import { NextResponse } from "next/server";
import {
  chatSessionCreateInsertRow,
  chatSessionCreateSchema,
  ChatSessionBodyTooLargeError,
  readChatSessionJson,
} from "@/lib/chat-session-write-contract";
import { consumeUserRequestRateLimit } from "@/lib/request-rate-limit";
import { resolveInheritedContextSummary } from "@/lib/session-context-summary";
import { isSupabaseConfigurationError } from "@/lib/supabase/config";
import { createServerSupabaseClient } from "@/lib/supabase/server";
import {
  clampSessionLimit,
  nextSessionCursor,
  parseSessionCursor,
  sessionCursorFilter,
} from "@/lib/session-cursor";
import { excludeEmptyConsultations } from "@/lib/session-list-filter";

const SESSION_LIST_COLUMNS = "id,title,theme,model_id,session_type,rectification_case_id,chart_profile_id,chart_profile_name,chart_profile_role,updated_at,pinned,archived_at";

export async function GET(request: Request) {
  try {
    const url = new URL(request.url);
    const limit = clampSessionLimit(url.searchParams.get("limit"));
    const beforeRaw = url.searchParams.get("before");
    const cursor = parseSessionCursor(beforeRaw);
    if (beforeRaw && !cursor) {
      return NextResponse.json({ error: "聊天记录请求无效" }, { status: 400 });
    }
    const supabase = await createServerSupabaseClient();
    const { data: { user }, error: authError } = await supabase.auth.getUser();
    if (authError || !user) return NextResponse.json({ error: "请先登录" }, { status: 401 });

    let pageQuery = excludeEmptyConsultations(
      supabase
        .from("chat_sessions")
        .select(SESSION_LIST_COLUMNS)
        .eq("user_id", user.id)
        .eq("pinned", false)
        .is("archived_at", null),
    )
      .order("updated_at", { ascending: false })
      .order("id", { ascending: false })
      .limit(limit + 1);
    if (cursor) {
      pageQuery = pageQuery.or(sessionCursorFilter(cursor));
    }
    const { data: pageRows, error: pageError } = await pageQuery;
    if (pageError) return NextResponse.json({ error: "聊天记录暂时无法读取" }, { status: 500 });

    let pinnedRows: typeof pageRows = [];
    if (!cursor) {
      const { data: pinnedData, error: pinnedError } = await excludeEmptyConsultations(
        supabase
          .from("chat_sessions")
          .select(SESSION_LIST_COLUMNS)
          .eq("user_id", user.id)
          .eq("pinned", true)
          .is("archived_at", null),
      )
        .order("updated_at", { ascending: false })
        .order("id", { ascending: false });
      if (pinnedError) return NextResponse.json({ error: "聊天记录暂时无法读取" }, { status: 500 });
      pinnedRows = pinnedData ?? [];
    }

    const nextCursor = nextSessionCursor(pageRows ?? [], limit);
    const page = (pageRows ?? []).slice(0, limit);
    const sessions = cursor ? page : [...(pinnedRows ?? []), ...page];
    return NextResponse.json({ sessions, nextCursor });
  } catch (error) {
    if (isSupabaseConfigurationError(error)) {
      return NextResponse.json({ error: "数据库尚未配置", code: "DATABASE_NOT_CONFIGURED" }, { status: 503 });
    }
    return NextResponse.json({ error: "聊天记录暂时无法读取" }, { status: 500 });
  }
}

export async function POST(request: Request) {
  try {
    const supabase = await createServerSupabaseClient();
    const { data: { user }, error: authError } = await supabase.auth.getUser();
    if (authError || !user) return NextResponse.json({ error: "请先登录" }, { status: 401 });
    const limited = consumeUserRequestRateLimit("sessionWrite", user.id);
    if (!limited.ok) {
      return NextResponse.json({
        error: "请求过于频繁",
        code: "rate_limited",
        retryAfterSeconds: limited.retryAfterSeconds,
      }, { status: 429, headers: { "Retry-After": String(limited.retryAfterSeconds) } });
    }
    const parsed = chatSessionCreateSchema.safeParse(await readChatSessionJson(request));
    if (!parsed.success) return NextResponse.json({ error: "聊天记录格式不正确" }, { status: 400 });
    const { id, updated_at: _ignoredClientClock, continued_from_session_id: continuedFromSessionId, ...values } = parsed.data;
    const inheritedSummary = await resolveInheritedContextSummary({
      continuedFromSessionId,
      loadOwnedSummary: async (sourceId) => {
        const { data } = await supabase
          .from("chat_sessions")
          .select("context_summary")
          .eq("id", sourceId)
          .eq("user_id", user.id)
          .maybeSingle();
        return data?.context_summary ?? null;
      },
    });
    const { error } = await supabase.from("chat_sessions").insert(
      chatSessionCreateInsertRow({
        id,
        userId: user.id,
        values,
        inheritedSummary,
        updatedAt: new Date().toISOString(),
      }),
    );
    if (error) return NextResponse.json({ error: "聊天记录暂时无法同步" }, { status: 500 });
    return NextResponse.json({ ok: true }, { status: 201 });
  } catch (error) {
    if (error instanceof ChatSessionBodyTooLargeError) {
      return NextResponse.json({ error: error.message }, { status: 413 });
    }
    if (isSupabaseConfigurationError(error)) {
      return NextResponse.json({ error: "数据库尚未配置", code: "DATABASE_NOT_CONFIGURED" }, { status: 503 });
    }
    return NextResponse.json({ error: "聊天记录暂时无法同步" }, { status: 500 });
  }
}