/**
 * Responses ⇄ Chat Completions 翻译层（纯函数 + SSE 状态机，零 IO）。
 *
 * 规格依据：codex rust-v0.155.1 的线协议（codex-api/src/common.rs、
 * codex-api/src/sse/responses.rs、protocol/src/models.rs）：
 * - 请求侧白名单式构建：store/include/reasoning/prompt_cache_key/text/client_metadata
 *   等 Chat 上游不认识的字段一律不发，宁可少发不发错。
 * - 响应侧只产 codex 实际消费的事件：output_item.done 是唯一驱动历史与工具执行的通道，
 *   function_call 的 arguments 必须整体出现在 done（0.155.1 忽略 arguments.delta），
 *   response.completed 的 response.id 必填，缺 usage 只影响统计不影响结束。
 * - tool_call_id 链路：Responses 的 call_id 原样作为 Chat 的 tool_calls[].id 与
 *   role:"tool" 消息的 tool_call_id，codex 侧不透明字符串原样回传。
 */

export type DiagnosticFn = (message: string) => void;

/** codex POST /v1/responses 的请求体（只声明翻译用得到的字段，其余按白名单丢弃） */
export interface ResponsesCreateParams {
  model?: unknown;
  instructions?: unknown;
  input?: unknown;
  tools?: unknown;
  tool_choice?: unknown;
  parallel_tool_calls?: unknown;
  max_output_tokens?: unknown;
  temperature?: unknown;
  top_p?: unknown;
  stream?: unknown;
  [key: string]: unknown;
}

export interface ChatToolCall {
  id: string;
  type: 'function';
  function: { name: string; arguments: string };
}

export interface ChatMessage {
  role: 'developer' | 'system' | 'user' | 'assistant' | 'tool';
  content?: unknown;
  tool_calls?: ChatToolCall[];
  tool_call_id?: string;
  name?: string;
}

export interface ChatCompletionRequest {
  model: string;
  messages: ChatMessage[];
  stream: boolean;
  stream_options?: { include_usage: boolean };
  tools?: Array<{ type: 'function'; function: { name: string; description?: string; parameters?: unknown } }>;
  tool_choice?: 'auto' | 'none' | 'required' | { type: 'function'; function: { name: string } };
  parallel_tool_calls?: boolean;
  max_tokens?: number;
  temperature?: number;
  top_p?: number;
}

interface ChatToolCallDelta {
  index?: number;
  id?: string;
  function?: { name?: string; arguments?: string };
}

interface ChatChunkChoice {
  delta?: { content?: string | null; reasoning_content?: string | null; tool_calls?: ChatToolCallDelta[] };
  finish_reason?: string | null;
}

interface ChatChunk {
  choices?: ChatChunkChoice[];
  usage?: {
    prompt_tokens?: number;
    completion_tokens?: number;
    total_tokens?: number;
  } | null;
}

/** 翻译过程中丢弃的非空内容计数，进诊断，绝不静默有损 */
export interface TranslateDiagnostics {
  droppedInputItems: Map<string, number>;
  droppedContentParts: Map<string, number>;
  droppedTools: number;
}

function emptyDiagnostics(): TranslateDiagnostics {
  return { droppedInputItems: new Map(), droppedContentParts: new Map(), droppedTools: 0 };
}

function bump(map: Map<string, number>, key: string): void {
  map.set(key, (map.get(key) ?? 0) + 1);
}

function diagnosticsMessage(diagnostics: TranslateDiagnostics): string {
  const parts: string[] = [];
  for (const [key, count] of diagnostics.droppedInputItems) parts.push(`input.${key}×${count}`);
  for (const [key, count] of diagnostics.droppedContentParts) parts.push(`content.${key}×${count}`);
  if (diagnostics.droppedTools > 0) parts.push(`tools×${diagnostics.droppedTools}`);
  return parts.join(', ');
}

function asRecord(value: unknown): Record<string, unknown> | null {
  return value !== null && typeof value === 'object' && !Array.isArray(value)
    ? (value as Record<string, unknown>)
    : null;
}

function asString(value: unknown): string | null {
  return typeof value === 'string' ? value : null;
}

