/**
 * HuggingChatExecutor — HuggingChat (huggingface.co/chat) Web Provider
 *
 * Routes chat requests through HuggingChat's SvelteKit-based API.
 * Requires a valid session cookie from huggingface.co/chat.
 *
 * API flow:
 *   1. POST /chat/conversation  { model } -> { conversationId }
 *   2. GET /chat/api/v2/conversations/{id} -> { rootMessageId }
 *   3. POST /chat/conversation/{id}  (multipart: data = JSON{inputs, id}, optional files)
 *      -> JSONL stream of MessageUpdate objects
 *
 * Streaming format (JSONL, not SSE):
 *   - { type: "stream", token: "..." }        -- text tokens (padded to 16 chars with \0)
 *   - { type: "status", status: "started" }   -- generation started
 *   - { type: "status", status: "keepAlive" } -- heartbeat
 *   - { type: "finalAnswer", text: "..." }    -- complete response
 *   - { type: "reasoning", subtype: "stream", token: "..." } -- thinking tokens
 *   - { type: "status", status: "error", message: "..." }    -- error
 */
import {
  BaseExecutor,
  mergeAbortSignals,
  mergeUpstreamExtraHeaders,
  type ExecuteInput,
} from "./base.ts";
import { FETCH_TIMEOUT_MS } from "../config/constants.ts";
import { buildErrorBody, sanitizeErrorMessage } from "../utils/error.ts";
import { normalizeSessionCookieHeader } from "@/lib/providers/webCookieAuth";
import { streamJsonlToOpenAi, readJsonlResponse } from "./huggingchat/jsonlStream.ts";

const HUGGINGFACE_BASE = "https://huggingface.co";
const CONVERSATION_URL = `${HUGGINGFACE_BASE}/chat/conversation`;
const API_CONVERSATIONS_URL = `${HUGGINGFACE_BASE}/chat/api/v2/conversations`;
const DEFAULT_COOKIE_NAME = "hf-chat";

const USER_AGENT =
  "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/149.0.0.0 Safari/537.36";

const DEFAULT_MODEL = "baidu/ERNIE-4.5-VL-424B-A47B-Base-PT";

// -- Helpers -----------------------------------------------------------------

function normalizeHuggingChatCookieHeader(apiKey: string): string {
  return normalizeSessionCookieHeader(apiKey, DEFAULT_COOKIE_NAME);
}

function isEncryptedCredentialBlob(value: unknown): boolean {
  return typeof value === "string" && value.trim().startsWith("enc:v1:");
}

function extractTextFromContent(content: unknown): string {
  if (typeof content === "string") return content.trim();
  if (!Array.isArray(content)) return "";

  return content
    .map((part: unknown) => {
      if (!part || typeof part !== "object") return "";
      const item = part as Record<string, unknown>;
      if (item.type === "text" && typeof item.text === "string") return item.text;
      if (item.type === "input_text" && typeof item.text === "string") return item.text;
      return "";
    })
    .filter((p: string) => p.trim().length > 0)
    .join("\n")
    .trim();
}

function buildConversationPrompt(messages: Array<Record<string, unknown>>): {
  inputs: string;
  systemPrompt: string | null;
} {
  const systemParts: string[] = [];
  const conversationParts: Array<{ role: string; content: string }> = [];

  for (const msg of messages) {
    const role = String(msg.role || "user");
    const text = extractTextFromContent(msg.content);
    if (!text) continue;

    if (role === "system" || role === "developer") {
      systemParts.push(text);
    } else if (role === "user" || role === "assistant") {
      conversationParts.push({ role, content: text });
    }
  }

  if (conversationParts.length === 0) {
    return { inputs: systemParts.join("\n\n"), systemPrompt: null };
  }

  if (conversationParts.length === 1 && conversationParts[0].role === "user") {
    return {
      inputs: conversationParts[0].content,
      systemPrompt: systemParts.length > 0 ? systemParts.join("\n\n") : null,
    };
  }

