/**
 * Workspace 级「PR 文件改动说明 + 续会话 id」持久化。
 *
 * 落盘到 `<workspace>/.spx/pr-file-summaries.json`，形状 `Record<string, string>`。
 * 用前缀给两类值分命名空间，避免「文件路径」与「会话 key」相撞：
 * - `sum:${issueNumber}:${path}` → 该文件一句话改动说明（跨 push 保留，不随 head sha 失效）。
 * - `ses:${issueNumber}`         → 该工单最近一次 deepseek 生成会话的 sessionId，供下次 `--resume`。
 *
 * 文件不存在或解析失败时按空处理。
 */

import { promises as fsp } from 'node:fs'
import * as path from 'node:path'

type SummaryMap = Record<string, string>

function summaryFile(workspaceRoot: string): string {
  return path.join(workspaceRoot, '.spx', 'pr-file-summaries.json')
}

function summaryKey(issueNumber: number, filePath: string): string {
  return `sum:${issueNumber}:${filePath}`
}

function sessionKey(issueNumber: number): string {
  return `ses:${issueNumber}`
}

/** 读出整张映射；文件不存在或解析失败返回空对象。 */
async function readMap(workspaceRoot: string): Promise<SummaryMap> {
  let raw: string
  try {
    raw = await fsp.readFile(summaryFile(workspaceRoot), 'utf8')
  }
  catch {
    return {}
  }
  try {
    const parsed = JSON.parse(raw) as unknown
    if (!parsed || typeof parsed !== 'object' || Array.isArray(parsed))
      return {}
    const out: SummaryMap = {}
    for (const [k, v] of Object.entries(parsed as Record<string, unknown>)) {
      if (typeof v === 'string')
        out[k] = v
    }
    return out
  }
  catch {
    return {}
  }
}

async function writeMap(workspaceRoot: string, map: SummaryMap): Promise<void> {
  const dir = path.join(workspaceRoot, '.spx')
  await fsp.mkdir(dir, { recursive: true })
  await fsp.writeFile(summaryFile(workspaceRoot), `${JSON.stringify(map, null, 2)}\n`, 'utf8')
}

/** 读某工单全部已生成的文件说明：`{ [path]: summary }`。无则空对象。 */
export async function readFileSummaries(
  workspaceRoot: string,
  issueNumber: number,
): Promise<Record<string, string>> {
  const map = await readMap(workspaceRoot)
  const prefix = `sum:${issueNumber}:`
  const out: Record<string, string> = {}
  for (const [k, v] of Object.entries(map)) {
    if (k.startsWith(prefix))
      out[k.slice(prefix.length)] = v
  }
  return out
}

/** 写某文件的说明。空串则删除该 key。 */
export async function writeFileSummary(
  workspaceRoot: string,
  issueNumber: number,
  filePath: string,
  summary: string,
): Promise<void> {
  const map = await readMap(workspaceRoot)
  const key = summaryKey(issueNumber, filePath)
  if (summary.length > 0)
    map[key] = summary
  else
    delete map[key]
  await writeMap(workspaceRoot, map)
}

/** 读某工单最近一次生成会话的 sessionId；无则 undefined。 */
export async function readSummarySession(
  workspaceRoot: string,
  issueNumber: number,
): Promise<string | undefined> {
  const map = await readMap(workspaceRoot)
  return map[sessionKey(issueNumber)] || undefined
}

/** 写某工单续会话 sessionId。传 undefined / 空串则删除（下次从头开会话）。 */
export async function writeSummarySession(
  workspaceRoot: string,
  issueNumber: number,
  sessionId: string | undefined,
): Promise<void> {
  const map = await readMap(workspaceRoot)
  const key = sessionKey(issueNumber)
  if (sessionId && sessionId.length > 0)
    map[key] = sessionId
  else
    delete map[key]
  await writeMap(workspaceRoot, map)
}