import { Router } from "express";
import { z } from "zod";

import { type LearningOrchestrator } from "../learning/orchestrator.js";
import { logger } from "../logger.js";
import { MemoryStore } from "../memory/store.js";
import { type ResultReferenceResolver } from "../results/resolver.js";
import { RESULT_REFERENCE_KIND } from "../results/store.js";
import { type OpencodeRuntimeAdapter } from "../runtime/opencode.js";
import { type ChatSessionBridge } from "../chat/sessionBridge.js";
import { toActorKey } from "../utils/fileStore.js";
import {
  buildPromptWithLearningContext,
  generateSessionTitle,
  getConversationTurnStats,
} from "./chatSession.js";
import {
  collectTextContent,
  streamPromptResponse,
  supportedModels,
  type SupportedModel,
} from "./chatStream.js";

const payloadSchema = z.object({
  message: z.string().min(1).max(10000),
  session_id: z.string().max(128).optional(),
  model: z.enum(supportedModels).optional(),
});

const abortPayloadSchema = z.object({
  session_id: z.string().max(128),
});

const forkPayloadSchema = z.object({
  session_id: z.string().max(128).optional(),
  keep_message_count: z.coerce.number().int().min(0),
});

export const buildChatRouter = (
  sessionBridge: ChatSessionBridge,
  runtime: OpencodeRuntimeAdapter,
  memoryStore: MemoryStore,
  learningOrchestrator: LearningOrchestrator,
  resultReferenceResolver: ResultReferenceResolver,
) => {
  const chatRouter = Router();

  chatRouter.get("/render-ref/:renderRef", async (req, res) => {
    const renderRef = req.params.renderRef?.trim();
    const userId = req.header("x-user-id")?.trim();
    const projectId = req.header("x-project-id") ?? undefined;
    const clientSessionId =
      typeof req.query.session_id === "string"
        ? req.query.session_id.trim()
        : undefined;

    if (!userId) {
      res.status(400).json({
        message: "x-user-id is required",
      });
      return;
    }

    if (!renderRef) {
      res.status(400).json({
        message: "render_ref is required",
      });
      return;
    }

    const result = await resultReferenceResolver.getFullAuthorized(
      renderRef,
      {
        actorKey: toActorKey(userId),
        clientSessionId,
        projectId,
      },
      {
        expectedKind: RESULT_REFERENCE_KIND.renderJunctionsPayload,
      },
    );

    if (!result) {
      res.status(404).json({ message: "render_ref not found" });
      return;
    }

    res.json(result);
  });

  chatRouter.post("/abort", async (req, res) => {
    const parsed = abortPayloadSchema.safeParse(req.body);
    if (!parsed.success) {
      res.status(400).json({
        message: "invalid request payload",
        detail: parsed.error.flatten(),
      });
      return;
    }

    try {
      const authHeader = req.header("authorization");
      const accessToken = authHeader?.startsWith("Bearer ")
        ? authHeader.slice("Bearer ".length)
        : authHeader;
      const projectId = req.header("x-project-id") ?? undefined;
      const traceId = req.header("x-trace-id") ?? undefined;
      const userId = req.header("x-user-id") ?? undefined;

      const binding = await sessionBridge.abort({
        clientSessionId: parsed.data.session_id,
        accessToken,
        projectId,
        traceId,
        userId,
      });

      if (!binding) {
        res.status(204).end();
        return;
      }

      logger.info(
        {
          clientSessionId: parsed.data.session_id,
          sessionId: binding.sessionId,
          traceId,
          projectId,
        },
        "aborted chat session by client request",
      );
      res.status(202).json({
        session_id: parsed.data.session_id,
        aborted: true,
      });
    } catch (error) {
      const detail = error instanceof Error ? error.message : String(error);
      logger.error({ err: error }, "chat abort failed");
      res.status(500).json({
        message: "chat abort failed",
        detail,
      });
    }
  });

  chatRouter.post("/fork", async (req, res) => {
    const parsed = forkPayloadSchema.safeParse(req.body);
    if (!parsed.success) {
      res.status(400).json({
        message: "invalid request payload",
        detail: parsed.error.flatten(),
      });
      return;
    }

    try {
      const authHeader = req.header("authorization");
      const accessToken = authHeader?.startsWith("Bearer ")
        ? authHeader.slice("Bearer ".length)
        : authHeader;
      const projectId = req.header("x-project-id") ?? undefined;
      const traceId = req.header("x-trace-id") ?? undefined;
      const userId = req.header("x-user-id") ?? undefined;

      const { binding, requestContext } = await sessionBridge.fork({
        clientSessionId: parsed.data.session_id,
        accessToken,
        projectId,
        traceId,
        keepMessageCount: parsed.data.keep_message_count,
        userId,
      });

      logger.info(
        {
          sourceClientSessionId: parsed.data.session_id,
          clientSessionId: requestContext.clientSessionId,
          sessionId: binding.sessionId,
          traceId: requestContext.traceId,
          projectId: requestContext.projectId,
          keepMessageCount: parsed.data.keep_message_count,
        },
        "forked chat session",
      );

