using System.Diagnostics;
using Microsoft.AspNetCore.Hosting;

namespace w4c_workflows.Services;

// Git transport half of the Forgejo workflow repo service: bounded-timeout
// process execution, origin reconciliation and local-config cleanup. The admin
// HTTP API lives in ForgejoWorkflowRepoService.AdminApi.cs; the repo/clone
// lifecycle lives in ForgejoWorkflowRepoService.cs.

public sealed partial class ForgejoWorkflowRepoService
{
    /// <summary>
    /// Runs git and returns its stdout on success / stderr on failure (null when
    /// git could not be run at all). Callers that must distinguish success from
    /// failure reliably should use <see cref="RunGitExitAsync"/> and check the
    /// exit code instead of scanning the output text.
    /// </summary>
    private async Task<string?> RunGitAsync(string workDir, CancellationToken ct, params string[] args)
    {
        var result = await RunGitExitAsync(workDir, ct, args);
        if (result == null)
            return null;
        return result.Value.ExitCode == 0 ? result.Value.Stdout : result.Value.Stderr;
    }

    /// <summary>
    /// Runs git with a hard wall-clock timeout and returns the real exit code plus
    /// separately captured stdout/stderr. Default git has no connect/transfer
    /// timeout, so a dead or unreachable remote (e.g. a stale Forgejo base URL
    /// after the server moved) would otherwise block the calling request forever.
    /// On timeout the whole process tree is killed and null is returned.
    /// </summary>
    private async Task<(int ExitCode, string Stdout, string Stderr)?> RunGitExitAsync(
        string workDir, CancellationToken ct, params string[] args)
    {
        try
        {
            var psi = new ProcessStartInfo("git")
            {
                WorkingDirectory = workDir,
                RedirectStandardOutput = true,
                RedirectStandardError = true,
                UseShellExecute = false,
                CreateNoWindow = true,
            };
            foreach (var a in args) psi.ArgumentList.Add(a);

            using var process = Process.Start(psi);
            if (process == null) return null;

            using var timeout = CancellationTokenSource.CreateLinkedTokenSource(ct);
            timeout.CancelAfter(GitOperationTimeout);

            var stdoutTask = process.StandardOutput.ReadToEndAsync();
            var stderrTask = process.StandardError.ReadToEndAsync();

            try
            {
                await process.WaitForExitAsync(timeout.Token);
            }
            catch (OperationCanceledException)
            {
                // Timed out (or the request was aborted) — kill the process tree so a
                // hung git transport can't leak or keep a subsequent request blocked.
                TryKill(process);
                return null;
            }

            return (process.ExitCode, await stdoutTask, await stderrTask);
        }
        catch (Exception ex)
        {
            _logger.LogDebug(ex, "git invocation failed in {Dir}", workDir);
            return null;
        }
    }

    /// <summary>
    /// Ensures the clone's remote `origin` points at the currently-configured Forgejo
    /// base. Used when a clone already exists but may have been created against an old
    /// Forgejo location (e.g. forgejo.wiz4chat.com → localhost). A stale origin makes
    /// `git pull` hang against a dead host. Best-effort and non-blocking on failure.
    /// </summary>
    private async Task ReconcileOriginAsync(string tenantDir, string login, string? repoName, CancellationToken ct)
    {
        var fullName = RepoFullNameForLogin(login, repoName);
        var desired = $"{_forgejoBase}/{fullName}.git";

        try
        {
            var current = await RunGitAsync(tenantDir, ct, "remote", "get-url", "origin");
            if (string.IsNullOrWhiteSpace(current))
                return;
            current = current.Trim();
            if (current.Equals(desired, StringComparison.OrdinalIgnoreCase))
                return;

            _logger.LogInformation(
                "Reconciling workflow repo origin {Dir}: {Current} -> {Desired}",
                tenantDir, current, desired);
            await RunGitAsync(tenantDir, ct, "remote", "set-url", "origin", desired);
        }
        catch (Exception ex)
        {
            _logger.LogDebug(ex, "Could not reconcile origin for {Dir}", tenantDir);
        }
    }

    private static void TryKill(Process process)
    {
        try
        {
            if (!process.HasExited)
                process.Kill(entireProcessTree: true);
        }
        catch
        {
            // Best-effort cleanup.
        }
    }

    private static void UnsetLocalConfig(string repoRoot, string key)
    {
        try
        {
            var psi = new ProcessStartInfo("git")
            {
                WorkingDirectory = repoRoot,
                RedirectStandardOutput = true,
                RedirectStandardError = true,
                UseShellExecute = false,
                CreateNoWindow = true,
            };
            psi.ArgumentList.Add("config");
            psi.ArgumentList.Add("--local");
            psi.ArgumentList.Add("--unset");
            psi.ArgumentList.Add(key);
            using var p = Process.Start(psi);
            p?.WaitForExit(3000);
        }
        catch
        {
            // Best-effort cleanup.
        }
    }
}