import fs from 'fs';
import path from 'path';
import { defineTool, ToolError } from 'libllmorbiter';
import { pdfToText, splitPdfPages, pdfToPng } from 'pdfconvert-wasm';
import { prepareVfs, syncVfsToDb } from './vfs.js';

const IMAGE_FOLDER = 'images';
const DEFAULT_DPI = 150;

/**
 * Normalizes format input to 'txt', 'png', or 'both'.
 * @param {string} [format]
 * @returns {'txt'|'png'|'both'}
 */
function normalizeFormat(format) {
    if (!format || typeof format !== 'string') return 'txt';
    const f = format.trim().toLowerCase();
    if (f === 'png' || f === 'image' || f === 'images') return 'png';
    if (f === 'both' || f === 'all') return 'both';
    return 'txt';
}

/**
 * Slugifies a filename base for safe image output names.
 * @param {string} filename
 * @returns {string}
 */
function slugifyBase(filename) {
    const base = path.basename(filename, path.extname(filename));
    const cleaned = String(base || '')
        .toLowerCase()
        .replace(/[^a-z0-9.]+/g, '-')
        .replace(/-+/g, '-')
        .replace(/^-|-$/g, '');
    return cleaned.slice(0, 40) || 'document';
}

/**
 * Creates the pdf_read tool.
 * @param {{ googleAuthId: number }} ctx
 */
export function createPdfReadTool({ googleAuthId }) {
    return defineTool({
        name: 'pdf_read',
        description:
            'Read and convert PDF/text documents to text or VFS PNG images (stored in "images/").',
        strict: false,
        parameters: {
            type: 'object',
            additionalProperties: false,
            required: ['path'],
            properties: {
                path: {
                    type: 'string',
                    description: 'VFS path or HTTP(S) URL.',
                },
                format: {
                    type: 'string',
                    enum: ['txt', 'png', 'both'],
                    description: 'Output format: "txt" (layout text), "png" (page images), "both". Default "txt".',
                },
                page: {
                    type: 'number',
                    description: '1-based page number. Omit for all pages.',
                },
                dpi: {
                    type: 'number',
                    description: 'PNG render DPI. Default 150.',
                },
            },
        },
        invoke: async ({ path: inputPath, file, format, type, page, dpi = DEFAULT_DPI } = {}) => {
            const rawPath = typeof inputPath === 'string' ? inputPath.trim() : typeof file === 'string' ? file.trim() : '';
            if (!rawPath) {
                throw new ToolError('pdf_read requires a non-empty "path" (e.g. "document.pdf").');
            }

            const targetFormat = normalizeFormat(format || type);
            const targetPage = Number.isInteger(Number(page)) && Number(page) >= 1 ? Number(page) : null;
            const targetDpi = Number.isInteger(Number(dpi)) && Number(dpi) >= 50 && Number(dpi) <= 600 ? Number(dpi) : DEFAULT_DPI;

            const vfsRoot = await prepareVfs({ googleAuthId });
            let buffer = null;
            let displayPath = rawPath;

            if (rawPath.startsWith('http://') || rawPath.startsWith('https://')) {
                try {
                    const res = await fetch(rawPath, { signal: AbortSignal.timeout(15_000) });
                    if (!res.ok) {
                        throw new Error(`${res.status} ${res.statusText}`);
                    }
                    buffer = Buffer.from(await res.arrayBuffer());
                } catch (err) {
                    throw new ToolError(`pdf_read: network failure downloading URL (${rawPath}): ${err.message}`);
                }
            } else {
                const clean = rawPath.replace(/^([a-zA-Z]:|\/)+/, '').replace(/^\.\/+/, '');
                const abs = path.resolve(vfsRoot, clean);
                const rel = path.relative(vfsRoot, abs);
                if (rel.startsWith('..') || path.isAbsolute(rel)) {
                    throw new ToolError(`Access denied: path "${rawPath}" escapes virtual filesystem boundary.`);
                }
                displayPath = rel;

                if (!fs.existsSync(abs) || !fs.statSync(abs).isFile()) {
                    throw new ToolError(`File not found: "${rawPath}". Check the path with find_files.`);
                }
                buffer = fs.readFileSync(abs);
            }

            if (!buffer || buffer.length === 0) {
                throw new ToolError(`File is empty: "${rawPath}".`);
            }

            const isPdf = buffer.subarray(0, 5).toString('ascii').startsWith('%PDF') || rawPath.toLowerCase().endsWith('.pdf');

            // Plain text fallback if non-PDF
            if (!isPdf) {
                const text = buffer.toString('utf-8');
                return {
                    path: displayPath,
                    format: 'txt',
                    totalPages: 1,
                    text,
                };
            }

            // PDF processing via pdfconvert-wasm
            // Always clone as isolated Uint8Array so WASM worker does not detach shared buffers.
            const pdfBytes = Uint8Array.from(buffer);

            const result = {
                path: displayPath,
                format: targetFormat,
            };

            // 1. Text conversion
            if (targetFormat === 'txt' || targetFormat === 'both') {
                try {
                    if (targetPage) {
                        const pageText = await pdfToText(pdfBytes, {
                            layout: true,
                            firstPage: targetPage,
                            lastPage: targetPage,
                        });
                        result.page = targetPage;
                        result.text = pageText;
                    } else {
                        const text = await pdfToText(pdfBytes, { layout: true });
                        const pages = splitPdfPages(text);
                        result.totalPages = pages.length;
                        result.text = text;
                        result.pages = pages.map((t, idx) => ({ pageNumber: idx + 1, text: t }));
                    }
                } catch (err) {
                    throw new ToolError(`pdf_read: failed to extract text from PDF: ${err.message}`);
                }
            }

            // 2. PNG conversion
            if (targetFormat === 'png' || targetFormat === 'both') {
                try {
                    const options = { dpi: targetDpi };
                    if (targetPage) {
                        options.firstPage = targetPage;
                        options.lastPage = targetPage;
                    }

                    const images = await pdfToPng(Uint8Array.from(buffer), options);
                    const imagesDir = path.join(vfsRoot, IMAGE_FOLDER);
                    fs.mkdirSync(imagesDir, { recursive: true });

                    const baseSlug = slugifyBase(displayPath);
                    const savedImages = [];

                    for (const img of images) {
                        const filename = `${baseSlug}-page-${img.pageNumber}.png`;
                        const absImgPath = path.join(imagesDir, filename);
                        const relImgPath = `${IMAGE_FOLDER}/${filename}`;

                        fs.writeFileSync(absImgPath, Buffer.from(img.data));
                        savedImages.push({
                            pageNumber: img.pageNumber,
                            path: relImgPath,
                            bytes: img.data.length,
                        });
                    }

                    if (savedImages.length > 0) {
                        try {
                            await syncVfsToDb({ googleAuthId, vfsRoot });
                        } catch (err) {
                            console.warn('[pdf_read] failed to sync rendered images to VFS DB:', err?.message || err);
                        }
                    }

                    result.images = savedImages;
                    if (!result.totalPages) result.totalPages = images.length;
                    result.note =
                        'Rendered page PNGs saved to VFS. Use analyze_image to inspect them or embed them with markdown `![Page](path)`.';
                } catch (err) {
                    throw new ToolError(`pdf_read: failed to render PDF to PNG: ${err.message}`);
                }
            }

            return result;
        },
    });
}