import type {
    SerializedRequest,
    SerializedResponse,
} from "@suaveplan/api-types/sandbox-bridge";
import {
    buildFailResponsePayload,
    createInvoice,
    finaliseInvoice,
    getInvoiceOrThrow,
    type InMemoryStore,
    listInvoices,
    parseCreateInvoiceInput,
    raiseSubscriptionInactive,
} from "../domain/index.js";
import { getStore } from "./wasm-state.js";

/**
 * Routing + handler entry point for the wasm-tier surface. Receives a
 * `SerializedRequest` (the WASI-stdio envelope payload), matches against
 * the static route table by method + URL pathname, and dispatches to a
 * per-route handler that delegates every business decision to
 * `src/domain/invoice-rules.ts`.
 *
 * `SuaveplanError`-shaped throws are NOT caught here — the ABI shim
 * in `wasm-compiler-javy` wraps `handleRequest` and emits an
 * `{ kind: "error" }` envelope when a thrown `SuaveplanError` reaches
 * the boundary.
 */
export async function handleRequest(
    req: SerializedRequest
): Promise<SerializedResponse> {
    const url = new URL(req.url);
    const pathname = url.pathname;
    const store = getStore();
    const result = await dispatch({
        method: req.method.toUpperCase(),
        pathname,
        search: url.searchParams,
        body: decodeBody(req.bodyBase64),
        capabilities: req.capabilities,
        store,
    });
    return result;
}

interface DispatchCtx {
    readonly method: string;
    readonly pathname: string;
    readonly search: URLSearchParams;
    readonly body: Uint8Array;
    readonly capabilities: readonly string[];
    readonly store: InMemoryStore;
}

async function dispatch(ctx: DispatchCtx): Promise<SerializedResponse> {
    if (ctx.method === "GET" && ctx.pathname === "/example/public/ping") {
        return jsonResponse(200, {
            ok: true,
            pluginName: "@suaveplan/api-plugin-example",
        });
    }
    if (ctx.method === "GET" && ctx.pathname === "/example/health") {
        return jsonResponse(200, { ok: true });
    }
    if (ctx.method === "GET" && ctx.pathname === "/example/invoices") {
        const deny = rbacCheck(ctx.capabilities, "example:read");
        if (deny !== null) return deny;
        return jsonResponse(200, { invoices: listInvoices(ctx.store) });
    }
    if (ctx.method === "GET") {
        const id = matchInvoiceId(ctx.pathname);
        if (id !== null) {
            const deny = rbacCheck(ctx.capabilities, "example:read");
            if (deny !== null) return deny;
            return jsonResponse(200, getInvoiceOrThrow(ctx.store, id));
        }
    }
    if (ctx.method === "POST" && ctx.pathname === "/example/invoices") {
        const deny = rbacCheck(ctx.capabilities, "example:write");
        if (deny !== null) return deny;
        const parsedBody = parseRequestBody(ctx.body);
        const parsed = parseCreateInvoiceInput(parsedBody);
        if (!parsed.success) {
            return jsonResponse(400, {
                code: "VALIDATION_FAILED",
                issues: parsed.issues,
            });
        }
        const created = createInvoice(ctx.store, parsed.data);
        return jsonResponse(200, created);
    }
    if (ctx.method === "POST") {
        const finaliseId = matchFinaliseId(ctx.pathname);
        if (finaliseId !== null) {
            const deny = rbacCheck(ctx.capabilities, "example:write");
            if (deny !== null) return deny;
            // The trusted tier awaits a Promise here to keep its
            // Stripe-call histogram observation > 0 ms; the wasm tier
            // has no histogram to record so the await is a no-op.
            await Promise.resolve();
            const updated = finaliseInvoice(ctx.store, finaliseId);
            return jsonResponse(200, updated);
        }
    }
    if (ctx.method === "GET" && ctx.pathname === "/example/rate-limited") {
        return jsonResponse(200, { ok: true });
    }
    if (
        ctx.method === "GET" &&
        ctx.pathname === "/example/subscription-required"
    ) {
        return raiseSubscriptionInactive();
    }
    if (ctx.method === "GET" && ctx.pathname === "/_/test/fail-response") {
        const fail = ctx.search.get("failResponse") === "1";
        return jsonResponse(200, buildFailResponsePayload(fail));
    }
    return jsonResponse(404, { code: "ROUTE_NOT_FOUND", path: ctx.pathname });
}

function matchInvoiceId(pathname: string): string | null {
    const prefix = "/example/invoices/";
    if (!pathname.startsWith(prefix)) return null;
    const tail = pathname.slice(prefix.length);
    if (tail.length === 0 || tail.includes("/")) return null;
    return tail;
}

function matchFinaliseId(pathname: string): string | null {
    const prefix = "/example/invoices/";
    const suffix = "/finalise";
    if (!pathname.startsWith(prefix) || !pathname.endsWith(suffix)) return null;
    const id = pathname.slice(prefix.length, pathname.length - suffix.length);
    if (id.length === 0 || id.includes("/")) return null;
    return id;
}

function rbacCheck(
    capabilities: readonly string[],
    scope: string
): SerializedResponse | null {
    if (capabilities.includes(scope)) return null;
    return jsonResponse(403, {
        code: "RBAC_MISSING_SCOPE",
        requiredScope: scope,
        actualScopes: capabilities,
    });
}

function jsonResponse(status: number, payload: unknown): SerializedResponse {
    const body = JSON.stringify(payload);
    return {
        status,
        headers: [["content-type", "application/json"]],
        bodyBase64: encodeBase64Url(textToBytes(body)),
    };
}

/** Parse the request body bytes as JSON (or `undefined` when empty/invalid). */
function parseRequestBody(body: Uint8Array): unknown {
    if (body.length === 0) return undefined;
    const text = bytesToText(body);
    try {
        return JSON.parse(text);
    } catch {
        return undefined;
    }
}

/** Decode base64-url-no-pad to raw bytes. */
function decodeBody(base64Url: string): Uint8Array {
    if (base64Url.length === 0) return new Uint8Array(0);
    const padLen = (4 - (base64Url.length % 4)) % 4;
    const padded =
        base64Url.replace(/-/g, "+").replace(/_/g, "/") + "=".repeat(padLen);
    const binary = atob(padded);
    const out = new Uint8Array(binary.length);
    for (let i = 0; i < binary.length; i += 1) {
        out[i] = binary.charCodeAt(i);
    }
    return out;
}

/** Encode raw bytes as base64-url-no-pad. */
function encodeBase64Url(bytes: Uint8Array): string {
    const codes: number[] = [];
    for (const byte of bytes) {
        codes.push(byte);
    }
    const binary = String.fromCharCode(...codes);
    const b64 = btoa(binary);
    return b64.replace(/\+/g, "-").replace(/\//g, "_").replace(/=+$/g, "");
}

function textToBytes(text: string): Uint8Array {
    return new TextEncoder().encode(text);
}

function bytesToText(bytes: Uint8Array): string {
    return new TextDecoder().decode(bytes);
}