using System.Diagnostics;
using System.Globalization;
using ClaudeDo.Data.Environment;
using ClaudeDo.Worker.Usage.TokenTracker.Interfaces;

namespace ClaudeDo.Worker.Usage.TokenTracker;

/// <summary>
/// Starts the TokenTracker CLI. Resolution goes through <see cref="ExecutableResolver"/> because
/// an npm-installed CLI is a <c>.cmd</c> shim, which <c>UseShellExecute = false</c> cannot exec
/// directly. We deliberately never fall back to <c>npx</c> — that would silently download a
/// package behind the user's back.
/// </summary>
public sealed class TokenTrackerClient : ITokenTrackerClient
{
    private static readonly TimeSpan ExportTimeout = TimeSpan.FromSeconds(120);
    private static readonly TimeSpan ProbeTimeout = TimeSpan.FromSeconds(20);
    private static readonly TimeSpan InstallTimeout = TimeSpan.FromMinutes(5);
    private const int MinimumNodeMajor = 20;

    public async Task<TokenTrackerProbe> ProbeAsync(CancellationToken ct = default)
    {
        var node = await RunAsync("node", ["--version"], ProbeTimeout, null, ct);
        var nodeVersion = node.Ok ? node.StdOut.Trim() : null;
        var nodeOk = NodeMajor(nodeVersion) >= MinimumNodeMajor;

        var cli = await RunAsync(TokenTrackerArgs.Command, TokenTrackerArgs.Version(), ProbeTimeout, null, ct);
        return cli.Ok
            ? new TokenTrackerProbe(true, cli.StdOut.Trim(), nodeOk, nodeVersion, null)
            : new TokenTrackerProbe(false, null, nodeOk, nodeVersion, cli.Error);
    }

    public Task<TokenTrackerRunResult> ExportAsync(DateOnly from, DateOnly to, CancellationToken ct = default) =>
        RunAsync(TokenTrackerArgs.Command, TokenTrackerArgs.Export(from, to), ExportTimeout, null, ct);

    public Task<TokenTrackerRunResult> InstallAsync(IProgress<string>? output = null, CancellationToken ct = default) =>
        RunAsync(TokenTrackerArgs.NpmCommand, TokenTrackerArgs.Install(), InstallTimeout, output, ct);

    /// <summary>Visible for the probe's version parsing; returns 0 when unreadable.</summary>
    internal static int NodeMajor(string? version)
    {
        if (string.IsNullOrWhiteSpace(version)) return 0;

        var trimmed = version.Trim().TrimStart('v', 'V');
        var major = trimmed.Split('.', 2)[0];
        return int.TryParse(major, NumberStyles.Integer, CultureInfo.InvariantCulture, out var v) ? v : 0;
    }

    private static async Task<TokenTrackerRunResult> RunAsync(
        string command,
        IReadOnlyList<string> arguments,
        TimeSpan timeout,
        IProgress<string>? output,
        CancellationToken ct)
    {
        var resolved = ExecutableResolver.Resolve(command);
        if (resolved is null)
            return new TokenTrackerRunResult(false, "", $"'{command}' not found on PATH.");

        var startInfo = new ProcessStartInfo
        {
            RedirectStandardOutput = true,
            RedirectStandardError = true,
            UseShellExecute = false,
            CreateNoWindow = true,
        };

        if (resolved.IsShim)
        {
            var shim = ExecutableResolver.BuildShimStartInfo(resolved.Path, arguments);
            startInfo.FileName = shim.FileName;
            startInfo.Arguments = shim.Arguments;
        }
        else
        {
            startInfo.FileName = resolved.Path;
            foreach (var arg in arguments) startInfo.ArgumentList.Add(arg);
        }

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

        try
        {
            using var process = Process.Start(startInfo);
            if (process is null)
                return new TokenTrackerRunResult(false, "", $"Could not start '{command}'.");

            // Both pipes are drained concurrently — reading one to the end first deadlocks as
            // soon as the other fills its buffer, and a full-history export is ~1 MB of stdout.
            var stdoutTask = process.StandardOutput.ReadToEndAsync(timeoutCts.Token);
            var stderrTask = ReadLinesAsync(process, output, timeoutCts.Token);

            await process.WaitForExitAsync(timeoutCts.Token);
            var stdout = await stdoutTask;
            var stderr = await stderrTask;

            return process.ExitCode == 0
                ? new TokenTrackerRunResult(true, stdout, null)
                : new TokenTrackerRunResult(false, stdout,
                    $"'{command}' exited with code {process.ExitCode}. {Head(stderr)}".TrimEnd());
        }
        catch (OperationCanceledException) when (!ct.IsCancellationRequested)
        {
            return new TokenTrackerRunResult(false, "", $"'{command}' timed out after {timeout.TotalSeconds:0}s.");
        }
        catch (Exception ex)
        {
            return new TokenTrackerRunResult(false, "", $"'{command}' failed: {ex.Message}");
        }
    }

    private static async Task<string> ReadLinesAsync(Process process, IProgress<string>? output, CancellationToken ct)
    {
        var lines = new List<string>();
        while (await process.StandardError.ReadLineAsync(ct) is { } line)
        {
            lines.Add(line);
            output?.Report(line);
        }
        return string.Join(System.Environment.NewLine, lines);
    }

    private static string Head(string text)
    {
        var trimmed = text.Trim();
        return trimmed.Length <= 300 ? trimmed : trimmed[..300] + "…";
    }
}