    for (const be of branchEntries) {
      if (!be.isDirectory() || be.name.startsWith(".")) continue
      const dotGit = await Bun.file(join(repoDir, be.name, ".git")).text().catch(() => "")
      const m = dotGit.match(/^gitdir:\s*(.+)/m)
      if (m) {
        // gitdir: /path/to/repo/.git/worktrees/<name>
        const mainGit = m[1].trim().replace(/\/worktrees\/[^/]+$/, "")
        repoRoot = dirname(mainGit)
        break
      }
    }

    if (repoRoot) {
      try {
        const st = await load(repoRoot)
        for (const session of Object.values(st.sessions)) {
          all.push({ ...session, repoRoot })
        }
      } catch {}
    }
  }

  return all
}