import type { ApiEnvelope } from "@/types/api";

export class ApiError extends Error {
    status: number;
    body: string;
    errors: unknown[];

    constructor(message: string, status: number, body: string, errors: unknown[] = []) {
        super(message);
        this.name = "ApiError";
        this.status = status;
        this.body = body;
        this.errors = errors;
    }
}

export async function requestJson<T>(input: RequestInfo | URL, init?: RequestInit): Promise<T> {
    const res = await fetch(input, init);
    const payload = await parseJsonResponse(res);
    const envelope = isApiEnvelope<T>(payload) ? payload : null;

    if (!res.ok) {
        const message = envelope?.message || `Request failed with status ${res.status}`;
        const body = envelope ? message : stringifyPayload(payload);
        throw new ApiError(message, res.status, body, envelope?.errors || []);
    }

    if (envelope) {
        if (envelope.status === "error") {
            throw new ApiError(envelope.message || "Request failed", res.status, JSON.stringify(envelope), envelope.errors);
        }
        return envelope.data;
    }

    return payload as T;
}

export function jsonRequestInit(method: string, body: unknown): RequestInit {
    return {
        method,
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify(body),
    };
}

async function parseJsonResponse(res: Response): Promise<unknown> {
    const text = await res.text();
    if (!text.length) return null;
    try {
        return JSON.parse(text);
    } catch {
        return text;
    }
}

function isApiEnvelope<T>(value: unknown): value is ApiEnvelope<T> {
    if (!value || typeof value !== "object" || Array.isArray(value)) return false;
    const source = value as Record<string, unknown>;
    return (
        "status" in source &&
        "data" in source &&
        "message" in source &&
        "errors" in source
    );
}

function stringifyPayload(payload: unknown): string {
    if (typeof payload === "string") return payload;
    try {
        return JSON.stringify(payload);
    } catch {
        return String(payload);
    }
}