import { access, readFile, realpath } from "node:fs/promises";
import { constants } from "node:fs";
import { dirname, join, parse, resolve } from "node:path";
import { z } from "zod";

const dockerCommand = ["docker", "run", "-i", "--rm", "--init", "mcr.microsoft.com/playwright/mcp"];
const directPackageManifest = z.object({
    name: z.literal("@playwright/mcp"),
    bin: z.string(),
});
const namedPackageManifest = z.object({
    name: z.literal("@playwright/mcp"),
    bin: z.object({ "playwright-mcp": z.string() }),
});
const playwrightPackageManifest = z.object({
    name: z.literal("playwright"),
    bin: z.object({ playwright: z.string() }),
});
const playwrightTestPackageManifest = z.object({
    name: z.literal("@playwright/test"),
    bin: z.object({ playwright: z.string() }),
    dependencies: z.object({ playwright: z.string() }),
});

async function packageExecutable(packageRoot: string) {
    try {
        const input = JSON.parse(await readFile(join(packageRoot, "package.json"), "utf8"));
        const direct = directPackageManifest.safeParse(input);
        const bin = direct.success
            ? direct.data.bin
            : namedPackageManifest.parse(input).bin["playwright-mcp"];
        const executable = resolve(packageRoot, bin);
        await access(executable, constants.X_OK);
        return executable;
    } catch {
        return;
    }
}

async function ordinaryPackageExecutable(packageRoot: string) {
    try {
        const manifest = playwrightPackageManifest.parse(
            JSON.parse(await readFile(join(packageRoot, "package.json"), "utf8")),
        );
        const executable = resolve(packageRoot, manifest.bin.playwright);
        await access(executable, constants.X_OK);
        return executable;
    } catch {
        return;
    }
}

async function playwrightDependency(packageRoot: string) {
    let current = await realpath(packageRoot);
    const root = parse(current).root;
    while (true) {
        const executable = await ordinaryPackageExecutable(
            join(current, "node_modules/playwright"),
        );
        if (executable) return executable;
        if (current === root) return;
        current = dirname(current);
    }
}

async function testPackageExecutable(packageRoot: string) {
    try {
        const manifest = playwrightTestPackageManifest.parse(
            JSON.parse(await readFile(join(packageRoot, "package.json"), "utf8")),
        );
        if (!(await playwrightDependency(packageRoot))) return;
        const executable = resolve(packageRoot, manifest.bin.playwright);
        await access(executable, constants.X_OK);
        return executable;
    } catch {
        return;
    }
}

async function verifiedPathExecutable(candidate: string, kind: "mcp" | "playwright") {
    try {
        await access(candidate, constants.X_OK);
        const target = await realpath(candidate);
        let directory = dirname(target);
        const root = parse(directory).root;
        while (true) {
            const executable =
                kind === "mcp"
                    ? await packageExecutable(directory)
                    : ((await ordinaryPackageExecutable(directory)) ??
                      (await testPackageExecutable(directory)));
            if (executable && (await realpath(executable)) === target) return candidate;
            if (directory === root) return;
            directory = dirname(directory);
        }
    } catch {
        return;
    }
}

export async function playwrightMcpCommand(
    directory: string,
    path = process.env.PATH ?? "",
): Promise<string[]> {
    let current = resolve(directory);
    const root = parse(current).root;
    while (true) {
        const executable = await packageExecutable(join(current, "node_modules/@playwright/mcp"));
        if (executable) return [executable];
        if (current === root) break;
        current = dirname(current);
    }

    for (const entry of path.split(process.platform === "win32" ? ";" : ":")) {
        if (!entry) continue;
        const executable = await verifiedPathExecutable(join(entry, "playwright-mcp"), "mcp");
        if (executable) return [executable];
    }

    current = resolve(directory);
    while (true) {
        const playwright = await ordinaryPackageExecutable(
            join(current, "node_modules/playwright"),
        );
        const test = await testPackageExecutable(join(current, "node_modules/@playwright/test"));
        if (playwright || test) return ["npx", "-y", "@playwright/mcp@latest"];
        if (current === root) break;
        current = dirname(current);
    }

    for (const entry of path.split(process.platform === "win32" ? ";" : ":")) {
        if (!entry) continue;
        const executable = await verifiedPathExecutable(join(entry, "playwright"), "playwright");
        if (executable) return ["npx", "-y", "@playwright/mcp@latest"];
    }
    return [...dockerCommand];
}