using System.Text.Json;
using ClaudeDo.Data;
using ClaudeDo.Data.Models;
using ClaudeDo.Data.Repositories;
using ClaudeDo.Worker.Config;
using ClaudeDo.Worker.Hub;
using ClaudeDo.Worker.State;
using Microsoft.EntityFrameworkCore;
using TaskStatus = ClaudeDo.Data.Models.TaskStatus;

namespace ClaudeDo.Worker.Runner;

public sealed class TaskRunner
{
    private readonly IClaudeProcess _claude;
    private readonly IDbContextFactory<ClaudeDoDbContext> _dbFactory;
    private readonly HubBroadcaster _broadcaster;
    private readonly WorktreeManager _wtManager;
    private readonly ClaudeArgsBuilder _argsBuilder;
    private readonly WorkerConfig _cfg;
    private readonly ILogger<TaskRunner> _logger;
    private readonly ITaskStateService _state;
    private readonly TaskRunTokenRegistry _tokens;

    public TaskRunner(
        IClaudeProcess claude,
        IDbContextFactory<ClaudeDoDbContext> dbFactory,
        HubBroadcaster broadcaster,
        WorktreeManager wtManager,
        ClaudeArgsBuilder argsBuilder,
        WorkerConfig cfg,
        ILogger<TaskRunner> logger,
        ITaskStateService state,
        TaskRunTokenRegistry tokens)
    {
        _claude = claude;
        _dbFactory = dbFactory;
        _broadcaster = broadcaster;
        _wtManager = wtManager;
        _argsBuilder = argsBuilder;
        _cfg = cfg;
        _logger = logger;
        _state = state;
        _tokens = tokens;
    }

    public async Task RunAsync(TaskEntity task, string slot, CancellationToken ct)
    {
        string? mcpToken = null;
        string? mcpConfigPath = null;
        try
        {
            ListEntity? list;
            ListConfigEntity? listConfig;
            List<SubtaskEntity> subtasks;

            using (var context = _dbFactory.CreateDbContext())
            {
                var listRepo = new ListRepository(context);
                list = await listRepo.GetByIdAsync(task.ListId, ct);
                if (list is null)
                {
                    await MarkFailed(task.Id, task.Title, slot, "List not found.");
                    return;
                }
                listConfig = await listRepo.GetConfigAsync(task.ListId, ct);

                var subtaskRepo = new SubtaskRepository(context);
                subtasks = await subtaskRepo.GetByTaskIdAsync(task.Id, ct);
            }

            // Determine working directory: worktree or sandbox.
            var prep = await PrepareRunDirectoryAsync(task, list, ct);
            if (prep.FailureReason is not null)
            {
                await MarkFailed(task.Id, task.Title, slot, prep.FailureReason);
                return;
            }
            var wtCtx = prep.WtCtx;
            var runDir = prep.RunDir!;

            var resolvedConfig = await ResolveConfigAsync(task, listConfig, null, ct);

            // Improvement-eligible runs get a per-run MCP identity so the agent can file
            // out-of-scope follow-ups via SuggestImprovement. Children and planning runs do not.
            if (task.ParentTaskId is null && task.PlanningPhase == PlanningPhase.None)
            {
                mcpToken = TaskRunTokenRegistry.GenerateToken();
                _tokens.Register(mcpToken, task.Id);
                Directory.CreateDirectory(_cfg.LogRoot);
                mcpConfigPath = Path.Combine(_cfg.LogRoot, $"{task.Id}_mcp.json");
                await File.WriteAllTextAsync(mcpConfigPath, BuildRunMcpConfigJson(mcpToken), ct);
                resolvedConfig = resolvedConfig with
                {
                    McpConfigPath = mcpConfigPath,
                    AllowedTools = "mcp__claudedo_run__SuggestImprovement",
                };
            }

            var now = DateTime.UtcNow;
            await _state.StartRunningAsync(task.Id, now, ct);
            await _broadcaster.TaskStarted(slot, task.Id, now);

            // Build prompt: title + description + only the OPEN sub-tasks (resolved ones are dropped).
            var prompt = TaskPromptComposer.Compose(
                task.Title, task.Description,
                subtasks.Select(s => (s.Title, s.Completed)));

