import { runResearch } from "@/lib/llm";
import type { ComparisonRequest } from "@/lib/llm/types";
import type { ComparisonData } from "@/lib/types";
import { db } from "@/lib/db";
import { comparisons, comparisonItems } from "@/lib/db/schema";
import { eq } from "drizzle-orm";
import { createId } from "@paralleldrive/cuid2";

function serializeSSE(event: string, data: unknown): string {
  return `event: ${event}\ndata: ${JSON.stringify(data)}\n\n`;
}

function slugify(text: string): string {
  return text
    .toLowerCase()
    .replace(/[^a-z0-9]+/g, "-")
    .replace(/^-|-$/g, "")
    .slice(0, 200);
}

export async function POST(request: Request) {
  const body: { query?: string; items?: string[]; dimensions?: string[] } =
    await request.json();
  const { query, items, dimensions } = body;

  if (!items || items.length < 2) {
    return Response.json(
      { error: "At least 2 items are required" },
      { status: 400 }
    );
  }

  const id = createId();
  const title = `Comparing ${items.join(" vs ")}`;
  const slug = `${slugify(title)}-${id.slice(-6)}`;

  await db.insert(comparisons).values({
    id,
    title,
    query: query || null,
    slug,
    status: "researching",
  });

  const encoder = new TextEncoder();

  const stream = new ReadableStream({
    async start(controller) {
      const researchRequest: ComparisonRequest = {
        query: query || "",
        items,
        dimensions,
      };

      let itemsCompleted = 0;

      try {
        for await (const progress of runResearch(researchRequest)) {
          if (progress.stage === "parsing") {
            controller.enqueue(
              encoder.encode(
                serializeSSE("progress", {
                  status: "researching",
                  message: progress.message,
                  itemsCompleted: 0,
                  totalItems: items.length,
                  currentStep: progress.message,
                })
              )
            );
          }

          if (progress.stage === "researching") {
            itemsCompleted++;
            controller.enqueue(
              encoder.encode(
                serializeSSE("progress", {
                  status: "researching",
                  message: `Researching ${progress.item}...`,
                  itemsCompleted,
                  totalItems: items.length,
                  currentStep: `Analyzing ${progress.item}`,
                })
              )
            );
          }

          if (progress.stage === "synthesizing") {
            controller.enqueue(
              encoder.encode(
                serializeSSE("progress", {
                  status: "researching",
                  message: progress.message,
                  itemsCompleted: items.length,
                  totalItems: items.length,
                  currentStep: "Synthesizing results",
                })
              )
            );
          }

          if (progress.stage === "complete") {
            const result = progress.result;

            const comparisonData: Omit<ComparisonData, "id" | "userId" | "slug" | "tags" | "isPublic" | "viewCount" | "createdAt" | "updatedAt"> = {
              title,
              query: query || "",
              status: "completed",
              summary: `${result.summary}\n\nRecommendation: ${result.recommendation}`,
              items: result.items.map((item) => ({
                name: item.name,
                description: item.description,
                overallScore: item.overallScore,
                dimensions: item.dimensions,
                pros: item.pros,
                cons: item.cons,
              })),
              dimensions: result.dimensions,
            };

            await db
              .update(comparisons)
              .set({
                status: "completed",
                summary: comparisonData.summary,
                overallData:
                  comparisonData as unknown as Record<string, unknown>,
                updatedAt: new Date(),
              })
              .where(eq(comparisons.id, id));

            for (let i = 0; i < result.items.length; i++) {
              const item = result.items[i];
              await db.insert(comparisonItems).values({
                id: createId(),
                comparisonId: id,
                name: item.name,
                description: item.description,
                researchData: item as unknown as Record<string, unknown>,
                scores:
                  item.dimensions as unknown as Record<string, unknown>,
                pros: item.pros,
                cons: item.cons,
                order: i,
              });
            }

            controller.enqueue(
              encoder.encode(
                serializeSSE("progress", {
                  status: "completed",
                  message: "Research complete!",
                  itemsCompleted: items.length,
                  totalItems: items.length,
                  currentStep: "Done",
                })
              )
            );

            controller.enqueue(
              encoder.encode(
                serializeSSE("done", { id, slug, data: comparisonData })
              )
            );
          }

          if (progress.stage === "error") {
            await db
              .update(comparisons)
              .set({
                status: "failed",
                updatedAt: new Date(),
              })
              .where(eq(comparisons.id, id));

            controller.enqueue(
              encoder.encode(
                serializeSSE("progress", {
                  status: "failed",
                  message: progress.error,
                  itemsCompleted,
                  totalItems: items.length,
                  currentStep: "Failed",
                })
              )
            );
          }
        }
      } catch (error) {
        await db
          .update(comparisons)
          .set({ status: "failed", updatedAt: new Date() })
          .where(eq(comparisons.id, id));

        controller.enqueue(
          encoder.encode(
            serializeSSE("progress", {
              status: "failed",
              message: error instanceof Error ? error.message : "Unknown error",
              itemsCompleted,
              totalItems: items.length,
              currentStep: "Failed",
            })
          )
        );
      }

      controller.close();
    },
  });

  return new Response(stream, {
    headers: {
      "Content-Type": "text/event-stream",
      "Cache-Control": "no-cache",
      Connection: "keep-alive",
    },
  });
}