import { EventRouter, buildNewSessionUpdate } from "@/modules/eventRouter";
import { type Fastify } from "../types";
import { db } from "@/storage/db";
import { z } from "zod";
import { Prisma } from "@prisma/client";
import { log } from "@/utils/log";
import { randomKeyNaked } from "@/utils/randomKeyNaked";
import { allocateUserSeq } from "@/storage/seq";

export function registerSessionRoutes(app: Fastify, eventRouter: EventRouter) {

    // Sessions API
    app.get('/v1/sessions', {
        preHandler: app.authenticate,
    }, async (request, reply) => {
        const userId = request.userId;

        const sessions = await db.session.findMany({
            where: { accountId: userId },
            orderBy: { updatedAt: 'desc' },
            take: 150,
            select: {
                id: true,
                seq: true,
                createdAt: true,
                updatedAt: true,
                metadata: true,
                metadataVersion: true,
                agentState: true,
                agentStateVersion: true,
                active: true,
                lastActiveAt: true,
                // messages: {
                //     orderBy: { seq: 'desc' },
                //     take: 1,
                //     select: {
                //         id: true,
                //         seq: true,
                //         content: true,
                //         localId: true,
                //         createdAt: true
                //     }
                // }
            }
        });

        return reply.send({
            sessions: sessions.map((v) => {
                // const lastMessage = v.messages[0];
                const sessionUpdatedAt = v.updatedAt.getTime();
                // const lastMessageCreatedAt = lastMessage ? lastMessage.createdAt.getTime() : 0;

                return {
                    id: v.id,
                    seq: v.seq,
                    createdAt: v.createdAt.getTime(),
                    updatedAt: sessionUpdatedAt,
                    active: v.active,
                    activeAt: v.lastActiveAt.getTime(),
                    metadata: v.metadata,
                    metadataVersion: v.metadataVersion,
                    agentState: v.agentState,
                    agentStateVersion: v.agentStateVersion,
                    lastMessage: null
                };
            })
        });
    });

    // V2 Sessions API - Active sessions only
    app.get('/v2/sessions/active', {
        preHandler: app.authenticate,
        schema: {
            querystring: z.object({
                limit: z.coerce.number().int().min(1).max(500).default(150)
            }).optional()
        }
    }, async (request, reply) => {
        const userId = request.userId;
        const limit = request.query?.limit || 150;

        const sessions = await db.session.findMany({
            where: {
                accountId: userId,
                active: true,
                lastActiveAt: { gt: new Date(Date.now() - 1000 * 60 * 15) /* 15 minutes */ }
            },
            orderBy: { lastActiveAt: 'desc' },
            take: limit,
            select: {
                id: true,
                seq: true,
                createdAt: true,
                updatedAt: true,
                metadata: true,
                metadataVersion: true,
                agentState: true,
                agentStateVersion: true,
                active: true,
                lastActiveAt: true,
            }
        });

        return reply.send({
            sessions: sessions.map((v) => ({
                id: v.id,
                seq: v.seq,
                createdAt: v.createdAt.getTime(),
                updatedAt: v.updatedAt.getTime(),
                active: v.active,
                activeAt: v.lastActiveAt.getTime(),
                metadata: v.metadata,
                metadataVersion: v.metadataVersion,
                agentState: v.agentState,
                agentStateVersion: v.agentStateVersion,
            }))
        });
    });

    // V2 Sessions API - Cursor-based pagination with change tracking
    app.get('/v2/sessions', {
        preHandler: app.authenticate,
        schema: {
            querystring: z.object({
                cursor: z.string().optional(),
                limit: z.coerce.number().int().min(1).max(200).default(50),
                changedSince: z.coerce.number().int().positive().optional()
            }).optional()
        }
    }, async (request, reply) => {
        const userId = request.userId;
        const { cursor, limit = 50, changedSince } = request.query || {};

        // Decode cursor - simple ID-based cursor
        let cursorSessionId: string | undefined;
        if (cursor) {
            if (cursor.startsWith('cursor_v1_')) {
                cursorSessionId = cursor.substring(10);
            } else {
                return reply.code(400).send({ error: 'Invalid cursor format' });
            }
        }

        // Build where clause
        const where: Prisma.SessionWhereInput = { accountId: userId };

        // Add changedSince filter (just a filter, doesn't affect pagination)
        if (changedSince) {
            where.updatedAt = {
                gt: new Date(changedSince)
            };
        }

        // Add cursor pagination - always by ID descending (most recent first)
        if (cursorSessionId) {
            where.id = {
                lt: cursorSessionId  // Get sessions with ID less than cursor (for desc order)
            };
        }

