using ClaudeDo.Data;
using ClaudeDo.Data.Git;
using ClaudeDo.Data.Models;
using ClaudeDo.Data.Repositories;
using ClaudeDo.Worker.Hub;
using Microsoft.EntityFrameworkCore;
using TaskStatus = ClaudeDo.Data.Models.TaskStatus;

namespace ClaudeDo.Worker.Services;

public sealed record MergeResult(
    string Status,
    IReadOnlyList<string> ConflictFiles,
    string? ErrorMessage);

public sealed record MergeTargets(
    string DefaultBranch,
    IReadOnlyList<string> LocalBranches);

public sealed class TaskMergeService
{
    public const string StatusMerged   = "merged";
    public const string StatusConflict = "conflict";
    public const string StatusBlocked  = "blocked";

    private readonly IDbContextFactory<ClaudeDoDbContext> _dbFactory;
    private readonly GitService _git;
    private readonly HubBroadcaster _broadcaster;
    private readonly ILogger<TaskMergeService> _logger;

    public TaskMergeService(
        IDbContextFactory<ClaudeDoDbContext> dbFactory,
        GitService git,
        HubBroadcaster broadcaster,
        ILogger<TaskMergeService> logger)
    {
        _dbFactory = dbFactory;
        _git = git;
        _broadcaster = broadcaster;
        _logger = logger;
    }

    public async Task<MergeResult> MergeAsync(
        string taskId,
        string targetBranch,
        bool removeWorktree,
        string commitMessage,
        CancellationToken ct)
    {
        TaskEntity task;
        ListEntity list;
        WorktreeEntity? wt;

        using (var ctx = _dbFactory.CreateDbContext())
        {
            task = await new TaskRepository(ctx).GetByIdAsync(taskId, ct)
                ?? throw new KeyNotFoundException($"Task '{taskId}' not found.");
            list = await new ListRepository(ctx).GetByIdAsync(task.ListId, ct)
                ?? throw new InvalidOperationException("List not found.");
            wt = await new WorktreeRepository(ctx).GetByTaskIdAsync(taskId, ct);
        }

        if (task.Status == TaskStatus.Running)
            return Blocked("task is running");
        if (wt is null)
            return Blocked("task has no worktree");
        if (wt.State != WorktreeState.Active)
            return Blocked($"worktree state is {wt.State}");
        if (string.IsNullOrWhiteSpace(list.WorkingDir))
            return Blocked("list has no working directory");
        if (!await _git.IsGitRepoAsync(list.WorkingDir, ct))
            return Blocked("working directory is not a git repository");
        if (await _git.IsMidMergeAsync(list.WorkingDir, ct))
            return Blocked("target working directory is mid-merge");
        if (await _git.HasChangesAsync(list.WorkingDir, ct))
            return Blocked("target working tree has uncommitted changes");

        var currentBranch = await _git.GetCurrentBranchAsync(list.WorkingDir, ct);
        if (!string.Equals(currentBranch, targetBranch, StringComparison.Ordinal))
        {
            try { await _git.CheckoutBranchAsync(list.WorkingDir, targetBranch, ct); }
            catch (Exception ex) { return Blocked($"failed to switch target branch: {ex.Message}"); }
        }

        var (exitCode, stderr) = await _git.MergeNoFfAsync(list.WorkingDir, wt.BranchName, commitMessage, ct);
        if (exitCode != 0)
        {
            List<string> files;
            try { files = await _git.ListConflictedFilesAsync(list.WorkingDir, ct); }
            catch { files = new(); }

            // If abort fails the repo is left mid-merge; the caller must resolve manually.
            // Return Blocked (not conflict) so the UI does not offer a stale conflict list.
            try { await _git.MergeAbortAsync(list.WorkingDir, ct); }
            catch (Exception ex)
            {
                _logger.LogError(ex, "git merge --abort failed after conflict — repo is mid-merge");
                return Blocked($"merge conflict and abort failed: {ex.Message} — repo is mid-merge, resolve manually");
            }

            if (files.Count == 0)
            {
                // Non-conflict failure (e.g. unrelated histories).
                return new MergeResult(StatusBlocked, Array.Empty<string>(), $"merge failed: {stderr}");
            }

            return new MergeResult(StatusConflict, files, null);
        }

        string? cleanupWarning = null;
        if (removeWorktree)
        {
            try
            {
                await _git.WorktreeRemoveAsync(list.WorkingDir, wt.Path, force: false, ct);
                try { await _git.BranchDeleteAsync(list.WorkingDir, wt.BranchName, force: false, ct); }
                catch (Exception ex)
                {
                    _logger.LogWarning(ex, "branch delete failed for {Branch}", wt.BranchName);
                    cleanupWarning = $"worktree removed, branch delete failed: {ex.Message}";
                }
            }
            catch (Exception ex)
            {
                _logger.LogWarning(ex, "worktree remove failed for {Path}", wt.Path);
                cleanupWarning = $"worktree remove failed: {ex.Message}";
            }
        }

        using (var ctx = _dbFactory.CreateDbContext())
        {
            await new WorktreeRepository(ctx).SetStateAsync(taskId, WorktreeState.Merged, ct);
        }
        await _broadcaster.WorktreeUpdated(taskId);

        _logger.LogInformation(
            "Merged task {TaskId} branch {Branch} into {Target} (remove worktree: {Remove})",
            taskId, wt.BranchName, targetBranch, removeWorktree);
        await _broadcaster.WorkerLog($"Merged \"{task.Title}\" into {targetBranch}", WorkerLogLevel.Success, DateTime.UtcNow);

        return new MergeResult(StatusMerged, Array.Empty<string>(), cleanupWarning);
    }

    public async Task<MergeTargets> GetTargetsAsync(string taskId, CancellationToken ct)
    {
        TaskEntity task;
        ListEntity list;
        using (var ctx = _dbFactory.CreateDbContext())
        {
            task = await new TaskRepository(ctx).GetByIdAsync(taskId, ct)
                ?? throw new KeyNotFoundException($"Task '{taskId}' not found.");
            list = await new ListRepository(ctx).GetByIdAsync(task.ListId, ct)
                ?? throw new InvalidOperationException("List not found.");
        }

        if (string.IsNullOrWhiteSpace(list.WorkingDir))
            return new MergeTargets("", Array.Empty<string>());

        var current  = await _git.GetCurrentBranchAsync(list.WorkingDir, ct);
        var branches = await _git.ListLocalBranchesAsync(list.WorkingDir, ct);
        return new MergeTargets(current, branches);
    }

    private static MergeResult Blocked(string reason) =>
        new(StatusBlocked, Array.Empty<string>(), reason);
}