/** Responses 的 input_image → Chat image_url */
function imageContentPart(part: Record<string, unknown>): ChatContentPart | null {
  const url = asString(part.image_url) ?? asString(asRecord(part.image_url)?.url);
  return url ? { type: 'image_url', image_url: { url } } : null;
}

type ChatContentPart = { type: 'text'; text: string } | { type: 'image_url'; image_url: { url: string } };

/** Responses message 的 content 数组 → Chat content（文本/图片；单文本压成字符串兼容性最好） */
function translateMessageContent(parts: unknown[], diagnostics: TranslateDiagnostics): string | ChatContentPart[] {
  const translated: ChatContentPart[] = [];
  for (const part of parts) {
    const record = asRecord(part);
    const type = asString(record?.type);
    if (type === 'input_text' || type === 'output_text') {
      const text = asString(record?.text) ?? '';
      translated.push({ type: 'text', text });
    } else if (type === 'input_image') {
      const image = imageContentPart(record ?? {});
      if (image) translated.push(image);
      else bump(diagnostics.droppedContentParts, 'input_image');
    } else if (type !== null) {
      bump(diagnostics.droppedContentParts, type ?? 'unknown');
    }
  }
  const textsOnly = translated.every((part) => part.type === 'text');
  if (textsOnly && translated.length <= 1) return (translated[0] as { text: string } | undefined)?.text ?? '';
  return translated;
}

/** function_call_output.output：字符串或结构化数组，折叠成 Chat tool 消息的文本 content */
function translateOutputValue(value: unknown, diagnostics: TranslateDiagnostics): string {
  if (typeof value === 'string') return value;
  if (Array.isArray(value)) {
    const texts: string[] = [];
    for (const part of value) {
      const record = asRecord(part);
      const type = asString(record?.type);
      if (type === 'input_text' || type === 'output_text' || type === 'text') {
        texts.push(asString(record?.text) ?? '');
      } else {
        bump(diagnostics.droppedContentParts, type ?? 'unknown');
      }
    }
    return texts.join('\n');
  }
  if (value === null || value === undefined) return '';
  return String(value);
}

/**
 * Responses 请求体 → Chat Completions 请求体。
 * stream 透传；stream:true 时补 stream_options.include_usage（不支持的端点会忽略）。
 */
export function responsesToChatRequest(
  req: ResponsesCreateParams,
  onDiagnostic?: DiagnosticFn,
): ChatCompletionRequest {
  const diagnostics = emptyDiagnostics();
  const messages: ChatMessage[] = [];

  const instructions = asString(req.instructions);
  if (instructions) messages.push({ role: 'developer', content: instructions });

  const input = req.input;
  if (typeof input === 'string') {
    messages.push({ role: 'user', content: input });
  } else if (Array.isArray(input)) {
    for (const raw of input) {
      const item = asRecord(raw);
      if (!item) continue;
      const type = asString(item.type);
      if (type === null || type === 'message') {
        const role = asString(item.role) ?? 'user';
        const content = Array.isArray(item.content)
          ? translateMessageContent(item.content, diagnostics)
          : asString(item.content) ?? '';
        messages.push({ role: role === 'developer' ? 'developer' : role as ChatMessage['role'], content });
        continue;
      }
      if (type === 'function_call' || type === 'custom_tool_call') {
        const callId = asString(item.call_id) ?? '';
        const name = asString(item.name) ?? '';
        const args = type === 'custom_tool_call'
          ? asString(item.input) ?? JSON.stringify(item.input ?? null)
          : typeof item.arguments === 'string' ? item.arguments : JSON.stringify(item.arguments ?? null);
        messages.push({
          role: 'assistant',
          content: null,
          tool_calls: [{ id: callId, type: 'function', function: { name, arguments: args } }],
        });
        continue;
      }
      if (type === 'function_call_output' || type === 'custom_tool_call_output') {
        messages.push({
          role: 'tool',
          tool_call_id: asString(item.call_id) ?? '',
          content: translateOutputValue(item.output, diagnostics),
        });
        continue;
      }
      // reasoning / local_shell_call / web_search_call / item_reference 等对 Chat 上游无意义
      bump(diagnostics.droppedInputItems, type ?? 'unknown');
    }
  }