  const lines: string[] = [];
  for (const part of conversationParts) {
    const label = part.role === "user" ? "User" : "Assistant";
    lines.push(`${label}: ${part.content}`);
  }
  lines.push("Assistant:");

  return {
    inputs: lines.join("\n\n"),
    systemPrompt: systemParts.length > 0 ? systemParts.join("\n\n") : null,
  };
}

function estimateTokens(text: string): number {
  return Math.max(1, Math.ceil((text || "").length / 4));
}

function getLocalTimezone(): string {
  try {
    return Intl.DateTimeFormat().resolvedOptions().timeZone || "UTC";
  } catch {
    return "UTC";
  }
}

async function readUpstreamErrorDetails(response: Response): Promise<{
  message: string | null;
  details: unknown;
}> {
  const contentType = response.headers.get("content-type") || "";
  const text = await response.text().catch(() => "");
  if (!text) return { message: null, details: null };

  if (contentType.includes("json")) {
    try {
      const parsed = JSON.parse(text) as Record<string, unknown>;
      const message =
        typeof parsed.message === "string"
          ? parsed.message
          : typeof parsed.error === "string"
            ? parsed.error
            : parsed.error &&
                typeof parsed.error === "object" &&
                typeof (parsed.error as Record<string, unknown>).message === "string"
              ? String((parsed.error as Record<string, unknown>).message)
              : null;
      return { message: message ? sanitizeErrorMessage(message) : null, details: parsed };
    } catch {
      // Fall through to text handling below.
    }
  }

  return { message: sanitizeErrorMessage(text), details: { body: text } };
}

function unwrapSuperjsonPayload(value: unknown): unknown {
  if (!value || typeof value !== "object" || Array.isArray(value)) return value;
  const record = value as Record<string, unknown>;
  return record.json && typeof record.json === "object" ? record.json : value;
}

function extractInitialParentMessageId(value: unknown): string | null {
  const payload = unwrapSuperjsonPayload(value);
  if (!payload || typeof payload !== "object" || Array.isArray(payload)) return null;

  const record = payload as Record<string, unknown>;
  if (typeof record.rootMessageId === "string" && record.rootMessageId.trim()) {
    return record.rootMessageId;
  }

  const messages = Array.isArray(record.messages) ? record.messages : [];
  const lastMessage = messages.at(-1);
  if (lastMessage && typeof lastMessage === "object") {
    const id = (lastMessage as Record<string, unknown>).id;
    if (typeof id === "string" && id.trim()) return id;
  }

  return null;
}

async function fetchInitialParentMessageId(
  conversationId: string,
  headers: Record<string, string>,
  signal: AbortSignal
): Promise<string | null> {
  const res = await fetch(`${API_CONVERSATIONS_URL}/${conversationId}`, {
    method: "GET",
    headers,
    signal,
  });
  if (!res.ok) return null;

  const text = await res.text().catch(() => "");
  if (!text) return null;

  try {
    return extractInitialParentMessageId(JSON.parse(text));
  } catch {
    return null;
  }
}

function splitCombinedSetCookieHeader(header: string): string[] {
  return header
    .split(/,(?=\s*[^;,=\s]+=)/)
    .map((value) => value.trim())
    .filter(Boolean);
}

function getSetCookieHeaders(headers: Headers): string[] {
  const maybeGetSetCookie = (headers as Headers & { getSetCookie?: () => string[] }).getSetCookie;
  if (typeof maybeGetSetCookie === "function") {
    return maybeGetSetCookie.call(headers).filter(Boolean);
  }

  const combined = headers.get("set-cookie");
  return combined ? splitCombinedSetCookieHeader(combined) : [];
}

