// Default page settings prepended to all compile() calls so the API never falls back to A4.
// Users can override with their own #set page() — Typst's last rule wins.
const DEFAULT_PAGE = `#set page(width: auto, height: auto, margin: 8pt, fill: white)\n`;

export default class Typst {
    messages: Map<string, { replyId: string; ownerId?: string }>;
    private readonly apiUrl = "https://typ.sirblob.co/v1/render";

    constructor() {
        this.messages = new Map();
    }

    addMessage(userMessage: string, responseMessage: string, ownerId?: string) { this.messages.set(userMessage, { replyId: responseMessage, ownerId }); }
    removeMessage(userMessage: string) { this.messages.delete(userMessage); }
    hasMessage(userMessage: string) { return this.messages.has(userMessage); }
    getResponse(userMessage: string) { return this.messages.get(userMessage)?.replyId; }
    getOwner(userMessage: string) { return this.messages.get(userMessage)?.ownerId; }
    findByReply(replyId: string): { userMessage?: string; ownerId?: string } | null {
        for (const [userMessage, data] of this.messages.entries()) {
            if (data.replyId === replyId) return { userMessage, ownerId: data.ownerId };
        }
        return null;
    }

    private get apiKey(): string {
        const key = process.env.TYPSTDRIVE_API_KEY;
        if (!key) throw new Error("TYPSTDRIVE_API_KEY environment variable is missing.");
        return key;
    }

    async compile(code: string, _options?: { cleanup?: boolean }): Promise<{ buffers?: Buffer[]; error?: string }> {
        try {
            const response = await fetch(this.apiUrl, {
                method: "POST",
                headers: {
                    "Authorization": `Bearer ${this.apiKey}`,
                    "Content-Type": "application/json",
                },
                body: JSON.stringify({ code: DEFAULT_PAGE + code, format: "png" }),
            });

            if (!response.ok) {
                const text = await response.text().catch(() => response.statusText);
                return { error: `TypstDrive API error ${response.status}: ${text}` };
            }

            const arrayBuffer = await response.arrayBuffer();
            return { buffers: [Buffer.from(arrayBuffer)] };
        } catch (error: any) {
            return { error: `TypstDrive request failed: ${error?.message ?? String(error)}` };
        }
    }

    async renderToImage(typstCode: string, metadata?: { topic?: string; difficulty?: string }): Promise<Buffer | null> {
        const metadataHeader = metadata ? `
#align(center)[
  #block(
    fill: rgb("#e0f2fe"),
    inset: 10pt,
    radius: 4pt,
    [
      #text(weight: "bold", size: 14pt)[Topic: ${metadata.topic || "N/A"}] \\
      #text(size: 12pt, fill: rgb("#64748b"))[Difficulty: ${metadata.difficulty || "N/A"}]
    ]
  )
]

#v(0.8em)
` : '';

        // 500pt wide keeps equations readable; height: auto sizes to content.
        // This #set page overrides the DEFAULT_PAGE prepended in compile().
        const styledCode = `
#set page(width: 500pt, height: auto, margin: 12pt, fill: white)
#set text(size: 16pt, font: "New Computer Modern")
#set par(justify: true, leading: 0.65em)
#set block(spacing: 1.2em)

${metadataHeader}${typstCode}
        `;

        const result = await this.compile(styledCode);
        if (result.error || !result.buffers || result.buffers.length === 0) {
            console.error("Typst render error:", result.error);
            return null;
        }

        return result.buffers[0];
    }
}