import { NextRequest, NextResponse } from "next/server";
import { prisma } from "@/lib/prisma";
import { Prisma } from "@agentlens/database";
import { validateApiKey } from "@/lib/api-key";
import { auth } from "@/auth";

// Types
interface DecisionPointPayload {
  id: string;
  type: "TOOL_SELECTION" | "ROUTING" | "RETRY" | "ESCALATION" | "MEMORY_RETRIEVAL" | "PLANNING" | "CUSTOM";
  reasoning?: string;
  chosen: Prisma.JsonValue;
  alternatives: Prisma.JsonValue[];
  contextSnapshot?: Prisma.JsonValue;
  durationMs?: number;
  costUsd?: number;
  parentSpanId?: string;
  timestamp: string;
}

interface SpanPayload {
  id: string;
  parentSpanId?: string;
  name: string;
  type: "LLM_CALL" | "TOOL_CALL" | "MEMORY_OP" | "CHAIN" | "AGENT" | "CUSTOM";
  input?: Prisma.JsonValue;
  output?: Prisma.JsonValue;
  tokenCount?: number;
  costUsd?: number;
  durationMs?: number;
  status: "RUNNING" | "COMPLETED" | "ERROR";
  statusMessage?: string;
  startedAt: string;
  endedAt?: string;
  metadata?: Prisma.JsonValue;
}

interface EventPayload {
  id: string;
  spanId?: string;
  type: "ERROR" | "RETRY" | "FALLBACK" | "CONTEXT_OVERFLOW" | "USER_FEEDBACK" | "CUSTOM";
  name: string;
  metadata?: Prisma.JsonValue;
  timestamp: string;
}

interface TracePayload {
  id: string;
  name: string;
  sessionId?: string;
  status: "RUNNING" | "COMPLETED" | "ERROR";
  tags: string[];
  metadata?: Prisma.JsonValue;
  totalCost?: number;
  totalTokens?: number;
  totalDuration?: number;
  startedAt: string;
  endedAt?: string;
  decisionPoints: DecisionPointPayload[];
  spans: SpanPayload[];
  events: EventPayload[];
}

interface BatchTracesRequest {
  traces: TracePayload[];
}

function topologicalSortSpans(spans: SpanPayload[]): SpanPayload[] {
  const byId = new Map(spans.map((s) => [s.id, s]));
  const sorted: SpanPayload[] = [];
  const visited = new Set<string>();

  function visit(span: SpanPayload) {
    if (visited.has(span.id)) return;
    visited.add(span.id);
    if (span.parentSpanId && byId.has(span.parentSpanId)) {
      visit(byId.get(span.parentSpanId)!);
    }
    sorted.push(span);
  }

  for (const span of spans) visit(span);
  return sorted;
}

// POST /api/traces — Batch ingest traces from SDK
export async function POST(request: NextRequest) {
  try {
    // Validate Authorization header
    const authHeader = request.headers.get("authorization");
    if (!authHeader || !authHeader.startsWith("Bearer ")) {
      return NextResponse.json({ error: "Missing or invalid Authorization header" }, { status: 401 });
    }

    const contentLength = parseInt(request.headers.get("content-length") ?? "0", 10);
    const MAX_BODY_SIZE = 10 * 1024 * 1024;
    if (contentLength > MAX_BODY_SIZE) {
      return NextResponse.json({ error: "Request body too large (max 10MB)" }, { status: 413 });
    }

    const rawApiKey = authHeader.slice(7);
    if (!rawApiKey) {
      return NextResponse.json({ error: "Missing API key in Authorization header" }, { status: 401 });
    }

    const keyValidation = await validateApiKey(rawApiKey);
    if (!keyValidation) {
      return NextResponse.json({ error: "Invalid API key" }, { status: 401 });
    }

    const { userId, subscription } = keyValidation;

    if (!subscription) {
      return NextResponse.json({ error: "No subscription found for this user" }, { status: 403 });
    }

    const tier = subscription.tier;
    const sessionsLimit = subscription.sessionsLimit;

    if (tier === "FREE") {
      const startOfToday = new Date();
      startOfToday.setUTCHours(0, 0, 0, 0);

      const dailyCount = await prisma.trace.count({
        where: {
          userId,
          createdAt: { gte: startOfToday },
        },
      });

      if (dailyCount >= sessionsLimit) {
        return NextResponse.json(
          {
            error: `Rate limit exceeded. Current plan: ${tier}. Limit: ${sessionsLimit}/day. Upgrade at /settings/billing`,
          },
          { status: 429 }
        );
      }
    } else {
      if (subscription.sessionsUsed >= sessionsLimit) {
        return NextResponse.json(
          {
            error: `Rate limit exceeded. Current plan: ${tier}. Limit: ${sessionsLimit}/month. Upgrade at /settings/billing`,
          },
          { status: 429 }
        );
      }
    }