function parseSetCookiePair(setCookie: string): { name: string; value: string } | null {
  const pair = setCookie.split(";", 1)[0]?.trim() || "";
  const eq = pair.indexOf("=");
  if (eq <= 0) return null;
  return { name: pair.slice(0, eq).trim(), value: pair.slice(eq + 1) };
}

function mergeCookieHeaderWithSetCookie(cookieHeader: string, setCookieHeaders: string[]): string {
  const cookieMap = new Map<string, string>();

  for (const part of cookieHeader.split(";")) {
    const trimmed = part.trim();
    if (!trimmed) continue;
    const eq = trimmed.indexOf("=");
    if (eq <= 0) continue;
    cookieMap.set(trimmed.slice(0, eq).trim(), trimmed.slice(eq + 1));
  }

  for (const setCookie of setCookieHeaders) {
    const parsed = parseSetCookiePair(setCookie);
    if (!parsed || !parsed.value) continue;
    cookieMap.set(parsed.name, parsed.value);
  }

  return [...cookieMap.entries()].map(([name, value]) => `${name}=${value}`).join("; ");
}

// -- Executor ----------------------------------------------------------------

export class HuggingChatExecutor extends BaseExecutor {
  constructor() {
    super("huggingchat", { id: "huggingchat", baseUrl: HUGGINGFACE_BASE });
  }

  async execute(input: ExecuteInput): Promise<{
    response: Response;
    url: string;
    headers: Record<string, string>;
    transformedBody: unknown;
  }> {
    const { model, body, stream, credentials, signal, log, upstreamExtraHeaders } = input;
    const messages = (body as Record<string, unknown>).messages as
      Array<Record<string, unknown>> | undefined;

    if (!messages || !Array.isArray(messages) || messages.length === 0) {
      return {
        response: new Response(
          JSON.stringify({
            error: { message: "Missing or empty messages array", type: "invalid_request" },
          }),
          { status: 400, headers: { "Content-Type": "application/json" } }
        ),
        url: CONVERSATION_URL,
        headers: {},
        transformedBody: body,
      };
    }

    if (isEncryptedCredentialBlob(credentials.apiKey)) {
      return {
        response: new Response(
          JSON.stringify({
            error: {
              message:
                "HuggingChat credentials are encrypted but STORAGE_ENCRYPTION_KEY is not loaded. " +
                "Restore the encryption key or re-save the HuggingChat cookie.",
              type: "auth_error",
            },
          }),
          { status: 401, headers: { "Content-Type": "application/json" } }
        ),
        url: CONVERSATION_URL,
        headers: {},
        transformedBody: body,
      };
    }

    let cookieHeader = normalizeHuggingChatCookieHeader(credentials.apiKey || "");
    if (!cookieHeader) {
      return {
        response: new Response(
          JSON.stringify({
            error: {
              message:
                "HuggingChat requires a session cookie. Log in to huggingface.co/chat, " +
                "open DevTools > Application > Cookies, and copy the hf-chat cookie value.",
              type: "auth_error",
            },
          }),
          { status: 401, headers: { "Content-Type": "application/json" } }
        ),
        url: CONVERSATION_URL,
        headers: {},
        transformedBody: body,
      };
    }

    const resolvedModel = model || DEFAULT_MODEL;
    const { inputs, systemPrompt } = buildConversationPrompt(messages);

    if (!inputs.trim()) {
      return {
        response: new Response(
          JSON.stringify({
            error: { message: "Empty prompt after processing messages", type: "invalid_request" },
          }),
          { status: 400, headers: { "Content-Type": "application/json" } }
        ),
        url: CONVERSATION_URL,
        headers: {},
        transformedBody: body,
      };
    }

    const baseHeaders: Record<string, string> = {
      Cookie: cookieHeader,
      "User-Agent": USER_AGENT,
      Origin: HUGGINGFACE_BASE,
      Referer: `${HUGGINGFACE_BASE}/chat/`,
    };

