/**
 * CardForge - SillyTavern Character Studio
 * Advanced PNG metadata handling and character management
 */

class CardForge {
    constructor() {
        this.currentCharacter = this.getDefaultCharacter();
        this.extractedCharacter = null;
        this.currentAvatar = null;
        this.crc32Table = this.generateCRC32Table();
    }

    getDefaultCharacter() {
        return {
            name: '',
            description: '',
            personality: '',
            scenario: '',
            first_mes: '',
            mes_example: '',
            creatorcomment: '',
            creator: '',
            character_version: '',
            tags: [],
            data: {}
        };
    }

    generateCRC32Table() {
        const table = new Int32Array(256);
        for (let i = 0; i < 256; i++) {
            let c = i;
            for (let k = 0; k < 8; k++) {
                c = (c & 1) ? (0xedb88320 ^ (c >>> 1)) : (c >>> 1);
            }
            table[i] = c;
        }
        return table;
    }

    calculateCRC32(bytes) {
        let c = -1;
        for (let i = 0; i < bytes.length; i++) {
            c = this.crc32Table[(c ^ bytes[i]) & 0xff] ^ (c >>> 8);
        }
        return c ^ -1;
    }

    stringToUint8Array(str) {
        return new TextEncoder().encode(str);
    }

    uint8ArrayToString(arr) {
        return new TextDecoder().decode(arr);
    }

    /**
     * Reads all chunks from a PNG file
     */
    readPNGChunks(arrayBuffer) {
        const view = new DataView(arrayBuffer);
        const chunks = [];
        let offset = 8; // Skip PNG signature (8 bytes)

        // PNG signature verification: 89 50 4E 47 0D 0A 1A 0A
        const signature = new Uint8Array(arrayBuffer, 0, 8);
        const expectedSignature = [0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A];
        
        if (!expectedSignature.every((byte, i) => byte === signature[i])) {
            throw new Error('Invalid PNG signature');
        }

        while (offset < arrayBuffer.byteLength) {
            const length = view.getUint32(offset, false); // Big-endian
            const type = this.uint8ArrayToString(new Uint8Array(arrayBuffer, offset + 4, 4));
            const data = new Uint8Array(arrayBuffer, offset + 8, length);
            const crc = view.getUint32(offset + 8 + length, false);

            chunks.push({
                type,
                data,
                crc,
                offset,
                length
            });

            offset += 12 + length;

            if (type === 'IEND') break;
        }

        return chunks;
    }

    /**
     * Creates a PNG chunk (tEXt, iTXt, etc.)
     */
    createChunk(type, data) {
        const typeBytes = this.stringToUint8Array(type);
        const length = data.length;
        
        // Create chunk structure: [length:4][type:4][data:N][crc:4]
        const chunk = new Uint8Array(4 + 4 + length + 4);
        const view = new DataView(chunk.buffer);

        // Length
        view.setUint32(0, length, false);
        
        // Type
        chunk.set(typeBytes, 4);
        
        // Data
        chunk.set(data, 8);
        
        // CRC32 of type + data
        const crcData = new Uint8Array(chunk.buffer, 4, 4 + length);
        const crc = this.calculateCRC32(crcData);
        view.setUint32(8 + length, crc >>> 0, false);

        return chunk;
    }

    /**
     * Embeds SillyTavern metadata into PNG
     */
    embedMetadata(pngBuffer, characterData) {
        try {
            const chunks = this.readPNGChunks(pngBuffer);
            
            // Prepare metadata
            const metadata = {
                ...characterData,
                spec: 'chara_card_v2',
                spec_version: '2.0',
                data: {
                    ...characterData.data,
                    name: characterData.name,
                    description: characterData.description,
                    personality: characterData.personality,
                    scenario: characterData.scenario,
                    first_mes: characterData.first_mes,
                    mes_example: characterData.mes_example,
                    creatorcomment: characterData.creatorcomment,
                    tags: characterData.tags,
                    creator: characterData.creator,
                    character_version: characterData.character_version
                }
            };

            // Convert to base64
            const jsonStr = JSON.stringify(metadata);
            const base64Data = btoa(unescape(encodeURIComponent(jsonStr)));
            
            // Create tEXt chunk with keyword 'chara'
            const textContent = `chara\u0000${base64Data}`;
            const textData = this.stringToUint8Array(textContent);
            
            // Find insertion point (before first IDAT or at end if no IDAT)
            let insertIndex = chunks.findIndex(c => c.type === 'IDAT');
            if (insertIndex === -1) insertIndex = chunks.length;
            
            // Create new chunk array
            const newChunk = {
                type: 'tEXt',
                data: textData,
                crc: 0
            };

            chunks.splice(insertIndex, 0, newChunk);

            // Rebuild PNG
            return this.rebuildPNG(chunks);
            
        } catch (error) {
            console.error('Error embedding metadata:', error);
            throw new Error('Failed to embed metadata: ' + error.message);
        }
    }

    /**
     * Rebuilds PNG file from chunks
     */
    rebuildPNG(chunks) {
        // Calculate total size
        let totalSize = 8; // PNG signature
        