  const chat: ChatCompletionRequest = {
    model: asString(req.model) ?? '',
    messages,
    stream: req.stream === true,
  };
  if (chat.stream) chat.stream_options = { include_usage: true };

  const tools = Array.isArray(req.tools) ? req.tools : [];
  const chatTools: ChatCompletionRequest['tools'] = [];
  for (const raw of tools) {
    const tool = asRecord(raw);
    if (asString(tool?.type) !== 'function') {
      diagnostics.droppedTools += 1;
      continue;
    }
    const description = asString(tool?.description);
    chatTools.push({
      type: 'function',
      function: {
        name: asString(tool?.name) ?? '',
        ...(description ? { description } : {}),
        ...(tool?.parameters !== undefined ? { parameters: tool?.parameters } : {}),
      },
    });
  }
  if (chatTools.length) chat.tools = chatTools;

  const toolChoice = req.tool_choice;
  if (toolChoice === 'auto' || toolChoice === 'none' || toolChoice === 'required') {
    chat.tool_choice = toolChoice;
  } else if (asString(asRecord(toolChoice)?.type) === 'function' && asRecord(toolChoice)?.name) {
    chat.tool_choice = { type: 'function', function: { name: asString(asRecord(toolChoice)?.name) ?? '' } };
  } else if (toolChoice !== undefined && toolChoice !== null) {
    bump(diagnostics.droppedInputItems, `tool_choice:${typeof toolChoice}`);
  }

  if (typeof req.parallel_tool_calls === 'boolean') chat.parallel_tool_calls = req.parallel_tool_calls;
  if (typeof req.max_output_tokens === 'number') chat.max_tokens = req.max_output_tokens;
  if (typeof req.temperature === 'number') chat.temperature = req.temperature;
  if (typeof req.top_p === 'number') chat.top_p = req.top_p;

  const summary = diagnosticsMessage(diagnostics);
  if (summary && onDiagnostic) onDiagnostic(`有损转换丢弃：${summary}`);
  return chat;
}

/** Chat 非流式响应 → Responses 形状（防御路径：codex 恒为 stream:true） */
export function chatResponseToResponses(chat: Record<string, unknown>, responseId: string): Record<string, unknown> {
  const diagnostics = emptyDiagnostics();
  const choices = Array.isArray(chat.choices) ? chat.choices : [];
  const choice = asRecord(choices[0]) ?? {};
  const message = asRecord(choice.message) ?? {};
  const finishReason = asString(choice.finish_reason);

  const output: Array<Record<string, unknown>> = [];
  const reasoning = asString(message.reasoning_content) ?? asString(message.reasoning);
  if (reasoning) {
    output.push({
      type: 'reasoning',
      id: 'rs_1',
      summary: [{ type: 'summary_text', text: reasoning }],
    });
  }
  const content = asString(message.content);
  if (content) {
    output.push({
      type: 'message',
      id: 'msg_1',
      role: 'assistant',
      status: 'completed',
      content: [{ type: 'output_text', text: content }],
    });
  }
  const toolCalls = Array.isArray(message.tool_calls) ? message.tool_calls : [];
  let callIndex = 0;
  for (const raw of toolCalls) {
    const call = asRecord(raw);
    const fn = asRecord(call?.function);
    callIndex += 1;
    output.push({
      type: 'function_call',
      id: `fc_${callIndex}`,
      call_id: asString(call?.id) ?? `call_${callIndex}`,
      name: asString(fn?.name) ?? '',
      arguments: asString(fn?.arguments) ?? '',
      status: 'completed',
    });
  }
  if (!reasoning && !content && toolCalls.length === 0) {
    bump(diagnostics.droppedInputItems, 'empty_choice');
  }

