/**
 * GeminiWebExecutor — Gemini Web Session Provider
 *
 * Routes requests through Google Gemini's web interface using browser
 * cookies + Playwright automation. Translates between OpenAI chat
 * completions format and Gemini's web UI.
 *
 * Auth: Cookie-based (__Secure-1PSID + __Secure-1PSIDTS from gemini.google.com)
 * Method: Playwright browser automation
 *
 * Note: Streaming is pseudo-streaming — waits for full Gemini response then
 * sends as single SSE chunk. Gemini's StreamGenerate endpoint returns complete
 * responses, not chunked streams.
 */

import { BaseExecutor, type ExecuteInput } from "./base.ts";
import { sanitizeErrorMessage } from "../utils/error.ts";

// ─── Constants ──────────────────────────────────────────────────────────────

const GEMINI_URL = "https://gemini.google.com/app";

/**
 * Whether an error came from Playwright failing to launch because the browser binary is not
 * installed (`chromium.launch: Executable doesn't exist at ...`). This is a host/config
 * problem, not a transient upstream fault, so the executor must NOT surface it as a retryable
 * 500 (which marks the account unavailable and loops / trips the provider breaker). See #3516.
 */
export function isMissingBrowserExecutable(message: string): boolean {
  if (!message) return false;
  return /executable doesn't exist|executablenotfound|playwright install|chromium.*download/i.test(
    message
  );
}
const GEMINI_USER_AGENT =
  "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/149.0.0.0 Safari/537.36";

// ─── Types ──────────────────────────────────────────────────────────────────

interface GeminiMessage {
  role: string;
  content: string;
}

interface GeminiRequestBody {
  messages: GeminiMessage[];
  model?: string;
  stream?: boolean;
}

// ─── Helpers ────────────────────────────────────────────────────────────────

function formatChatCompletion(content: string, model: string, finishReason = "stop") {
  return {
    id: `chatcmpl-${Date.now()}`,
    object: "chat.completion",
    created: Math.floor(Date.now() / 1000),
    model,
    choices: [{ index: 0, message: { role: "assistant", content }, finish_reason: finishReason }],
    usage: { prompt_tokens: 0, completion_tokens: 0, total_tokens: 0 },
  };
}

function formatStreamChunk(content: string, model: string, finishReason: string | null = null) {
  return {
    id: `chatcmpl-${Date.now()}`,
    object: "chat.completion.chunk",
    created: Math.floor(Date.now() / 1000),
    model,
    choices: [{ index: 0, delta: content ? { content } : {}, finish_reason: finishReason }],
  };
}

/**
 * Parse cookie string, stripping attributes (Path, Domain, Expires, etc.)
 * Input: full browser cookie string or just "name=value; name2=value2"
 * Output: array of { name, value } pairs
 */
function parseCookies(raw: string): Array<{ name: string; value: string }> {
  return raw
    .split(";")
    .map((part) => part.trim())
    .filter(Boolean)
    .map((part) => {
      const eqIdx = part.indexOf("=");
      if (eqIdx === -1) return null;
      const name = part.substring(0, eqIdx).trim();
      const value = part.substring(eqIdx + 1).trim();
      // Skip cookie attributes that aren't name=value pairs
      if (!name || !value) return null;
      const lowerName = name.toLowerCase();
      if (
        ["path", "domain", "expires", "max-age", "secure", "httponly", "samesite"].includes(
          lowerName
        )
      ) {
        return null;
      }
      return { name, value };
    })
    .filter(Boolean) as Array<{ name: string; value: string }>;
}

/**
 * Parse Gemini StreamGenerate response text.
 *
 * Response format:
 *   )]}'
 *   <length>
 *   [["wrb.fr", null, "<JSON string>"]]
 *   <length>
 *   [["wrb.fr", null, "<JSON string>"]]
 *
 * The JSON string contains nested array: inner[4][0][1] = ["text chunks"].
 * We concatenate text from every wrb.fr line because Gemini can split one
 * assistant answer across multiple StreamGenerate chunks.
 */
export function parseStreamResponse(raw: string): string {
  const lines = raw.split("\n");
  const textChunks: string[] = [];

