feat: character utils

src/lib/utils/characters/index.ts

+import CRC32 from 'crc-32';
+
+export const parseFile = async (file) => {
+	if (file.type === 'application/json') {
+		return await parseJsonFile(file);
+	} else if (file.type === 'image/png') {
+		return await parsePngFile(file);
+	} else {
+		throw new Error('Unsupported file type');
+	}
+};
+
+const parseJsonFile = async (file) => {
+	const text = await file.text();
+	const json = JSON.parse(text);
+
+	const character = extractCharacter(json);
+
+	return {
+		file,
+		json,
+		formats: detectFormats(json),
+		character
+	};
+};
+
+const parsePngFile = async (file) => {
+	const arrayBuffer = await file.arrayBuffer();
+	const text = parsePngText(arrayBuffer);
+	const json = JSON.parse(text);
+
+	const image = URL.createObjectURL(file);
+	const character = extractCharacter(json);
+
+	return {
+		file,
+		json,
+		image,
+		formats: detectFormats(json),
+		character
+	};
+};
+
+const parsePngText = (arrayBuffer) => {
+	const textChunkKeyword = 'chara';
+	const chunks = readPngChunks(new Uint8Array(arrayBuffer));
+
+	const textChunk = chunks
+		.filter((chunk) => chunk.type === 'tEXt')
+		.map((chunk) => decodeTextChunk(chunk.data))
+		.find((entry) => entry.keyword === textChunkKeyword);
+
+	if (!textChunk) {
+		throw new Error(`No PNG text chunk named "${textChunkKeyword}" found`);
+	}
+
+	try {
+		return new TextDecoder().decode(Uint8Array.from(atob(textChunk.text), (c) => c.charCodeAt(0)));
+	} catch (e) {
+		throw new Error('Unable to parse "chara" field as base64', e);
+	}
+};
+
+const readPngChunks = (data) => {
+	const isValidPng =
+		data[0] === 0x89 &&
+		data[1] === 0x50 &&
+		data[2] === 0x4e &&
+		data[3] === 0x47 &&
+		data[4] === 0x0d &&
+		data[5] === 0x0a &&
+		data[6] === 0x1a &&
+		data[7] === 0x0a;
+
+	if (!isValidPng) throw new Error('Invalid PNG file');
+
+	let chunks = [];
+	let offset = 8; // Skip PNG signature
+
+	while (offset < data.length) {
+		let length =
+			(data[offset] << 24) | (data[offset + 1] << 16) | (data[offset + 2] << 8) | data[offset + 3];
+		let type = String.fromCharCode.apply(null, data.slice(offset + 4, offset + 8));
+		let chunkData = data.slice(offset + 8, offset + 8 + length);
+		let crc =
+			(data[offset + 8 + length] << 24) |
+			(data[offset + 8 + length + 1] << 16) |
+			(data[offset + 8 + length + 2] << 8) |
+			data[offset + 8 + length + 3];
+
+		if (CRC32.buf(chunkData, CRC32.str(type)) !== crc) {
+			throw new Error(`Invalid CRC for chunk type "${type}"`);
+		}
+
+		chunks.push({ type, data: chunkData, crc });
+		offset += 12 + length;
+	}
+
+	return chunks;
+};
+
+const decodeTextChunk = (data) => {
+	let i = 0;
+	const keyword = [];
+	const text = [];
+
+	for (; i < data.length && data[i] !== 0; i++) {
+		keyword.push(String.fromCharCode(data[i]));
+	}
+
+	for (i++; i < data.length; i++) {
+		text.push(String.fromCharCode(data[i]));
+	}
+
+	return { keyword: keyword.join(''), text: text.join('') };
+};
+
+const extractCharacter = (json) => {
+	function getTrimmedValue(json, keys) {
+		return keys.map((key) => json[key]).find((value) => value && value.trim());
+	}
+
+	const name = getTrimmedValue(json, ['char_name', 'name']);
+	const summary = getTrimmedValue(json, ['personality', 'title']);
+	const personality = getTrimmedValue(json, ['char_persona', 'description']);
+	const scenario = getTrimmedValue(json, ['world_scenario', 'scenario']);
+	const greeting = getTrimmedValue(json, ['char_greeting', 'greeting', 'first_mes']);
+	const examples = getTrimmedValue(json, ['example_dialogue', 'mes_example', 'definition']);
+
+	return { name, summary, personality, scenario, greeting, examples };
+};
+
+const detectFormats = (json) => {
+	const formats = [];
+
+	if (
+		json.char_name &&
+		json.char_persona &&
+		json.world_scenario &&
+		json.char_greeting &&
+		json.example_dialogue
+	)
+		formats.push('Text Generation Character');
+	if (
+		json.name &&
+		json.personality &&
+		json.description &&
+		json.scenario &&
+		json.first_mes &&
+		json.mes_example
+	)
+		formats.push('TavernAI Character');
+	if (
+		json.character &&
+		json.character.name &&
+		json.character.title &&
+		json.character.description &&
+		json.character.greeting &&
+		json.character.definition
+	)
+		formats.push('CharacterAI Character');
+	if (
+		json.info &&
+		json.info.character &&
+		json.info.character.name &&
+		json.info.character.title &&
+		json.info.character.description &&
+		json.info.character.greeting
+	)
+		formats.push('CharacterAI History');
+
+	return formats;
+};