  const usage = asRecord(chat.usage);
  const promptTokens = typeof usage?.prompt_tokens === 'number' ? usage.prompt_tokens : 0;
  const completionTokens = typeof usage?.completion_tokens === 'number' ? usage.completion_tokens : 0;
  const totalTokens = typeof usage?.total_tokens === 'number' ? usage.total_tokens : promptTokens + completionTokens;

  const incomplete = finishReason === 'length';
  return {
    id: responseId,
    object: 'response',
    status: incomplete ? 'incomplete' : 'completed',
    ...(incomplete ? { incomplete_details: { reason: 'max_output_tokens' } } : {}),
    output,
    usage: {
      input_tokens: promptTokens,
      input_tokens_details: { cached_tokens: 0 },
      output_tokens: completionTokens,
      output_tokens_details: { reasoning_tokens: 0 },
      total_tokens: totalTokens,
    },
    parallel_tool_calls: typeof chat.parallel_tool_calls === 'boolean' ? chat.parallel_tool_calls : undefined,
  };
}

export type BridgeSseFrame = string;

interface OpenToolCall {
  callId: string | null;
  name: string;
  arguments: string;
  itemId: string;
}

function randomId(): string {
  return Math.random().toString(36).slice(2, 10) + Date.now().toString(36).slice(-6);
}

function sseFrame(type: string, data: Record<string, unknown>): string {
  return `event: ${type}\ndata: ${JSON.stringify({ type, ...data })}\n\n`;
}

/**
 * 上游 Chat SSE → codex Responses SSE 的流式状态机。
 * push() 吃任意分包的文本（内部按行缓冲），finish()/fail() 收尾且幂等。
 * 一个响应内文本/推理/工具调用的 item 顺序：按上游到达顺序开闭，工具调用按 index 归拢后
 * 在 finish（或出现更大 index）时补发完整 done —— arguments 必须整体出现。
 */
export class ChatSseTranslator {
  readonly #responseId: string;
  readonly #onDiagnostic?: DiagnosticFn;
  #buffer = '';
  #itemSeq = 0;
  #closed = false;
  #textState: { itemId: string; text: string } | null = null;
  #reasoningState: { itemId: string; text: string } | null = null;
  /** index → 归拢中的工具调用；出现更大 index 时先收口前面的 */
  #toolCalls = new Map<number, OpenToolCall>();
  #toolCallOrder: number[] = [];
  #toolCallsDone = false;
  #finishReason: string | null = null;
  #usage: { input_tokens: number; output_tokens: number; total_tokens: number } | null = null;
  #upstreamBytes = 0;
  #emittedEvents = 0;

  constructor(onDiagnostic?: DiagnosticFn) {
    this.#onDiagnostic = onDiagnostic;
    this.#responseId = `resp_${randomId()}`;
  }

  get responseId(): string {
    return this.#responseId;
  }

  get upstreamBytes(): number {
    return this.#upstreamBytes;
  }

  get emittedEvents(): number {
    return this.#emittedEvents;
  }

  #frame(type: string, data: Record<string, unknown>): string {
    this.#emittedEvents += 1;
    return sseFrame(type, data);
  }

  #nextItemId(prefix: string): string {
    this.#itemSeq += 1;
    return `${prefix}_${this.#itemSeq}`;
  }

  /** 先建 SSE：不等上游响应头就发 created + in_progress，防单槽端点慢 prefill 掐线 */
  begin(): string[] {
    if (this.#closed) return [];
    return [
      this.#frame('response.created', { response: { id: this.#responseId } }),
      this.#frame('response.in_progress', { response: { id: this.#responseId } }),
    ];
  }