        // Always sort by ID descending for consistent pagination
        const orderBy = { id: 'desc' as const };

        const sessions = await db.session.findMany({
            where,
            orderBy,
            take: limit + 1, // Fetch one extra to determine if there are more
            select: {
                id: true,
                seq: true,
                createdAt: true,
                updatedAt: true,
                metadata: true,
                metadataVersion: true,
                agentState: true,
                agentStateVersion: true,
                active: true,
                lastActiveAt: true,
            }
        });

        // Check if there are more results
        const hasNext = sessions.length > limit;
        const resultSessions = hasNext ? sessions.slice(0, limit) : sessions;

        // Generate next cursor - simple ID-based cursor
        let nextCursor: string | null = null;
        if (hasNext && resultSessions.length > 0) {
            const lastSession = resultSessions[resultSessions.length - 1];
            nextCursor = `cursor_v1_${lastSession.id}`;
        }

        return reply.send({
            sessions: resultSessions.map((v) => ({
                id: v.id,
                seq: v.seq,
                createdAt: v.createdAt.getTime(),
                updatedAt: v.updatedAt.getTime(),
                active: v.active,
                activeAt: v.lastActiveAt.getTime(),
                metadata: v.metadata,
                metadataVersion: v.metadataVersion,
                agentState: v.agentState,
                agentStateVersion: v.agentStateVersion,
            })),
            nextCursor,
            hasNext
        });
    });

    // Create or load session by tag
    app.post('/v1/sessions', {
        schema: {
            body: z.object({
                tag: z.string(),
                metadata: z.string(),
                agentState: z.string().nullish()
            })
        },
        preHandler: app.authenticate
    }, async (request, reply) => {
        const userId = request.userId;
        const { tag, metadata } = request.body;

        const session = await db.session.findFirst({
            where: {
                accountId: userId,
                tag: tag
            }
        });
        if (session) {
            log({ module: 'session-create', sessionId: session.id, userId, tag }, `Found existing session: ${session.id} for tag ${tag}`);
            return reply.send({
                session: {
                    id: session.id,
                    seq: session.seq,
                    metadata: session.metadata,
                    metadataVersion: session.metadataVersion,
                    agentState: session.agentState,
                    agentStateVersion: session.agentStateVersion,
                    active: session.active,
                    activeAt: session.lastActiveAt.getTime(),
                    createdAt: session.createdAt.getTime(),
                    updatedAt: session.updatedAt.getTime(),
                    lastMessage: null
                }
            });
        } else {

            // Resolve seq
            const updSeq = await allocateUserSeq(userId);

            // Create session
            log({ module: 'session-create', userId, tag }, `Creating new session for user ${userId} with tag ${tag}`);
            const session = await db.session.create({
                data: {
                    accountId: userId,
                    tag: tag,
                    metadata: metadata
                }
            });
            log({ module: 'session-create', sessionId: session.id, userId }, `Session created: ${session.id}`);

            // Emit new session update
            const updatePayload = buildNewSessionUpdate(session, updSeq, randomKeyNaked(12));
            log({
                module: 'session-create',
                userId,
                sessionId: session.id,
                updateType: 'new-session',
                updatePayload: JSON.stringify(updatePayload)
            }, `Emitting new-session update to all user connections`);
            eventRouter.emitUpdate({
                userId,
                payload: updatePayload,
                recipientFilter: { type: 'all-user-authenticated-connections' }
            });

            return reply.send({
                session: {
                    id: session.id,
                    seq: session.seq,
                    metadata: session.metadata,
                    metadataVersion: session.metadataVersion,
                    agentState: session.agentState,
                    agentStateVersion: session.agentStateVersion,
                    active: session.active,
                    activeAt: session.lastActiveAt.getTime(),
                    createdAt: session.createdAt.getTime(),
                    updatedAt: session.updatedAt.getTime(),
                    lastMessage: null
                }
            });
        }
    });

    app.get('/v1/sessions/:sessionId/messages', {
        schema: {
            params: z.object({
                sessionId: z.string()
            })
        },
        preHandler: app.authenticate
    }, async (request, reply) => {
        const userId = request.userId;
        const { sessionId } = request.params;

        // Verify session belongs to user
        const session = await db.session.findFirst({
            where: {
                id: sessionId,
                accountId: userId
            }
        });

        if (!session) {
            return reply.code(404).send({ error: 'Session not found' });
        }

        const messages = await db.sessionMessage.findMany({
            where: { sessionId },
            orderBy: { createdAt: 'desc' },
            take: 150,
            select: {
                id: true,
                seq: true,
                localId: true,
                content: true,
                createdAt: true,
                updatedAt: true
            }
        });

        return reply.send({
            messages: messages.map((v) => ({
                id: v.id,
                seq: v.seq,
                content: v.content,
                localId: v.localId,
                createdAt: v.createdAt.getTime(),
                updatedAt: v.updatedAt.getTime()
            }))
        });
    });
}