  for (const rawLine of lines) {
    const line = rawLine.trim();
    if (!line || line === ")]}'" || /^\d+$/.test(line)) continue;
    if (!line.includes("wrb.fr")) continue;
    try {
      const arr = JSON.parse(line);
      if (!Array.isArray(arr) || !Array.isArray(arr[0]) || arr[0][0] !== "wrb.fr") continue;
      const payload = arr[0]?.[2];
      if (typeof payload !== "string") continue;
      const inner = JSON.parse(payload);
      // Defensive: check each level before accessing
      const responseArray = inner?.[4]?.[0]?.[1];
      if (!Array.isArray(responseArray)) continue;
      const text = responseArray.filter((c: unknown) => typeof c === "string").join("");
      if (text) textChunks.push(text);
    } catch {
      // Skip unparseable lines
    }
  }
  return textChunks.join("");
}

function readCredentialString(value: unknown): string {
  if (typeof value !== "string") return "";
  const trimmed = value.trim();
  return trimmed.length > 0 ? trimmed : "";
}

function readProviderSpecificString(
  providerSpecificData: unknown,
  keys: readonly string[]
): string {
  if (
    !providerSpecificData ||
    typeof providerSpecificData !== "object" ||
    Array.isArray(providerSpecificData)
  ) {
    return "";
  }
  const data = providerSpecificData as Record<string, unknown>;
  for (const key of keys) {
    const value = readCredentialString(data[key]);
    if (value) return value;
  }
  return "";
}

function normalizeGeminiCookieInput(raw: string, cookieName = "__Secure-1PSID"): string {
  const trimmed = raw.trim();
  if (!trimmed) return "";
  return trimmed.includes("=") ? trimmed : `${cookieName}=${trimmed}`;
}

function resolveGeminiWebCookie(credentials: ExecuteInput["credentials"]): string {
  const directCookie =
    readCredentialString(credentials?.apiKey) ||
    readCredentialString((credentials as Record<string, unknown> | undefined)?.cookie);
  if (directCookie) return normalizeGeminiCookieInput(directCookie);

  const providerSpecificData = credentials?.providerSpecificData;
  const cookie = readProviderSpecificString(providerSpecificData, ["cookie"]);
  if (cookie) return normalizeGeminiCookieInput(cookie);

  const psid = readProviderSpecificString(providerSpecificData, ["__Secure-1PSID"]);
  const psidts = readProviderSpecificString(providerSpecificData, ["__Secure-1PSIDTS"]);
  return [
    psid ? normalizeGeminiCookieInput(psid, "__Secure-1PSID") : "",
    psidts ? normalizeGeminiCookieInput(psidts, "__Secure-1PSIDTS") : "",
  ]
    .filter(Boolean)
    .join("; ");
}

// ─── Executor ───────────────────────────────────────────────────────────────

export class GeminiWebExecutor extends BaseExecutor {
  constructor() {
    super("gemini-web", { id: "gemini-web", baseUrl: GEMINI_URL });
  }

  async execute(input: ExecuteInput) {
    const { model, body, stream, credentials, signal } = input;
    const requestBody = body as GeminiRequestBody;

    const cookie = resolveGeminiWebCookie(credentials);
    if (!cookie) {
      return {
        response: new Response(JSON.stringify({ error: "Missing Gemini cookies" }), {
          status: 401,
          headers: { "Content-Type": "application/json" },
        }),
        url: GEMINI_URL,
        headers: {},
        transformedBody: body,
      };
    }

    const messages = requestBody.messages || [];
    const lastUserMsg = messages.filter((m) => m.role === "user").pop();
    const prompt = lastUserMsg?.content || "";

    if (!prompt) {
      return {
        response: new Response(JSON.stringify({ error: "No user message found" }), {
          status: 400,
          headers: { "Content-Type": "application/json" },
        }),
        url: GEMINI_URL,
        headers: {},
        transformedBody: body,
      };
    }

    let browser: any = null;
    let abortBrowser: (() => void) | null = null;
    try {
      if (signal?.aborted) {
        throw signal.reason instanceof Error ? signal.reason : new Error("Request aborted");
      }
      const { chromium } = await import("playwright");
      browser = await chromium.launch({ headless: true });
      abortBrowser = () => {
        void browser?.close().catch(() => {});
      };
      signal?.addEventListener("abort", abortBrowser, { once: true });

      const context = await browser.newContext({ userAgent: GEMINI_USER_AGENT });

      // Parse cookies — strips attributes like Path, Domain, Expires
      const cookiePairs = parseCookies(cookie);
      await context.addCookies(
        cookiePairs.map(({ name, value }) => ({
          name,
          value,
          domain: ".google.com",
          path: "/",
          secure: true,
        }))
      );

      const page = await context.newPage();