  /** 关闭当前打开的文本/推理 item，产出 done 帧 */
  #closeText(): string[] {
    if (!this.#textState) return [];
    const { itemId, text } = this.#textState;
    this.#textState = null;
    return [
      this.#frame('response.output_item.done', {
        item: {
          type: 'message',
          id: itemId,
          role: 'assistant',
          status: 'completed',
          content: [{ type: 'output_text', text }],
        },
      }),
    ];
  }

  #closeReasoning(): string[] {
    if (!this.#reasoningState) return [];
    const { itemId, text } = this.#reasoningState;
    this.#reasoningState = null;
    return [
      this.#frame('response.output_item.done', {
        item: {
          type: 'reasoning',
          id: itemId,
          summary: [{ type: 'summary_text', text }],
        },
      }),
    ];
  }

  /** 收口所有归拢中的工具调用（按 index 序），产出完整 function_call done 帧 */
  #closeToolCalls(): string[] {
    if (this.#toolCallsDone) return [];
    this.#toolCallsDone = true;
    const frames: string[] = [];
    for (const index of this.#toolCallOrder) {
      const call = this.#toolCalls.get(index);
      if (!call) continue;
      frames.push(
        this.#frame('response.output_item.done', {
          item: {
            type: 'function_call',
            id: call.itemId,
            call_id: call.callId ?? `call_${index}`,
            name: call.name,
            arguments: call.arguments,
            status: 'completed',
          },
        }),
      );
    }
    return frames;
  }

  push(chunk: string): string[] {
    if (this.#closed) return [];
    this.#upstreamBytes += Buffer.byteLength(chunk);
    this.#buffer += chunk;
    const frames: string[] = [];
    let newlineIndex = this.#buffer.indexOf('\n');
    while (newlineIndex >= 0) {
      const line = this.#buffer.slice(0, newlineIndex).replace(/\r$/, '');
      this.#buffer = this.#buffer.slice(newlineIndex + 1);
      const payload = this.#dataPayload(line);
      if (payload) frames.push(...this.#handleData(payload));
      newlineIndex = this.#buffer.indexOf('\n');
    }
    return frames;
  }

  /** 提取 SSE data: 行的载荷；[DONE]/注释行/空行返回 null */
  #dataPayload(line: string): string | null {
    if (!line.startsWith('data:')) return null;
    const payload = line.slice(5).trim();
    if (!payload || payload === '[DONE]') return null;
    return payload;
  }

  #handleData(payload: string): string[] {
    let chunk: ChatChunk;
    try {
      chunk = JSON.parse(payload) as ChatChunk;
    } catch {
      // 坏 JSON 跳过不杀流
      this.#onDiagnostic?.('上游 SSE 出现无法解析的 JSON 分片，已跳过');
      return [];
    }
    const frames: string[] = [];
    if (chunk.usage && typeof chunk.usage === 'object') {
      const promptTokens = typeof chunk.usage.prompt_tokens === 'number' ? chunk.usage.prompt_tokens : 0;
      const completionTokens = typeof chunk.usage.completion_tokens === 'number' ? chunk.usage.completion_tokens : 0;
      const totalTokens = typeof chunk.usage.total_tokens === 'number'
        ? chunk.usage.total_tokens
        : promptTokens + completionTokens;
      this.#usage = { input_tokens: promptTokens, output_tokens: completionTokens, total_tokens: totalTokens };
    }

    const choice = chunk.choices?.[0];
    if (!choice) return frames;

    if (choice.finish_reason) this.#finishReason = choice.finish_reason;
    const delta = choice.delta;