            // Run 1.
            var result = await RunOnceAsync(task.Id, task.Title, slot, runDir, resolvedConfig, 1, false, prompt, ct);

            if (result.IsSuccess)
            {
                await HandleSuccess(task, list, slot, wtCtx, result, ct);
            }
            else
            {
                // Auto-retry: one attempt if we have a session ID.
                if (result.SessionId is not null)
                {
                    _logger.LogInformation("Auto-retrying task {TaskId} with session {SessionId}", task.Id, result.SessionId);
                    var retryConfig = resolvedConfig with { ResumeSessionId = result.SessionId };
                    var retryPrompt = BuildRetryPrompt(result.ErrorMarkdown);

                    var retryResult = await RunOnceAsync(task.Id, task.Title, slot, runDir, retryConfig, 2, true, retryPrompt, ct);

                    if (retryResult.IsSuccess)
                    {
                        await HandleSuccess(task, list, slot, wtCtx, retryResult, ct);
                    }
                    else
                    {
                        await MarkFailed(task.Id, task.Title, slot, retryResult.ErrorMarkdown, retryResult.TurnCount);
                    }
                }
                else
                {
                    await MarkFailed(task.Id, task.Title, slot, result.ErrorMarkdown, result.TurnCount);
                }
            }

            await _broadcaster.TaskUpdated(task.Id);
        }
        catch (OperationCanceledException)
        {
            _logger.LogInformation("Task {TaskId} was cancelled", task.Id);
            await MarkFailed(task.Id, task.Title, slot, "Task cancelled.");
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Unhandled exception running task {TaskId}", task.Id);
            await MarkFailed(task.Id, task.Title, slot, $"Unhandled error: {ex.Message}");
        }
        finally
        {
            if (mcpToken is not null)
            {
                _tokens.Unregister(mcpToken);
                if (mcpConfigPath is not null)
                    try { File.Delete(mcpConfigPath); } catch { /* best effort */ }
            }
        }
    }

    public async Task ContinueAsync(string taskId, string followUpPrompt, string slot, CancellationToken ct)
    {
        TaskEntity task;
        TaskRunEntity lastRun;
        ListEntity list;
        ListConfigEntity? listConfig;
        WorktreeEntity? worktree;

        using (var context = _dbFactory.CreateDbContext())
        {
            var taskRepo = new TaskRepository(context);
            task = await taskRepo.GetByIdAsync(taskId, ct)
                ?? throw new KeyNotFoundException($"Task '{taskId}' not found.");

            var runRepo = new TaskRunRepository(context);
            lastRun = await runRepo.GetLatestByTaskIdAsync(taskId, ct)
                ?? throw new InvalidOperationException("No previous run to continue.");

            if (lastRun.SessionId is null)
                throw new InvalidOperationException("Previous run has no session ID — cannot resume.");

            var listRepo = new ListRepository(context);
            list = await listRepo.GetByIdAsync(task.ListId, ct)
                ?? throw new InvalidOperationException("List not found.");
            listConfig = await listRepo.GetConfigAsync(task.ListId, ct);

            var wtRepo = new WorktreeRepository(context);
            worktree = await wtRepo.GetByTaskIdAsync(taskId, ct);
        }

        var resolvedConfig = await ResolveConfigAsync(task, listConfig, lastRun.SessionId, ct);

        // Determine run directory from existing worktree or sandbox.
        string runDir;
        WorktreeContext? wtCtx = null;
        if (worktree is not null)
        {
            runDir = worktree.Path;
            wtCtx = new WorktreeContext(worktree.Path, worktree.BranchName, worktree.BaseCommit);
        }
        else
        {
            runDir = Path.Combine(_cfg.SandboxRoot, taskId);
        }

        var now = DateTime.UtcNow;
        await _state.StartRunningAsync(taskId, now, ct);
        await _broadcaster.TaskStarted(slot, taskId, now);

        var nextRunNumber = lastRun.RunNumber + 1;
        var result = await RunOnceAsync(taskId, task.Title, slot, runDir, resolvedConfig, nextRunNumber, false, followUpPrompt, ct);

        if (result.IsSuccess)
        {
            await HandleSuccess(task, list, slot, wtCtx, result, ct);
        }
        else
        {
            await MarkFailed(taskId, task.Title, slot, result.ErrorMarkdown, result.TurnCount);
        }

