import type { Message, MessageEntity, MessagePart } from '~/composables/useChat';
import { buildFocusedMessageTree, buildMessageTree } from '~~/utils/message';

type TopicExportSource = {
    id: string;
    name: string;
    agentId: string;
    createdAt: Date | string;
    messages: MessageEntity[];
};

const sanitizeFilename = (name: string): string => {
    const cleaned = name
        .trim()
        .replace(/[<>:"/\\|?*\u0000-\u001f]/g, '')
        .replace(/\s+/g, ' ')
        .slice(0, 80)
        .trim();

    return cleaned.length > 0 ? cleaned : 'topic';
};

const downloadBlob = (content: string, filename: string, mimeType: string) => {
    const blob = new Blob([content], { type: mimeType });
    const url = URL.createObjectURL(blob);
    const anchor = document.createElement('a');
    anchor.href = url;
    anchor.download = filename;
    document.body.appendChild(anchor);
    anchor.click();
    document.body.removeChild(anchor);
    URL.revokeObjectURL(url);
};

const serializePart = (part: MessagePart) => ({
    id: part.id,
    type: part.type,
    content: part.content,
    finished: part.finished,
    createdAt: part.createdAt,
    lastUpdatedAt: part.lastUpdatedAt,
    toolCall: part.toolCall
        ? {
            id: part.toolCall.id,
            toolName: part.toolCall.toolName,
            status: part.toolCall.status,
            input: part.toolCall.input,
            output: part.toolCall.output,
            error: part.toolCall.error,
            createdAt: part.toolCall.createdAt,
        }
        : null,
});

const serializeMessageEntity = (message: MessageEntity) => ({
    id: message.id,
    role: message.role,
    content: message.content,
    parentMessageId: message.parentMessageId,
    generationId: message.generationId,
    activeChildId: message.activeChildId,
    deleted: message.deleted,
    createdAt: message.createdAt,
    updatedAt: message.updatedAt,
    parts: (message.parts || []).map(serializePart),
    generation: message.generation
        ? {
            id: message.generation.id,
            modelId: message.generation.modelId,
            status: message.generation.status,
            tokens: message.generation.tokens,
            error: message.generation.error,
        }
        : null,
    attachments: (message.attachments || []).map((attachment) => ({
        id: attachment.id,
        fileId: attachment.fileId,
        createdAt: attachment.createdAt,
        file: {
            id: attachment.file.id,
            name: attachment.file.name,
            mimeType: attachment.file.mimeType,
            size: attachment.file.size,
            url: attachment.file.url,
        },
    })),
});

const serializeMessageTree = (message: Message): ReturnType<typeof serializeMessageEntity> & {
    children: ReturnType<typeof serializeMessageEntity>[];
} => ({
    ...serializeMessageEntity(message),
    children: (message.children || [])
        .filter((child): child is MessageEntity => child !== undefined)
        .map((child) => serializeMessageTree(child as Message)),
});

const formatMessageAsMarkdown = (message: MessageEntity): string => {
    const roleLabel = message.role === 'user' ? 'User' : 'Assistant';
    const sections: string[] = [`### ${roleLabel}`];

    if (message.role === 'user') {
        if (message.content) {
            sections.push(message.content);
        }

        if ((message.attachments || []).length > 0) {
            const attachmentLines = message.attachments.map((attachment) => {
                return `- Attachment: ${attachment.file.name} (${attachment.file.mimeType})`;
            });
            sections.push(attachmentLines.join('\n'));
        }
    } else {
        const partSections: string[] = [];

        for (const part of message.parts || []) {
            switch (part.type) {
                case 'text': {
                    if (part.content) {
                        partSections.push(part.content);
                    }
                    break;
                }
                case 'reasoning': {
                    if (part.content) {
                        partSections.push(`<details>\n<summary>Reasoning</summary>\n\n${part.content}\n</details>`);
                    }
                    break;
                }
                case 'tool-call': {
                    const toolName = part.toolCall?.toolName ?? 'tool';
                    const status = part.toolCall?.status ?? 'unknown';
                    const input = part.toolCall?.input
                        ? JSON.stringify(part.toolCall.input, null, 2)
                        : '';
                    const output = part.toolCall?.output
                        ? JSON.stringify(part.toolCall.output, null, 2)
                        : part.toolCall?.error
                            ? JSON.stringify(part.toolCall.error, null, 2)
                            : '';

                    partSections.push([
                        `#### Tool: ${toolName} (${status})`,
                        input ? `\`\`\`json\n${input}\n\`\`\`` : '',
                        output ? `\`\`\`json\n${output}\n\`\`\`` : '',
                    ].filter(Boolean).join('\n\n'));
                    break;
                }
            }
        }

        if (partSections.length > 0) {
            sections.push(partSections.join('\n\n'));
        } else if (message.content) {
            sections.push(message.content);
        }
    }

    return sections.join('\n\n');
};

const fetchTopicForExport = async (topicId: string): Promise<TopicExportSource | null> => {
    try {
        const topic = await $fetch<TopicExportSource>(`/api/topic/${topicId}`);
        return topic;
    } catch (error) {
        console.error('Failed to fetch topic for export:', error);
        return null;
    }
};

export const exportTopicToJson = async (topicId: string) => {
    const topic = await fetchTopicForExport(topicId);
    if (!topic) return;

    const messageTree = buildMessageTree(topic.messages || []);
    const payload = {
        version: 1,
        exportedAt: new Date().toISOString(),
        format: 'json' as const,
        includesRegenerations: true,
        topic: {
            id: topic.id,
            name: topic.name,
            agentId: topic.agentId,
            createdAt: topic.createdAt,
        },
        messages: messageTree.map(serializeMessageTree),
    };

    downloadBlob(
        JSON.stringify(payload, null, 2),
        `${sanitizeFilename(topic.name)}.json`,
        'application/json',
    );
};

export const exportTopicToMarkdown = async (topicId: string) => {
    const topic = await fetchTopicForExport(topicId);
    if (!topic) return;

    const messageTree = buildMessageTree(topic.messages || []);
    const focusedMessages = buildFocusedMessageTree(messageTree);
    const body = focusedMessages
        .filter((message) => message.deleted !== true)
        .map(formatMessageAsMarkdown)
        .join('\n\n---\n\n');

    const markdown = [
        `# ${topic.name}`,
        '',
        `> Exported from Veridian on ${new Date().toISOString()}`,
        `> Focused conversation only (regenerations excluded)`,
        '',
        body || '_No messages in focused conversation._',
        '',
    ].join('\n');

    downloadBlob(
        markdown,
        `${sanitizeFilename(topic.name)}.md`,
        'text/markdown',
    );
};