    // Parse and validate request body
    const body: BatchTracesRequest = await request.json();
    if (!body.traces || !Array.isArray(body.traces)) {
      return NextResponse.json({ error: "Request body must contain a 'traces' array" }, { status: 400 });
    }

    if (body.traces.length === 0) {
      return NextResponse.json({ error: "Traces array cannot be empty" }, { status: 400 });
    }

    // Validate each trace payload
    for (const trace of body.traces) {
      if (!trace.id || typeof trace.id !== "string") {
        return NextResponse.json({ error: "Each trace must have a valid 'id' (string)" }, { status: 400 });
      }
      if (!trace.name || typeof trace.name !== "string") {
        return NextResponse.json({ error: "Each trace must have a valid 'name' (string)" }, { status: 400 });
      }
      if (!trace.startedAt || typeof trace.startedAt !== "string") {
        return NextResponse.json({ error: "Each trace must have a valid 'startedAt' (ISO date string)" }, { status: 400 });
      }
      if (!["RUNNING", "COMPLETED", "ERROR"].includes(trace.status)) {
        return NextResponse.json({ error: `Invalid trace status: ${trace.status}` }, { status: 400 });
      }
      if (!Array.isArray(trace.tags)) {
        return NextResponse.json({ error: "Trace tags must be an array" }, { status: 400 });
      }
      if (!Array.isArray(trace.decisionPoints)) {
        return NextResponse.json({ error: "Trace decisionPoints must be an array" }, { status: 400 });
      }
      if (!Array.isArray(trace.spans)) {
        return NextResponse.json({ error: "Trace spans must be an array" }, { status: 400 });
      }
      if (!Array.isArray(trace.events)) {
        return NextResponse.json({ error: "Trace events must be an array" }, { status: 400 });
      }

      // Validate decision points
      for (const dp of trace.decisionPoints) {
        if (!dp.id || typeof dp.id !== "string") {
          return NextResponse.json({ error: "Each decision point must have a valid 'id' (string)" }, { status: 400 });
        }
        if (!["TOOL_SELECTION", "ROUTING", "RETRY", "ESCALATION", "MEMORY_RETRIEVAL", "PLANNING", "CUSTOM"].includes(dp.type)) {
          return NextResponse.json({ error: `Invalid decision point type: ${dp.type}` }, { status: 400 });
        }
        if (!dp.timestamp || typeof dp.timestamp !== "string") {
          return NextResponse.json({ error: "Each decision point must have a valid 'timestamp' (ISO date string)" }, { status: 400 });
        }
        if (!Array.isArray(dp.alternatives)) {
          return NextResponse.json({ error: "Decision point alternatives must be an array" }, { status: 400 });
        }
      }

      // Validate spans
      for (const span of trace.spans) {
        if (!span.id || typeof span.id !== "string") {
          return NextResponse.json({ error: "Each span must have a valid 'id' (string)" }, { status: 400 });
        }
        if (!span.name || typeof span.name !== "string") {
          return NextResponse.json({ error: "Each span must have a valid 'name' (string)" }, { status: 400 });
        }
        if (!["LLM_CALL", "TOOL_CALL", "MEMORY_OP", "CHAIN", "AGENT", "CUSTOM"].includes(span.type)) {
          return NextResponse.json({ error: `Invalid span type: ${span.type}` }, { status: 400 });
        }
        if (!span.startedAt || typeof span.startedAt !== "string") {
          return NextResponse.json({ error: "Each span must have a valid 'startedAt' (ISO date string)" }, { status: 400 });
        }
        if (!["RUNNING", "COMPLETED", "ERROR"].includes(span.status)) {
          return NextResponse.json({ error: `Invalid span status: ${span.status}` }, { status: 400 });
        }
      }

      // Validate events
      for (const event of trace.events) {
        if (!event.id || typeof event.id !== "string") {
          return NextResponse.json({ error: "Each event must have a valid 'id' (string)" }, { status: 400 });
        }
        if (!event.name || typeof event.name !== "string") {
          return NextResponse.json({ error: "Each event must have a valid 'name' (string)" }, { status: 400 });
        }
        if (!["ERROR", "RETRY", "FALLBACK", "CONTEXT_OVERFLOW", "USER_FEEDBACK", "CUSTOM"].includes(event.type)) {
          return NextResponse.json({ error: `Invalid event type: ${event.type}` }, { status: 400 });
        }
        if (!event.timestamp || typeof event.timestamp !== "string") {
          return NextResponse.json({ error: "Each event must have a valid 'timestamp' (ISO date string)" }, { status: 400 });
        }
      }
    }

