import { join } from "path"
import { rename } from "fs/promises"

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

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)
}