        await _broadcaster.TaskUpdated(taskId);
    }

    private readonly record struct RunDirResult(string? RunDir, WorktreeContext? WtCtx, string? FailureReason);

    private async Task<RunDirResult> PrepareRunDirectoryAsync(TaskEntity task, ListEntity list, CancellationToken ct)
    {
        if (list.WorkingDir is not null)
        {
            try
            {
                var wtCtx = await _wtManager.CreateAsync(task, list, ct);
                await _broadcaster.WorkerLog($"Created worktree for \"{task.Title}\"", WorkerLogLevel.Info, DateTime.UtcNow);
                return new RunDirResult(wtCtx.WorktreePath, wtCtx, null);
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "Failed to create worktree for task {TaskId}", task.Id);
                return new RunDirResult(null, null, $"Worktree creation failed: {ex.Message}");
            }
        }

        var sandboxDir = Path.Combine(_cfg.SandboxRoot, task.Id);
        Directory.CreateDirectory(sandboxDir);
        return new RunDirResult(sandboxDir, null, null);
    }

    private async Task<RunResult> RunOnceAsync(
        string taskId, string taskTitle, string slot, string runDir, ClaudeRunConfig config,
        int runNumber, bool isRetry, string prompt, CancellationToken ct)
    {
        var runId = Guid.NewGuid().ToString();
        var logPath = Path.Combine(_cfg.LogRoot, $"{taskId}_run{runNumber}.ndjson");

        var run = new TaskRunEntity
        {
            Id = runId,
            TaskId = taskId,
            RunNumber = runNumber,
            IsRetry = isRetry,
            Prompt = prompt,
            LogPath = logPath,
            StartedAt = DateTime.UtcNow,
        };

        using (var context = _dbFactory.CreateDbContext())
        {
            var runRepo = new TaskRunRepository(context);
            await runRepo.AddAsync(run, ct);

            // Point the task at this run's log immediately so the UI can replay
            // live output when the user navigates away and back mid-run.
            var taskRepo = new TaskRepository(context);
            await taskRepo.SetLogPathAsync(taskId, logPath, ct);
        }

        await _broadcaster.RunCreated(taskId, runNumber, isRetry);

        var arguments = _argsBuilder.Build(config);

        await using var logWriter = new LogWriter(logPath);

        try
        {
            await _broadcaster.WorkerLog($"Started Claude for \"{taskTitle}\"", WorkerLogLevel.Info, DateTime.UtcNow);
            var result = await _claude.RunAsync(
                arguments,
                prompt,
                runDir,
                async line =>
                {
                    await logWriter.WriteLineAsync(line, ct);
                    await _broadcaster.TaskMessage(taskId, "[stdout] " + line);
                },
                ct);

            // Update the run record with results. Use CancellationToken.None:
            // this is a terminal write that must always complete, even if the
            // caller's token is already cancelled.
            run.SessionId = result.SessionId;
            run.ResultMarkdown = result.ResultMarkdown;
            run.StructuredOutputJson = result.StructuredOutputJson;
            run.ErrorMarkdown = result.ErrorMarkdown;
            run.ExitCode = result.ExitCode;
            run.TurnCount = result.TurnCount;
            run.TokensIn = result.TokensIn;
            run.TokensOut = result.TokensOut;
            run.FinishedAt = DateTime.UtcNow;

            using (var context = _dbFactory.CreateDbContext())
            {
                var runRepo = new TaskRunRepository(context);
                await runRepo.UpdateAsync(run, CancellationToken.None);
            }

            return result;
        }
        catch (OperationCanceledException)
        {
            // Ensure the run row is completed so ContinueAsync / inspection
            // isn't left staring at a null session_id / finished_at.
            run.ErrorMarkdown = "Cancelled.";
            run.ExitCode = -1;
            run.FinishedAt = DateTime.UtcNow;
            try
            {
                using var context = _dbFactory.CreateDbContext();
                var runRepo = new TaskRunRepository(context);
                await runRepo.UpdateAsync(run, CancellationToken.None);
            }
            catch (Exception updateEx)
            {
                _logger.LogError(updateEx, "Failed to finalize cancelled run {RunId} for task {TaskId}", runId, taskId);
            }
            throw;
        }
    }

    private async Task HandleSuccess(TaskEntity task, ListEntity list, string slot, WorktreeContext? wtCtx, RunResult result, CancellationToken ct)
    {
        if (wtCtx is not null)
        {
            var committed = await _wtManager.CommitIfChangedAsync(wtCtx, task, list, ct);
            if (committed)
            {
                await _broadcaster.WorkerLog($"Committed changes in \"{task.Title}\"", WorkerLogLevel.Info, DateTime.UtcNow);
                await _broadcaster.WorktreeUpdated(task.Id);
            }
        }