      res.status(200).json({
        session_id: requestContext.clientSessionId,
      });
    } catch (error) {
      const detail = error instanceof Error ? error.message : String(error);
      logger.error({ err: error }, "chat fork failed");
      res.status(500).json({
        message: "chat fork failed",
        detail,
      });
    }
  });

  chatRouter.post("/stream", async (req, res) => {
    const parsed = payloadSchema.safeParse(req.body);
    if (!parsed.success) {
      res.status(400).json({
        message: "invalid request payload",
        detail: parsed.error.flatten(),
      });
      return;
    }

    try {
      const authHeader = req.header("authorization");
      const accessToken = authHeader?.startsWith("Bearer ")
        ? authHeader.slice("Bearer ".length)
        : authHeader;
      const projectId = req.header("x-project-id") ?? undefined;
      const traceId = req.header("x-trace-id") ?? undefined;
      const userId = req.header("x-user-id") ?? undefined;

      const { binding, requestContext, created } = await sessionBridge.resolve({
        clientSessionId: parsed.data.session_id,
        accessToken,
        projectId,
        traceId,
        userId,
      });

      logger.info(
        {
          clientSessionId: requestContext.clientSessionId,
          sessionId: binding.sessionId,
          created,
          model: parsed.data.model,
          traceId: requestContext.traceId,
          projectId: requestContext.projectId,
        },
        "processing chat request",
      );

      res.status(200);
      res.setHeader("Content-Type", "text/event-stream; charset=utf-8");
      res.setHeader("Cache-Control", "no-cache");
      res.setHeader("Connection", "keep-alive");
      res.setHeader("X-Accel-Buffering", "no");
      res.flushHeaders?.();

      const clientSessionId = requestContext.clientSessionId;
      let streamClosed = false;
      const abortController = new AbortController();
      const handleClientClose = () => {
        if (streamClosed || abortController.signal.aborted) {
          return;
        }
        abortController.abort();
      };

      req.on("close", handleClientClose);
      res.on("close", handleClientClose);

      try {
        const preparedMessage = await buildPromptWithLearningContext(
          memoryStore,
          requestContext.actorKey,
          requestContext.projectKey,
          parsed.data.message,
        );
        const streamResult = await streamPromptResponse({
          runtime,
          opencodeSessionId: binding.sessionId,
          clientSessionId,
          message: preparedMessage,
          model: parsed.data.model,
          traceId: requestContext.traceId,
          projectId: requestContext.projectId,
          signal: abortController.signal,
          write: (event, data) => {
            if (streamClosed || res.writableEnded || res.destroyed) {
              return;
            }
            res.write(toSse(event, data));
          },
        });

        if (!streamResult.aborted && !streamResult.failed) {
          const messages = await runtime.messages(binding.sessionId, 60);
          const assistantMessage = [...messages]
            .reverse()
            .find((message) => message.info.role === "assistant");
          const assistantText = collectTextContent(assistantMessage?.parts ?? []);
          const existingSessionTitle = sessionBridge.getSessionTitle(binding.sessionId);
          let sessionTitle = existingSessionTitle;
          const { userMessageCount, assistantMessageCount } =
            await getConversationTurnStats(runtime, binding.sessionId);
          const shouldGenerateTitle =
            userMessageCount <= 3 &&
            assistantMessageCount >= 1;
          if (shouldGenerateTitle) {
            sessionTitle = await generateSessionTitle(runtime, {
              sessionId: binding.sessionId,
              latestUserMessage: parsed.data.message,
              fallbackTitle: existingSessionTitle,
            });
            if (sessionTitle !== existingSessionTitle) {
              sessionBridge.setSessionTitle(binding.sessionId, sessionTitle);
            }
          }
          if (!streamClosed && !res.writableEnded && !res.destroyed) {
            if (
              shouldGenerateTitle &&
              sessionTitle &&
              sessionTitle !== existingSessionTitle
            ) {
              res.write(
                toSse("session_title", {
                  session_id: clientSessionId,
                  title: sessionTitle,
                }),
              );
            }
          }
          if (assistantText) {
            void learningOrchestrator.onTurnCompleted({
              assistantMessage: assistantText,
              model: parsed.data.model,
              requestContext,
              sessionId: binding.sessionId,
              toolCallCount: streamResult.toolCallCount,
              userMessage: parsed.data.message,
            }).catch((error) => {
              logger.warn(
                { err: error, sessionId: binding.sessionId },
                "post-turn learning failed",
              );
            });
          }
        }
      } finally {
        streamClosed = true;
        req.off("close", handleClientClose);
        res.off("close", handleClientClose);
      }

      if (!res.writableEnded && !res.destroyed) {
        res.end();
      }
    } catch (error) {
      const detail = error instanceof Error ? error.message : String(error);
      logger.error({ err: error }, "chat stream failed");
      res.status(500).json({
        message: "chat stream failed",
        detail,
      });
    }
  });

  return chatRouter;
};

const toSse = (event: string, data: Record<string, unknown>) =>
  `event: ${event}\ndata: ${JSON.stringify(data)}\n\n`;