    // -- Step 1: Create conversation ----------------------------------------
    const timeoutSignal = AbortSignal.timeout(FETCH_TIMEOUT_MS);
    const combinedSignal = signal ? mergeAbortSignals(signal, timeoutSignal) : timeoutSignal;

    let conversationId: string;
    try {
      const createBody: Record<string, unknown> = { model: resolvedModel };
      if (systemPrompt) createBody.preprompt = systemPrompt;

      const createRes = await fetch(CONVERSATION_URL, {
        method: "POST",
        headers: { ...baseHeaders, "Content-Type": "application/json" },
        body: JSON.stringify(createBody),
        signal: combinedSignal,
      });

      if (!createRes.ok) {
        const status = createRes.status;
        const upstreamError = await readUpstreamErrorDetails(createRes);
        let message = `HuggingChat conversation creation failed (HTTP ${status})`;
        if (status === 401 || status === 403) {
          message =
            "HuggingChat auth failed -- your hf-chat session cookie may be missing or expired. " +
            "Log in to huggingface.co/chat and re-paste your cookie.";
        } else if (status === 429) {
          message = "HuggingChat rate limited. Wait a moment and retry.";
        }
        if (upstreamError.message) {
          message = `${message}: ${upstreamError.message}`;
        }
        return {
          response: new Response(
            JSON.stringify(buildErrorBody(status, message, upstreamError.details)),
            { status, headers: { "Content-Type": "application/json" } }
          ),
          url: CONVERSATION_URL,
          headers: baseHeaders,
          transformedBody: body,
        };
      }

      const createData = (await createRes.json()) as Record<string, unknown>;
      conversationId = createData.conversationId as string;
      const createSetCookieHeaders = getSetCookieHeaders(createRes.headers);
      cookieHeader = mergeCookieHeaderWithSetCookie(cookieHeader, createSetCookieHeaders);
      baseHeaders.Cookie = cookieHeader;

      if (!conversationId) {
        return {
          response: new Response(
            JSON.stringify({
              error: {
                message: "HuggingChat did not return a conversationId",
                type: "upstream_error",
              },
            }),
            { status: 502, headers: { "Content-Type": "application/json" } }
          ),
          url: CONVERSATION_URL,
          headers: baseHeaders,
          transformedBody: body,
        };
      }
    } catch (err) {
      const message = err instanceof Error ? err.message : String(err);
      log?.error?.("HUGGINGCHAT", `Conversation creation failed: ${message}`);
      return {
        response: new Response(
          JSON.stringify({
            error: { message: `HuggingChat connection failed: ${message}`, type: "upstream_error" },
          }),
          { status: 502, headers: { "Content-Type": "application/json" } }
        ),
        url: CONVERSATION_URL,
        headers: baseHeaders,
        transformedBody: body,
      };
    }

    // -- Step 2: Send message -----------------------------------------------
    const parentMessageId = await fetchInitialParentMessageId(
      conversationId,
      baseHeaders,
      combinedSignal
    );
    if (!parentMessageId) {
      return {
        response: new Response(
          JSON.stringify({
            error: {
              message: "HuggingChat did not return an initial parent message id",
              type: "upstream_error",
            },
          }),
          { status: 502, headers: { "Content-Type": "application/json" } }
        ),
        url: `${API_CONVERSATIONS_URL}/${conversationId}`,
        headers: baseHeaders,
        transformedBody: body,
      };
    }

    const messageUrl = `${CONVERSATION_URL}/${conversationId}`;
    const formData = new FormData();
    const sendDataPayload: Record<string, unknown> = {
      inputs,
      is_retry: false,
      is_continue: false,
      generationId: crypto.randomUUID(),
      selectedMcpServerNames: [],
      selectedMcpServers: [],
      timezone: getLocalTimezone(),
      id: parentMessageId,
    };
    formData.append("data", JSON.stringify(sendDataPayload));

    mergeUpstreamExtraHeaders(baseHeaders, upstreamExtraHeaders);