    // Upsert traces using interactive transaction to control insert order.
    // If a trace ID already exists, update the trace and replace all child
    // records (spans, decision points, events) so intermediate flushes and
    // final flushes both work seamlessly.
    const result = await prisma.$transaction(async (tx) => {
      const upserted: string[] = [];
      let newTraceCount = 0;

      for (const trace of body.traces) {
        const existing = await tx.trace.findUnique({
          where: { id: trace.id },
          select: { id: true, userId: true },
        });

        // Security: prevent cross-user trace overwrite
        if (existing && existing.userId !== userId) {
          continue; // skip traces owned by other users
        }

        const traceData = {
          name: trace.name,
          sessionId: trace.sessionId,
          status: trace.status,
          tags: trace.tags,
          metadata: trace.metadata as Prisma.InputJsonValue,
          totalCost: trace.totalCost,
          totalTokens: trace.totalTokens,
          totalDuration: trace.totalDuration,
          startedAt: new Date(trace.startedAt),
          endedAt: trace.endedAt ? new Date(trace.endedAt) : null,
        };

        await tx.trace.upsert({
          where: { id: trace.id },
          create: { id: trace.id, userId, ...traceData },
          update: traceData,
        });

        if (!existing) {
          newTraceCount++;
        }

        // 2. Delete existing child records (order matters for FK constraints:
        //    decision points reference spans, so delete decisions first)
        await tx.decisionPoint.deleteMany({ where: { traceId: trace.id } });
        await tx.event.deleteMany({ where: { traceId: trace.id } });
        await tx.span.deleteMany({ where: { traceId: trace.id } });

        // 3. Recreate spans (parents before children for self-referencing FK)
        if (trace.spans.length > 0) {
          const spanOrder = topologicalSortSpans(trace.spans);
          for (const span of spanOrder) {
            await tx.span.create({
              data: {
                id: span.id,
                traceId: trace.id,
                parentSpanId: span.parentSpanId,
                name: span.name,
                type: span.type,
                input: span.input as Prisma.InputJsonValue | undefined,
                output: span.output as Prisma.InputJsonValue | undefined,
                tokenCount: span.tokenCount,
                costUsd: span.costUsd,
                durationMs: span.durationMs,
                status: span.status,
                statusMessage: span.statusMessage,
                startedAt: new Date(span.startedAt),
                endedAt: span.endedAt ? new Date(span.endedAt) : null,
                metadata: span.metadata as Prisma.InputJsonValue | undefined,
              },
            });
          }
        }

        // 4. Recreate decision points
        if (trace.decisionPoints.length > 0) {
          const validSpanIds = new Set(trace.spans.map((s) => s.id));

          await tx.decisionPoint.createMany({
            data: trace.decisionPoints.map((dp) => ({
              id: dp.id,
              traceId: trace.id,
              type: dp.type,
              reasoning: dp.reasoning,
              chosen: dp.chosen as Prisma.InputJsonValue,
              alternatives: dp.alternatives as Prisma.InputJsonValue[],
              contextSnapshot: dp.contextSnapshot as Prisma.InputJsonValue | undefined,
              durationMs: dp.durationMs,
              costUsd: dp.costUsd,
              parentSpanId: dp.parentSpanId && validSpanIds.has(dp.parentSpanId) ? dp.parentSpanId : null,
              timestamp: new Date(dp.timestamp),
            })),
          });
        }

        // 5. Recreate events
        if (trace.events.length > 0) {
          await tx.event.createMany({
            data: trace.events.map((event) => ({
              id: event.id,
              traceId: trace.id,
              spanId: event.spanId,
              type: event.type,
              name: event.name,
              metadata: event.metadata as Prisma.InputJsonValue | undefined,
              timestamp: new Date(event.timestamp),
            })),
          });
        }

        upserted.push(trace.id);
      }

      if (newTraceCount > 0 && tier !== "FREE") {
        await tx.subscription.update({
          where: { id: subscription.id },
          data: { sessionsUsed: { increment: newTraceCount } },
        });
      }

      return upserted;
    });

    return NextResponse.json({ success: true, count: result.length }, { status: 200 });
  } catch (error) {
    if (error instanceof SyntaxError) {
      return NextResponse.json({ error: "Invalid JSON in request body" }, { status: 400 });
    }

    console.error("Error processing traces:", error);
    return NextResponse.json({ error: "Internal server error" }, { status: 500 });
  }
}

