import dayjs from "dayjs";
import axios from "axios";
import OpenAI from "openai";
import { z } from "zod";
import { zodResponseFormat } from "openai/helpers/zod";
import { GetObjectCommand } from "@aws-sdk/client-s3";
import { Blob } from "buffer";
import { FastifyInstance } from "fastify";

import { s3 } from "./s3";
import { secrets } from "./secrets";

// Drizzle schema
import { vendors, accounts } from "../../db/schema";
import {eq} from "drizzle-orm";

let openai: OpenAI | null = null;

// ---------------------------------------------------------
// INITIALIZE OPENAI
// ---------------------------------------------------------
export const initOpenAi = async () => {
    openai = new OpenAI({
        apiKey: secrets.OPENAI_API_KEY,
    });
};

// ---------------------------------------------------------
// STREAM → BUFFER
// ---------------------------------------------------------
async function streamToBuffer(stream: any): Promise<Buffer> {
    return new Promise((resolve, reject) => {
        const chunks: Buffer[] = [];
        stream.on("data", (chunk: Buffer) => chunks.push(chunk));
        stream.on("error", reject);
        stream.on("end", () => resolve(Buffer.concat(chunks)));
    });
}

// ---------------------------------------------------------
// GPT RESPONSE FORMAT (Zod Schema)
// ---------------------------------------------------------
const InstructionFormat = z.object({
    invoice_number: z.string(),
    invoice_date: z.string(),
    invoice_duedate: z.string(),
    invoice_type: z.string(),
    delivery_type: z.string(),
    delivery_note_number: z.string(),
    reference: z.string(),
    issuer: z.object({
        id: z.number().nullable().optional(),
        name: z.string(),
        address: z.string(),
        phone: z.string(),
        email: z.string(),
        bank: z.string(),
        bic: z.string(),
        iban: z.string(),
    }),
    recipient: z.object({
        name: z.string(),
        address: z.string(),
        phone: z.string(),
        email: z.string(),
    }),
    invoice_items: z.array(
        z.object({
            description: z.string(),
            unit: z.string(),
            quantity: z.number(),
            total: z.number(),
            total_without_tax: z.number(),
            tax_rate: z.number(),
            ean: z.number().nullable().optional(),
            article_number: z.number().nullable().optional(),
            account_number: z.number().nullable().optional(),
            account_id: z.number().nullable().optional(),
        })
    ),
    subtotal: z.number(),
    tax_rate: z.number(),
    tax: z.number(),
    total: z.number(),
    terms: z.string(),
});

// ---------------------------------------------------------
// MAIN FUNCTION
// ---------------------------------------------------------
export const getInvoiceDataFromGPT = async function (
    server: FastifyInstance,
    file: any,
    tenantId: number,
    learningContext?: string
) {
    await initOpenAi();

    if (!openai) {
        throw new Error("OpenAI not initialized. Call initOpenAi() first.");
    }

    console.log(`📄 Reading invoice file ${file.id}`);

    // ---------------------------------------------------------
    // 1) DOWNLOAD PDF FROM S3
    // ---------------------------------------------------------
    let fileData: Buffer;

    try {
        const command = new GetObjectCommand({
            Bucket: secrets.S3_BUCKET,
            Key: file.path,
        });

        const response: any = await s3.send(command);
        fileData = await streamToBuffer(response.Body);
    } catch (err) {
        console.log(`❌ S3 Download failed for file ${file.id}`, err);
        return null;
    }

    // Only process PDFs
    if (!file.path.toLowerCase().endsWith(".pdf")) {
        server.log.warn(`Skipping non-PDF file ${file.id}`);
        return null;
    }

    const fileBlob = new Blob([fileData], { type: "application/pdf" });

    // ---------------------------------------------------------
    // 2) SEND FILE TO PDF → TEXT API
    // ---------------------------------------------------------
    const form = new FormData();
    form.append("fileInput", fileBlob, file.path.split("/").pop());
    form.append("outputFormat", "txt");

    let extractedText: string;

    try {
        const res = await axios.post(
            "http://23.88.52.85:8080/api/v1/convert/pdf/text",
            form,
            {
                headers: {
                    "Content-Type": "multipart/form-data",
                    Authorization: `Bearer ${secrets.STIRLING_API_KEY}`,
                },
            }
        );

        extractedText = res.data;
    } catch (err) {
        console.log("❌ PDF OCR API failed", err);
        return null;
    }

    // ---------------------------------------------------------
    // 3) LOAD VENDORS + ACCOUNTS (DRIZZLE)
    // ---------------------------------------------------------
    const vendorList = await server.db
        .select({ id: vendors.id, name: vendors.name })
        .from(vendors)
        .where(eq(vendors.tenant,tenantId));

    const accountList = await server.db
        .select({
            id: accounts.id,
            label: accounts.label,
            number: accounts.number,
        })
        .from(accounts);

    // ---------------------------------------------------------
    // 4) GPT ANALYSIS
    // ---------------------------------------------------------



    const completion = await openai.chat.completions.parse({
        model: "gpt-4o",
        store: true,
        response_format: zodResponseFormat(InstructionFormat as any, "instruction"),
        messages: [
            { role: "user", content: extractedText },
            {
                role: "user",
                content:
                    "You extract structured invoice data.\n\n" +
                    `VENDORS: ${JSON.stringify(vendorList)}\n` +
                    `ACCOUNTS: ${JSON.stringify(accountList)}\n\n` +
                    (learningContext
                        ? `HISTORICAL_PATTERNS: ${learningContext}\n\n`
                        : "") +
                    "Match issuer by name to vendor.id.\n" +
                    "Match invoice items to account id based on label/number.\n" +
                    "Use historical patterns as soft hints for vendor/account/payment mapping.\n" +
                    "Do not invent values when the invoice text contradicts the hints.\n" +
                    "Convert dates to YYYY-MM-DD.\n" +
                    "Keep invoice items in original order.\n",
            },
        ],
    });

    const parsed = completion.choices[0].message.parsed;

    console.log(`🧾 Extracted invoice data for file ${file.id}`);

    return parsed;
};