/**
 * 构建拆包规划器（Task 91）。
 *
 * 为多页应用（MPA）生成 manualChunks 配置，按页面拆分公共业务 chunk：
 * - vendorRules：全局 vendor 规则（Element Plus、Vue 运行时等），所有入口共享；
 * - perEntryRules：按入口隔离的页面私有 chunk（匹配需同时给出 entryName，
 *   未匹配入口的模块不会被误拆到其他页面 chunk）；
 * - 同名 chunk 的规则自动合并去重；未匹配模块返回 undefined，交由 Vite
 *   默认拆包逻辑处理，不强制拆包。
 *
 * 有界配置：maxRules 限制 vendor 规则数量（超限拒绝计数，规则不生效）；
 * maxEntries 限制登记的入口数量（超出部分连同其 per-entry 规则一并跳过）。
 * 校验失败（空 chunk 名、空 patterns、非法上限）fail-fast 抛错且零状态变更；
 * 规则读取抛错（依赖故障）时调用失败，规划状态不被污染，恢复后可继续使用。
 */
export interface ChunkRule {
  /** chunk 名，不能为空 */
  chunk: string
  /** 匹配模块 id 的字符串 pattern 列表，不能为空 */
  patterns: string[]
}

export interface EntryChunkRule extends ChunkRule {
  /** 关联的入口名，不能为空 */
  entry: string
}

export interface ChunkPlannerOptions {
  /** 页面入口列表；超过 maxEntries 的部分被跳过 */
  entries: string[]
  /** 全局 vendor 拆包规则；数量超过 maxRules 的部分被拒绝 */
  vendorRules?: ChunkRule[]
  /** 按入口隔离的页面 chunk 规则 */
  perEntryRules?: EntryChunkRule[]
  /** vendor 规则数量上限，必须为正数，默认 100 */
  maxRules?: number
  /** 登记的入口数量上限，必须为正数，默认 100 */
  maxEntries?: number
}

export interface ChunkPlan {
  entry: string
  chunks: string[]
}

export interface ChunkPlannerStats {
  entryCount: number
  chunkCount: number
  sharedChunkCount: number
  unmatchedCount: number
  rejectedCount: number
}

export interface ChunkPlanner {
  /** 分配模块到 chunk；未匹配返回 undefined（交给 Vite 默认拆包） */
  assign: (moduleId: string, entryName?: string) => string | undefined
  /** 生成 manualChunks 配置对象（chunk 名 → patterns） */
  manualChunksConfig: () => Record<string, string[]>
  /** 每个入口实际包含的 chunk 清单（公共 vendor + 页面私有） */
  planByEntry: () => ChunkPlan[]
  stats: () => ChunkPlannerStats
}

export function createChunkPlanner(options: ChunkPlannerOptions): ChunkPlanner {
  if (!Array.isArray(options.entries)) {
    throw new Error('entries 必须是数组')
  }
  const maxRules = options.maxRules ?? 100
  const maxEntries = options.maxEntries ?? 100
  if (!(maxRules > 0)) {
    throw new Error('maxRules 必须为正数: ' + maxRules)
  }
  if (!(maxEntries > 0)) {
    throw new Error('maxEntries 必须为正数: ' + maxEntries)
  }

  const entries = options.entries.slice(0, maxEntries)
  const entrySet = new Set(entries)
  const vendorRules: Array<{ chunk: string; patterns: string[] }> = []
  const perEntryRulesByEntry = new Map<string, Array<{ chunk: string; patterns: string[] }>>()
  const chunkNames: string[] = []
  let rejectedCount = 0
  let unmatchedCount = 0

  function validateRule(rule: ChunkRule) {
    if (typeof rule.chunk !== 'string' || rule.chunk.length === 0) {
      throw new Error('chunk 名不能为空')
    }
    if (!Array.isArray(rule.patterns) || rule.patterns.length === 0) {
      throw new Error('patterns 必须是非空数组')
    }
  }

  function mergePatterns(target: string[] | undefined, patterns: string[]): string[] {
    const result = target ? [...target] : []
    for (const pattern of patterns) {
      if (!result.includes(pattern)) result.push(pattern)
    }
    return result
  }

  function addVendorRule(rule: ChunkRule) {
    validateRule(rule)
    if (vendorRules.length >= maxRules) {
      rejectedCount += 1
      return
    }
    const existing = vendorRules.find((item) => item.chunk === rule.chunk)
    if (existing) {
      existing.patterns = mergePatterns(existing.patterns, rule.patterns)
    } else {
      vendorRules.push({ chunk: rule.chunk, patterns: [...rule.patterns] })
      chunkNames.push(rule.chunk)
    }
  }

  function addPerEntryRule(rule: EntryChunkRule) {
    if (typeof rule.entry !== 'string' || rule.entry.length === 0) {
      throw new Error('entry 名不能为空')
    }
    validateRule(rule)
    if (!entrySet.has(rule.entry)) return
    const rules = perEntryRulesByEntry.get(rule.entry) ?? []
    const existing = rules.find((item) => item.chunk === rule.chunk)
    if (existing) {
      existing.patterns = mergePatterns(existing.patterns, rule.patterns)
    } else {
      rules.push({ chunk: rule.chunk, patterns: [...rule.patterns] })
      perEntryRulesByEntry.set(rule.entry, rules)
      chunkNames.push(rule.chunk)
    }
  }

  for (const rule of options.vendorRules ?? []) {
    addVendorRule(rule)
  }
  for (const rule of options.perEntryRules ?? []) {
    addPerEntryRule(rule)
  }

  function matches(patterns: string[], moduleId: string): boolean {
    for (const pattern of patterns) {
      if (moduleId.includes(pattern)) return true
    }
    return false
  }

  function assign(moduleId: string, entryName?: string): string | undefined {
    for (const rule of vendorRules) {
      if (matches(rule.patterns, moduleId)) return rule.chunk
    }
    if (entryName !== undefined) {
      const rules = perEntryRulesByEntry.get(entryName)
      if (rules) {
        for (const rule of rules) {
          if (matches(rule.patterns, moduleId)) return rule.chunk
        }
      }
    }
    unmatchedCount += 1
    return undefined
  }

  function manualChunksConfig(): Record<string, string[]> {
    const config: Record<string, string[]> = {}
    for (const rule of vendorRules) {
      config[rule.chunk] = mergePatterns(config[rule.chunk], rule.patterns).sort()
    }
    for (const rules of perEntryRulesByEntry.values()) {
      for (const rule of rules) {
        config[rule.chunk] = mergePatterns(config[rule.chunk], rule.patterns).sort()
      }
    }
    return config
  }

  function planByEntry(): ChunkPlan[] {
    const vendorNames = vendorRules.map((rule) => rule.chunk)
    return entries.map((entry) => ({
      entry,
      chunks: [...vendorNames, ...(perEntryRulesByEntry.get(entry)?.map((rule) => rule.chunk) ?? [])],
    }))
  }

  function stats(): ChunkPlannerStats {
    return {
      entryCount: entries.length,
      chunkCount: chunkNames.length,
      sharedChunkCount: vendorRules.length,
      unmatchedCount,
      rejectedCount,
    }
  }

  return { assign, manualChunksConfig, planByEntry, stats }
}