    if (delta?.tool_calls?.length) {
      // 工具调用开跑：先收口打开的文本/推理 item
      frames.push(...this.#closeText(), ...this.#closeReasoning());
      for (const callDelta of delta.tool_calls) {
        const index = typeof callDelta.index === 'number' ? callDelta.index : 0;
        let call = this.#toolCalls.get(index);
        if (!call) {
          // 出现新 index：说明更小的 index 已收口完成
          frames.push(...this.#closeEarlierToolCalls(index));
          call = { callId: null, name: '', arguments: '', itemId: this.#nextItemId('fc') };
          this.#toolCalls.set(index, call);
          this.#toolCallOrder.push(index);
        }
        if (callDelta.id) call.callId = callDelta.id;
        if (callDelta.function?.name) call.name += callDelta.function.name;
        if (callDelta.function?.arguments) call.arguments += callDelta.function.arguments;
      }
    }

    if (typeof delta?.reasoning_content === 'string' && delta.reasoning_content.length > 0) {
      if (this.#textState) frames.push(...this.#closeText());
      if (!this.#reasoningState) {
        this.#reasoningState = { itemId: this.#nextItemId('rs'), text: '' };
        frames.push(
          this.#frame('response.output_item.added', {
            item: { type: 'reasoning', id: this.#reasoningState.itemId, summary: [] },
          }),
        );
      }
      this.#reasoningState.text += delta.reasoning_content;
      frames.push(
        this.#frame('response.reasoning_summary_text.delta', {
          delta: delta.reasoning_content,
          summary_index: 0,
          item_id: this.#reasoningState.itemId,
        }),
      );
    }

    if (typeof delta?.content === 'string' && delta.content.length > 0) {
      if (this.#reasoningState) frames.push(...this.#closeReasoning());
      if (!this.#textState) {
        this.#textState = { itemId: this.#nextItemId('msg'), text: '' };
        frames.push(
          this.#frame('response.output_item.added', {
            item: { type: 'message', id: this.#textState.itemId, role: 'assistant', content: [] },
          }),
        );
      }
      this.#textState.text += delta.content;
      frames.push(this.#frame('response.output_text.delta', { delta: delta.content, item_id: this.#textState.itemId }));
    }

    return frames;
  }

  /** 出现 index N 时收口所有 < N 的工具调用 */
  #closeEarlierToolCalls(index: number): string[] {
    const frames: string[] = [];
    for (const earlier of this.#toolCallOrder) {
      if (earlier >= index) break;
      const call = this.#toolCalls.get(earlier);
      if (!call) continue;
      frames.push(
        this.#frame('response.output_item.done', {
          item: {
            type: 'function_call',
            id: call.itemId,
            call_id: call.callId ?? `call_${earlier}`,
            name: call.name,
            arguments: call.arguments,
            status: 'completed',
          },
        }),
      );
      this.#toolCalls.delete(earlier);
    }
    return frames;
  }

  /** [DONE]/上游结束：收口全部 item 并补 response.completed。幂等 */
  finish(): string[] {
    if (this.#closed) return [];
    this.#closed = true;
    const frames: string[] = [
      ...this.#closeReasoning(),
      ...this.#closeText(),
      ...this.#closeToolCalls(),
    ];
    const incomplete = this.#finishReason === 'length';
    frames.push(
      this.#frame('response.completed', {
        response: {
          id: this.#responseId,
          status: incomplete ? 'incomplete' : 'completed',
          ...(incomplete ? { incomplete_details: { reason: 'max_output_tokens' } } : {}),
          ...(this.#usage ? { usage: {
            input_tokens: this.#usage.input_tokens,
            input_tokens_details: { cached_tokens: 0 },
            output_tokens: this.#usage.output_tokens,
            output_tokens_details: { reasoning_tokens: 0 },
            total_tokens: this.#usage.total_tokens,
          } } : {}),
        },
      }),
    );
    return frames;
  }

  /** 上游失败：补 response.failed 让 codex 走错误映射。幂等 */
  fail(message: string): string[] {
    if (this.#closed) return [];
    this.#closed = true;
    return [
      this.#frame('response.failed', {
        response: {
          id: this.#responseId,
          error: { code: 'upstream_error', message },
        },
      }),
    ];
  }
}