import { exec, spawn, ExecException } from "child_process";
import * as vscode from "vscode";
import { getGitDiff, getRepositoryRoot } from "./gitService";
import { output } from "./extension";

export interface GenerateOptions {
    model?: string;
}

let opencodeAvailableCache: boolean | null = null;

const DEFAULT_PROMPT = `You are a helpful assistant that generates git commit messages.
Generate a concise Conventional Commit message (max 72 characters for the subject line).
Format: <type>(<scope>): <description>

Types: feat, fix, refactor, docs, style, test, chore, perf, ci, build, revert

Only output the commit message, nothing else.`;

export async function isOpenCodeAvailable(): Promise<boolean> {
    if (opencodeAvailableCache !== null) {
        return opencodeAvailableCache;
    }
    return new Promise((resolve) => {
        exec("which opencode", (error: ExecException | null) => {
            opencodeAvailableCache = !error;
            resolve(opencodeAvailableCache);
        });
    });
}

export async function generateCommitMessage(
    options: GenerateOptions = {},
): Promise<string> {
    const opencodeAvailable = await isOpenCodeAvailable();
    if (!opencodeAvailable) {
        throw new Error(
            "OpenCode is not installed. Please install it from https://opencode.ai",
        );
    }

    const [diff, repoRoot] = await Promise.all([
        getGitDiff(),
        getRepositoryRoot(),
    ]);

    const config = vscode.workspace.getConfiguration("aiCommitExt");
    const model = options.model || config.get<string>("model", "");

    const prompt = `${DEFAULT_PROMPT}

Here are the git changes:
${diff}

Generate a concise Conventional Commit message for these changes:`;

    const log = `[${Date.now()}]\r\n${prompt}`;
    output.appendLine(log);

    return new Promise((resolve, reject) => {
        const args: string[] = [
            "run",
            "--format",
            "default",
            "--variant",
            "minimal",
        ];

        if (model) {
            args.push("--model", model);
        }

        const proc = spawn("opencode", args, {
            stdio: ["pipe", "pipe", "pipe"],
            shell: false,
            cwd: repoRoot || undefined,
        });

        let stdout = "";
        let stderr = "";

        proc.stdout.on("data", (data: Buffer) => {
            stdout += data.toString();
        });
        proc.stderr.on("data", (data: Buffer) => {
            stderr += data.toString();
        });
        proc.stdin?.write(prompt + "\n", (err) => {
            if (err) {
                new Error(`OpenCode write error with ${err}`);
            }
            proc.stdin?.end();
        });

        proc.on("close", (code: number | null) => {
            if (code !== 0) {
                reject(
                    new Error(`OpenCode exited with code ${code}: ${stderr}`),
                );
                return;
            }

            const message = parseCommitMessage(stdout);
            resolve(message);
        });

        proc.on("error", (err: Error) => {
            reject(new Error(`Failed to run opencode: ${err.message}`));
        });

        setTimeout(() => {
            proc.kill();
            reject(new Error("OpenCode timed out"));
        }, 120000);
    });
}

function parseCommitMessage(output: string): string {
    const lines = output.split("\n").filter((line) => line.trim());

    for (const line of lines) {
        const trimmed = line.trim();

        if (
            trimmed.includes(":") &&
            (trimmed.startsWith("feat") ||
                trimmed.startsWith("fix") ||
                trimmed.startsWith("refactor") ||
                trimmed.startsWith("docs") ||
                trimmed.startsWith("style") ||
                trimmed.startsWith("test") ||
                trimmed.startsWith("chore") ||
                trimmed.startsWith("perf") ||
                trimmed.startsWith("ci") ||
                trimmed.startsWith("build") ||
                trimmed.startsWith("revert"))
        ) {
            return trimmed.substring(0, 200);
        }
    }

    const cleaned =
        output.trim().split("\n")[0]?.substring(0, 200) ||
        "chore: generated commit message";
    return cleaned;
}