    let upstreamResponse: Response;
    try {
      upstreamResponse = await fetch(messageUrl, {
        method: "POST",
        headers: baseHeaders,
        body: formData,
        signal: combinedSignal,
      });
    } catch (err) {
      const message = err instanceof Error ? err.message : String(err);
      log?.error?.("HUGGINGCHAT", `Message send failed: ${message}`);
      return {
        response: new Response(
          JSON.stringify({
            error: { message: `HuggingChat connection failed: ${message}`, type: "upstream_error" },
          }),
          { status: 502, headers: { "Content-Type": "application/json" } }
        ),
        url: messageUrl,
        headers: baseHeaders,
        transformedBody: sendDataPayload,
      };
    }

    if (!upstreamResponse.ok) {
      const status = upstreamResponse.status;
      const upstreamError = await readUpstreamErrorDetails(upstreamResponse);
      let message = `HuggingChat returned HTTP ${status}`;
      if (status === 401 || status === 403) {
        message = "HuggingChat auth failed -- session cookie may be expired.";
      } else if (status === 429) {
        message = "HuggingChat rate limited. Wait a moment and retry.";
      } else if (status === 404) {
        message = `HuggingChat model not found: ${resolvedModel}. Check the model ID.`;
      }
      if (upstreamError.message) {
        message = `${message}: ${upstreamError.message}`;
      }
      return {
        response: new Response(
          JSON.stringify(buildErrorBody(status, message, upstreamError.details)),
          { status, headers: { "Content-Type": "application/json" } }
        ),
        url: messageUrl,
        headers: baseHeaders,
        transformedBody: sendDataPayload,
      };
    }

    if (!upstreamResponse.body) {
      return {
        response: new Response(
          JSON.stringify({
            error: { message: "HuggingChat returned empty response body", type: "upstream_error" },
          }),
          { status: 502, headers: { "Content-Type": "application/json" } }
        ),
        url: messageUrl,
        headers: baseHeaders,
        transformedBody: sendDataPayload,
      };
    }

    // -- Step 3: Build response ---------------------------------------------
    const id = `chatcmpl-huggingchat-${crypto.randomUUID().slice(0, 12)}`;
    const created = Math.floor(Date.now() / 1000);

    if (stream) {
      const encoder = new TextEncoder();
      const jsonlStream = streamJsonlToOpenAi(
        upstreamResponse.body,
        resolvedModel,
        id,
        created,
        signal
      );

      const sseStream = new ReadableStream({
        async start(controller) {
          try {
            for await (const chunk of jsonlStream) {
              controller.enqueue(encoder.encode(chunk));
            }
          } catch (err) {
            log?.error?.("HUGGINGCHAT", `Stream error: ${err}`);
          } finally {
            controller.close();
          }
        },
      });

      return {
        response: new Response(sseStream, {
          status: 200,
          headers: {
            "Content-Type": "text/event-stream",
            "Cache-Control": "no-cache",
            "X-Accel-Buffering": "no",
          },
        }),
        url: messageUrl,
        headers: baseHeaders,
        transformedBody: sendDataPayload,
      };
    }

    const fullText = await readJsonlResponse(upstreamResponse.body, signal);
    const completionTokens = estimateTokens(fullText);

    return {
      response: new Response(
        JSON.stringify({
          id,
          object: "chat.completion",
          created,
          model: resolvedModel,
          choices: [
            {
              index: 0,
              message: { role: "assistant", content: fullText },
              finish_reason: "stop",
            },
          ],
          usage: {
            prompt_tokens: estimateTokens(inputs),
            completion_tokens: completionTokens,
            total_tokens: estimateTokens(inputs) + completionTokens,
          },
        }),
        { status: 200, headers: { "Content-Type": "application/json" } }
      ),
      url: messageUrl,
      headers: baseHeaders,
      transformedBody: sendDataPayload,
    };
  }
}