/**
 * 应用配置持久化。
 *
 * - 落盘位置：userData/config.json
 * - API Key 优先用 Electron safeStorage 加密（Windows 走 DPAPI），
 *   若系统不支持则降级为明文并在 UI 上如实标注。
 * - 渲染进程只能拿到 GatewayConfigView（无明文 Key）。
 */

import { app, safeStorage } from 'electron'
import { promises as fs } from 'node:fs'
import { join } from 'node:path'
import type { GatewayConfig, GatewayConfigView } from '@shared/types'

interface StoredConfig {
  speechBaseUrl?: string
  speechModel?: string
  baseUrl: string
  model: string
  temperature: number
  maxToolRounds: number
  apiKeyEnc?: string
  apiKeyPlain?: string
  workspaceRoot?: string
}

const DEFAULTS: StoredConfig = {
  baseUrl: 'https://api.deepseek.com/v1',
  model: 'deepseek-chat',
  temperature: 0.7,
  maxToolRounds: 6
}

let cache: StoredConfig | null = null

function filePath(): string {
  return join(app.getPath('userData'), 'config.json')
}

async function load(): Promise<StoredConfig> {
  if (cache) return cache
  try {
    const raw = await fs.readFile(filePath(), 'utf8')
    cache = { ...DEFAULTS, ...(JSON.parse(raw) as Partial<StoredConfig>) }
  } catch {
    cache = { ...DEFAULTS }
  }
  return cache
}

async function persist(next: StoredConfig): Promise<void> {
  cache = next
  const file = filePath()
  await fs.mkdir(join(file, '..'), { recursive: true })
  await fs.writeFile(file, JSON.stringify(next, null, 2), 'utf8')
}

function decryptKey(stored: StoredConfig): { key: string; storage: 'encrypted' | 'plaintext' | 'none' } {
  if (stored.apiKeyEnc) {
    try {
      return { key: safeStorage.decryptString(Buffer.from(stored.apiKeyEnc, 'base64')), storage: 'encrypted' }
    } catch {
      return { key: '', storage: 'none' }
    }
  }
  if (stored.apiKeyPlain) return { key: stored.apiKeyPlain, storage: 'plaintext' }
  return { key: '', storage: 'none' }
}

/** 供主进程内部使用：拿到可直接请求上游的完整配置 */
export async function getGatewayConfig(): Promise<GatewayConfig> {
  const stored = await load()
  const { key } = decryptKey(stored)
  return {
    speechBaseUrl: stored.speechBaseUrl,
    speechModel: stored.speechModel,
    baseUrl: stored.baseUrl,
    model: stored.model,
    temperature: stored.temperature,
    maxToolRounds: stored.maxToolRounds,
    apiKey: key
  }
}

export async function getWorkspaceRoot(): Promise<string> {
  const stored = await load()
  return stored.workspaceRoot || join(app.getPath('home'), 'YCodeWorkspace')
}

export async function setWorkspaceRoot(root: string): Promise<void> {
  const stored = await load()
  await persist({ ...stored, workspaceRoot: root })
}

/** 供渲染进程使用：脱敏视图 */
export async function getConfigView(): Promise<GatewayConfigView> {
  const stored = await load()
  const { key, storage } = decryptKey(stored)
  return {
    speechBaseUrl: stored.speechBaseUrl,
    speechModel: stored.speechModel,
    baseUrl: stored.baseUrl,
    model: stored.model,
    temperature: stored.temperature,
    maxToolRounds: stored.maxToolRounds,
    hasApiKey: key.length > 0,
    keyStorage: key.length > 0 ? storage : 'none'
  }
}

export interface ConfigPatch {
  speechBaseUrl?: string
  speechModel?: string
  baseUrl?: string
  model?: string
  temperature?: number
  maxToolRounds?: number
  /** 传空字符串表示清除 Key；不传表示保持原值 */
  apiKey?: string
}

export async function updateConfig(patch: ConfigPatch): Promise<GatewayConfigView> {
  const stored = await load()
  const next: StoredConfig = { ...stored }

  if (patch.speechBaseUrl !== undefined) next.speechBaseUrl = patch.speechBaseUrl.trim()
  if (patch.speechModel !== undefined) next.speechModel = patch.speechModel.trim()

  if (patch.baseUrl !== undefined) next.baseUrl = patch.baseUrl.trim()
  if (patch.model !== undefined) next.model = patch.model.trim()
  if (patch.temperature !== undefined) next.temperature = clamp(patch.temperature, 0, 2)
  if (patch.maxToolRounds !== undefined) next.maxToolRounds = clamp(Math.round(patch.maxToolRounds), 1, 24)

  if (patch.apiKey !== undefined) {
    const key = patch.apiKey.trim()
    if (!key) {
      delete next.apiKeyEnc
      delete next.apiKeyPlain
    } else if (safeStorage.isEncryptionAvailable()) {
      next.apiKeyEnc = safeStorage.encryptString(key).toString('base64')
      delete next.apiKeyPlain
    } else {
      next.apiKeyPlain = key
      delete next.apiKeyEnc
    }
  }

  await persist(next)
  return getConfigView()
}

function clamp(value: number, min: number, max: number): number {
  if (Number.isNaN(value)) return min
  return Math.min(max, Math.max(min, value))
}