using System.Text.Json;
using ControlPlane.Core.Models;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Logging;

namespace ControlPlane.Core.Services;

/// <summary>
/// Persists build and release history to JSON files in the ClientAssets folder.
/// Thread-safe — all writes go through a single lock per file.
/// </summary>
public class BuildHistoryService
{
    private readonly string _buildsPath;
    private readonly string _releasesPath;
    private readonly ILogger<BuildHistoryService> _logger;

    private static readonly SemaphoreSlim _buildLock   = new(1, 1);
    private static readonly SemaphoreSlim _releaseLock = new(1, 1);

    private static readonly JsonSerializerOptions JsonOpts = new()
    {
        WriteIndented          = true,
        PropertyNamingPolicy   = JsonNamingPolicy.CamelCase,
        Converters             = { new System.Text.Json.Serialization.JsonStringEnumConverter() },
    };

    public BuildHistoryService(IConfiguration config, ILogger<BuildHistoryService> logger)
    {
        var folder = config["ClientAssets__Folder"] ?? config["ClientAssets:Folder"]
                     ?? Path.GetFullPath(Path.Combine(AppContext.BaseDirectory, "..", "ClientAssets"));
        Directory.CreateDirectory(folder);
        _buildsPath   = Path.Combine(folder, "builds.json");
        _releasesPath = Path.Combine(folder, "releases.json");
        _logger = logger;
    }

    // ── Builds ──────────────────────────────────────────────────────────────

    public async Task<BuildRecord> CreateBuildAsync(BuildKind kind, string target)
    {
        var record = new BuildRecord { Kind = kind, Target = target };
        await SaveBuildAsync(record);
        return record;
    }

    public async Task CompleteBuildAsync(BuildRecord record, BuildStatus status, string? digest = null)
    {
        record.Status      = status;
        record.FinishedAt  = DateTimeOffset.UtcNow;
        record.DurationMs  = (int)(record.FinishedAt.Value - record.StartedAt).TotalMilliseconds;
        record.ImageDigest = digest;
        await SaveBuildAsync(record);
    }

    public async Task AppendBuildLogAsync(BuildRecord record, string line)
    {
        record.Log.Add(line);
        // Flush to disk every 20 lines to avoid excessive I/O but keep reasonable freshness
        if (record.Log.Count % 20 == 0)
            await SaveBuildAsync(record);
    }

    public async Task<List<BuildRecord>> GetBuildsAsync()
    {
        await _buildLock.WaitAsync();
        try   { return LoadJson<BuildRecord>(_buildsPath); }
        finally { _buildLock.Release(); }
    }

    private async Task SaveBuildAsync(BuildRecord record)
    {
        await _buildLock.WaitAsync();
        try
        {
            var all = LoadJson<BuildRecord>(_buildsPath);
            var idx = all.FindIndex(b => b.Id == record.Id);
            if (idx >= 0) all[idx] = record;
            else          all.Insert(0, record);

            // Keep last 100 builds
            if (all.Count > 100) all = all[..100];
            await File.WriteAllTextAsync(_buildsPath, JsonSerializer.Serialize(all, JsonOpts));
        }
        finally { _buildLock.Release(); }
    }

    // ── Releases ────────────────────────────────────────────────────────────

    public async Task<ReleaseRecord> CreateReleaseAsync(string environment, string imageName)
    {
        var record = new ReleaseRecord { Environment = environment, ImageName = imageName };
        await SaveReleaseAsync(record);
        return record;
    }

    public async Task UpdateReleaseAsync(ReleaseRecord record)
    {
        record.FinishedAt = DateTimeOffset.UtcNow;
        await SaveReleaseAsync(record);
    }

    public async Task<List<ReleaseRecord>> GetReleasesAsync()
    {
        await _releaseLock.WaitAsync();
        try   { return LoadJson<ReleaseRecord>(_releasesPath); }
        finally { _releaseLock.Release(); }
    }

    private async Task SaveReleaseAsync(ReleaseRecord record)
    {
        await _releaseLock.WaitAsync();
        try
        {
            var all = LoadJson<ReleaseRecord>(_releasesPath);
            var idx = all.FindIndex(r => r.Id == record.Id);
            if (idx >= 0) all[idx] = record;
            else          all.Insert(0, record);

            if (all.Count > 50) all = all[..50];
            await File.WriteAllTextAsync(_releasesPath, JsonSerializer.Serialize(all, JsonOpts));
        }
        finally { _releaseLock.Release(); }
    }

    // ── Helpers ─────────────────────────────────────────────────────────────

    private static List<T> LoadJson<T>(string path)
    {
        if (!File.Exists(path)) return [];
        try
        {
            var json = File.ReadAllText(path);
            return JsonSerializer.Deserialize<List<T>>(json, JsonOpts) ?? [];
        }
        catch { return []; }
    }
}