        // Calculate chunk sizes
        for (const chunk of chunks) {
            totalSize += 12 + chunk.data.length; // 4 (length) + 4 (type) + N (data) + 4 (crc)
        }

        const result = new Uint8Array(totalSize);
        const view = new DataView(result.buffer);
        let offset = 0;

        // Write PNG signature
        const signature = [0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A];
        result.set(signature, offset);
        offset += 8;

        // Write chunks
        for (const chunk of chunks) {
            // Length
            view.setUint32(offset, chunk.data.length, false);
            offset += 4;

            // Type
            const typeBytes = this.stringToUint8Array(chunk.type);
            result.set(typeBytes, offset);
            offset += 4;

            // Data
            result.set(chunk.data, offset);
            offset += chunk.data.length;

            // CRC
            if (chunk.crc && chunk.crc !== 0) {
                view.setUint32(offset, chunk.crc >>> 0, false);
            } else {
                // Calculate CRC for new chunks
                const crcData = new Uint8Array(result.buffer, offset - 4 - chunk.data.length, 4 + chunk.data.length);
                const crc = this.calculateCRC32(crcData);
                view.setUint32(offset, crc >>> 0, false);
            }
            offset += 4;
        }

        return result.buffer;
    }

    /**
     * Extracts metadata from PNG
     */
    extractMetadata(pngBuffer) {
        try {
            const chunks = this.readPNGChunks(pngBuffer);
            
            // Look for tEXt chunks with 'chara' keyword
            for (const chunk of chunks) {
                if (chunk.type === 'tEXt') {
                    const text = this.uint8ArrayToString(chunk.data);
                    
                    // Check for chara keyword (format: "chara\0<base64>")
                    if (text.startsWith('chara\u0000')) {
                        const base64Data = text.substring(6);
                        const jsonStr = decodeURIComponent(escape(atob(base64Data)));
                        const data = JSON.parse(jsonStr);
                        
                        return {
                            success: true,
                            data: this.normalizeCharacterData(data),
                            format: 'PNG tEXt (SillyTavern)',
                            raw: data
                        };
                    }
                }
                
                // Also check iTXt chunks (international text, UTF-8)
                if (chunk.type === 'iTXt') {
                    const text = this.uint8ArrayToString(chunk.data);
                    if (text.includes('chara')) {
                        // Parse iTXt format: keyword\0compression\0language\0translated\0text
                        const parts = text.split('\u0000');
                        if (parts[0] === 'chara' && parts.length >= 5) {
                            const base64Data = parts[4];
                            const jsonStr = decodeURIComponent(escape(atob(base64Data)));
                            const data = JSON.parse(jsonStr);
                            
                            return {
                                success: true,
                                data: this.normalizeCharacterData(data),
                                format: 'PNG iTXt (SillyTavern)',
                                raw: data
                            };
                        }
                    }
                }
            }

            return {
                success: false,
                error: 'No character metadata found in PNG chunks',
                errorCode: 'NO_METADATA'
            };

        } catch (error) {
            return {
                success: false,
                error: error.message,
                errorCode: 'PARSE_ERROR'
            };
        }
    }

    /**
     * Normalizes character data from various formats (v1, v2, v3)
     */
    normalizeCharacterData(data) {
        // Handle V2 format with nested data object
        if (data.data && typeof data.data === 'object') {
            return {
                name: data.data.name || data.name || '',
                description: data.data.description || data.description || '',
                personality: data.data.personality || data.personality || '',
                scenario: data.data.scenario || data.scenario || '',
                first_mes: data.data.first_mes || data.first_mes || '',
                mes_example: data.data.mes_example || data.mes_example || '',
                creatorcomment: data.data.creatorcomment || data.creatorcomment || '',
                creator: data.data.creator || data.creator || '',
                character_version: data.data.character_version || data.character_version || '1.0',
                tags: data.data.tags || data.tags || [],
                spec: data.spec || 'unknown',
                spec_version: data.spec_version || '1.0',
                data: data.data
            };
        }

        // Handle V1 flat format
        return {
            name: data.name || '',
            description: data.description || '',
            personality: data.personality || '',
            scenario: data.scenario || '',
            first_mes: data.first_mes || '',
            mes_example: data.mes_example || '',
            creatorcomment: data.creatorcomment || '',
            creator: data.creator || '',
            character_version: data.character_version || '1.0',
            tags: data.tags || [],
            spec: data.spec || 'chara_card_v1',
            spec_version: data.spec_version || '1.0',
            data: data.data || {}
        };
    }

    /**
     * Validates character data
     */
    validateCharacter(data) {
        const errors = [];
        
        if (!data.name || data.name.trim() === '') {
            errors.push('Character name is required');
        }
        
        if (data.name && data.name.length > 100) {
            errors.push('Character name is too long (max 100 characters)');
        }

        return {
            valid: errors.length === 0,
            errors
        };
    }

    /**
     * Generates a placeholder avatar with initials
     */
    generatePlaceholderAvatar(name, width = 400, height = 600) {
        const canvas = document.createElement('canvas');
        canvas.width = width;
        canvas.height = height;
        const ctx = canvas.getContext('2d');

        // Background gradient
        const gradient = ctx.createLinearGradient(0, 0, width, height);
        gradient