// GET /api/traces — List traces with pagination
export async function GET(request: NextRequest) {
  try {
    const session = await auth();
    if (!session?.user?.id) {
      return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
    }

    const { searchParams } = new URL(request.url);
    const page = parseInt(searchParams.get("page") ?? "1", 10);
    const limit = parseInt(searchParams.get("limit") ?? "20", 10);
    const status = searchParams.get("status");
    const search = searchParams.get("search");
    const sessionId = searchParams.get("sessionId");
    const tags = searchParams.get("tags");
    const sort = searchParams.get("sort") ?? "newest";
    const dateFrom = searchParams.get("dateFrom");
    const dateTo = searchParams.get("dateTo");

    // Validate pagination parameters
    if (isNaN(page) || page < 1) {
      return NextResponse.json({ error: "Invalid page parameter. Must be a positive integer." }, { status: 400 });
    }
    if (isNaN(limit) || limit < 1 || limit > 100) {
      return NextResponse.json({ error: "Invalid limit parameter. Must be between 1 and 100." }, { status: 400 });
    }

    // Validate status parameter if provided
    const validStatuses = ["RUNNING", "COMPLETED", "ERROR"];
    if (status && !validStatuses.includes(status)) {
      return NextResponse.json({ error: `Invalid status. Must be one of: ${validStatuses.join(", ")}` }, { status: 400 });
    }

    // Validate sort parameter
    const validSorts = ["newest", "oldest", "longest", "shortest", "costliest"];
    if (sort && !validSorts.includes(sort)) {
      return NextResponse.json({ error: `Invalid sort. Must be one of: ${validSorts.join(", ")}` }, { status: 400 });
    }

    // Validate date parameters
    if (dateFrom && isNaN(Date.parse(dateFrom))) {
      return NextResponse.json({ error: "Invalid dateFrom parameter. Must be a valid ISO date string." }, { status: 400 });
    }
    if (dateTo && isNaN(Date.parse(dateTo))) {
      return NextResponse.json({ error: "Invalid dateTo parameter. Must be a valid ISO date string." }, { status: 400 });
    }

    const where: Record<string, unknown> = { userId: session.user.id };
    if (status) {
      where.status = status;
    }
    if (search) {
      where.name = {
        contains: search,
        mode: "insensitive",
      };
    }
    if (sessionId) {
      where.sessionId = sessionId;
    }
    if (tags) {
      const tagList = tags.split(",").map((t) => t.trim()).filter(Boolean);
      if (tagList.length > 0) {
        where.tags = {
          hasSome: tagList,
        };
      }
    }
    if (dateFrom) {
      where.createdAt = {
        ...((where.createdAt as Prisma.TraceWhereInput) ?? {}),
        gte: new Date(dateFrom),
      };
    }
    if (dateTo) {
      where.createdAt = {
        ...((where.createdAt as Prisma.TraceWhereInput) ?? {}),
        lte: new Date(dateTo),
      };
    }

    // Build order by clause based on sort parameter
    let orderBy: Prisma.TraceOrderByWithRelationInput = {
      startedAt: "desc",
    };

    switch (sort) {
      case "oldest":
        orderBy = { startedAt: "asc" };
        break;
      case "longest":
        orderBy = { totalDuration: "desc" };
        break;
      case "shortest":
        orderBy = { totalDuration: "asc" };
        break;
      case "costliest":
        orderBy = { totalCost: "desc" };
        break;
      case "newest":
      default:
        orderBy = { startedAt: "desc" };
        break;
    }

    // Count total traces
    const total = await prisma.trace.count({ where });

    // Calculate pagination
    const skip = (page - 1) * limit;
    const totalPages = Math.ceil(total / limit);

    // Fetch traces with pagination
    const traces = await prisma.trace.findMany({
      where,
      include: {
        _count: {
          select: {
            decisionPoints: true,
            spans: true,
            events: true,
          },
        },
      },
      orderBy,
      skip,
      take: limit,
    });

    return NextResponse.json({
      traces,
      total,
      page,
      limit,
      totalPages,
    }, { status: 200 });
  } catch (error) {
    console.error("Error listing traces:", error);
    return NextResponse.json({ error: "Internal server error" }, { status: 500 });
  }
}