      // Capture first StreamGenerate response
      let responseText = "";
      let captured = false;
      const responsePromise = new Promise<void>((resolve) => {
        page.on("response", async (resp: any) => {
          if (captured || !resp.url().includes("StreamGenerate")) return;
          captured = true;
          try {
            const raw = await resp.text();
            responseText = parseStreamResponse(raw);
          } catch {
            /* ignore */
          }
          resolve();
        });
      });

      await page.goto(GEMINI_URL, { waitUntil: "domcontentloaded", timeout: 20000 });
      if (signal?.aborted) {
        throw signal.reason instanceof Error ? signal.reason : new Error("Request aborted");
      }
      await page.waitForTimeout(3000);

      // Type and send message
      const inputEl = await page.waitForSelector(".ql-editor, [contenteditable='true']", {
        timeout: 10000,
      });
      await inputEl.click();
      await page.keyboard.type(prompt, { delay: 10 });
      await page.waitForTimeout(300);
      await page.keyboard.press("Enter");

      // Wait for response or timeout
      await Promise.race([responsePromise, page.waitForTimeout(30000)]);
      if (signal?.aborted) {
        throw signal.reason instanceof Error ? signal.reason : new Error("Request aborted");
      }

      if (!responseText) {
        return {
          response: new Response(JSON.stringify({ error: "No response from Gemini" }), {
            status: 502,
            headers: { "Content-Type": "application/json" },
          }),
          url: GEMINI_URL,
          headers: {},
          transformedBody: body,
        };
      }

      const modelId = model || "gemini-2.5-pro";

      if (stream) {
        // Pseudo-streaming: send complete response as single SSE chunk
        // Gemini's StreamGenerate returns complete responses, not chunked streams
        const encoder = new TextEncoder();
        const readable = new ReadableStream(
          {
            start(controller) {
              controller.enqueue(
                encoder.encode(
                  `data: ${JSON.stringify(formatStreamChunk(responseText, modelId))}\n\n`
                )
              );
              controller.enqueue(
                encoder.encode(
                  `data: ${JSON.stringify(formatStreamChunk("", modelId, "stop"))}\n\n`
                )
              );
              controller.enqueue(encoder.encode("data: [DONE]\n\n"));
              controller.close();
            },
          },
          { highWaterMark: 16384 }
        );
        return {
          response: new Response(readable, {
            status: 200,
            headers: {
              "Content-Type": "text/event-stream",
              "Cache-Control": "no-cache",
              Connection: "keep-alive",
            },
          }),
          url: GEMINI_URL,
          headers: {},
          transformedBody: body,
        };
      }

      return {
        response: new Response(JSON.stringify(formatChatCompletion(responseText, modelId)), {
          status: 200,
          headers: { "Content-Type": "application/json" },
        }),
        url: GEMINI_URL,
        headers: {},
        transformedBody: body,
      };
    } catch (error) {
      const rawMessage = error instanceof Error ? error.message : "Unknown error";
      // #3516: a missing Playwright browser is a host/config problem, not a transient upstream
      // fault. Surface an actionable error and tag it with the connection-cooldown hint so
      // accountFallback skips the provider circuit breaker and applies a short, non-exponential
      // cooldown instead of looping on a retryable 500.
      if (isMissingBrowserExecutable(rawMessage)) {
        return {
          response: new Response(
            JSON.stringify({
              error:
                "Gemini Web requires the Playwright Chromium browser, which is not installed. " +
                "Run `npx playwright install chromium` on the host (or rebuild the Docker image with browsers).",
            }),
            {
              status: 503,
              headers: {
                "Content-Type": "application/json",
                "X-Omni-Fallback-Hint": "connection_cooldown",
              },
            }
          ),
          url: GEMINI_URL,
          headers: {},
          transformedBody: body,
        };
      }
      return {
        response: new Response(
          JSON.stringify({
            error: sanitizeErrorMessage(rawMessage),
          }),
          { status: 500, headers: { "Content-Type": "application/json" } }
        ),
        url: GEMINI_URL,
        headers: {},
        transformedBody: body,
      };
    } finally {
      if (abortBrowser) signal?.removeEventListener("abort", abortBrowser);
      // Always close browser to prevent resource leaks
      if (browser) {
        try {
          await browser.close();
        } catch {
          /* ignore close errors */
        }
      }
    }
  }
}