        // Terminal DB write uses CancellationToken.None so the task status
        // is never left as 'running' because of a cancel that arrived
        // after the Claude run already succeeded.
        // Standalone tasks gate on review; planning children go straight to Done
        // so the sequential chain (which advances on terminal states) is unaffected.
        // Planning parents (PlanningPhase != None) are containers, not reviewable work.
        var finishedAt = DateTime.UtcNow;
        using (var ctx = _dbFactory.CreateDbContext())
        {
            await new TaskRepository(ctx).SetRoadblockCountAsync(task.Id, result.Blocks.Count, CancellationToken.None);
        }
        var reviewResult = ComposeReviewResult(result.ResultMarkdown, result.Blocks);
        bool isStandalone = task.ParentTaskId is null && task.PlanningPhase == PlanningPhase.None;

        List<TaskEntity> pendingChildren = new();
        if (isStandalone)
        {
            using var ctx = _dbFactory.CreateDbContext();
            var children = await new TaskRepository(ctx).GetChildrenAsync(task.Id, CancellationToken.None);
            pendingChildren = children
                .Where(c => c.Status is TaskStatus.Idle or TaskStatus.Queued)
                .ToList();
        }

        if (isStandalone && pendingChildren.Count > 0)
        {
            await _state.SubmitForChildrenAsync(task.Id, finishedAt, reviewResult, CancellationToken.None);
            foreach (var child in pendingChildren)
                await _state.EnqueueAsync(child.Id, CancellationToken.None);
            await _broadcaster.WorkerLog(
                $"Finished \"{task.Title}\" (waiting on {pendingChildren.Count} improvement(s))",
                WorkerLogLevel.Success, DateTime.UtcNow);
            await _broadcaster.TaskFinished(slot, task.Id, "waiting_for_children", finishedAt);
        }
        else if (isStandalone)
        {
            await _state.SubmitForReviewAsync(task.Id, finishedAt, reviewResult, CancellationToken.None);
            await _broadcaster.WorkerLog($"Finished \"{task.Title}\" (waiting for review)", WorkerLogLevel.Success, DateTime.UtcNow);
            await _broadcaster.TaskFinished(slot, task.Id, "waiting_for_review", finishedAt);
        }
        else
        {
            await _state.CompleteAsync(task.Id, finishedAt, reviewResult, CancellationToken.None);
            await _broadcaster.WorkerLog($"Finished \"{task.Title}\" (done)", WorkerLogLevel.Success, DateTime.UtcNow);
            await _broadcaster.TaskFinished(slot, task.Id, "done", finishedAt);
        }
        _logger.LogInformation("Task {TaskId} completed (turns={Turns}, tokens_in={In}, tokens_out={Out})",
            task.Id, result.TurnCount, result.TokensIn, result.TokensOut);
    }

    private async Task MarkFailed(string taskId, string taskTitle, string slot, string? error, int turnCount = 0)
    {
        // Terminal write for a failed task: never cancel (the status must always
        // be persisted) and never throw (a logging failure must not mask the error).
        try
        {
            var finishedAt = DateTime.UtcNow;
            await _state.FailAsync(taskId, finishedAt, error, CancellationToken.None);
            await _broadcaster.WorkerLog($"Finished \"{taskTitle}\" (failed)", WorkerLogLevel.Error, DateTime.UtcNow);
            await _broadcaster.TaskFinished(slot, taskId, "failed", finishedAt);
            _logger.LogWarning("Task {TaskId} failed (turns={Turns}): {Error}", taskId, turnCount, error);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Failed to mark task {TaskId} as failed", taskId);
        }
    }

    private string BuildRunMcpConfigJson(string token)
    {
        var payload = new
        {
            mcpServers = new
            {
                claudedo_run = new
                {
                    type = "http",
                    url = $"http://127.0.0.1:{_cfg.SignalRPort}/mcp",
                    headers = new Dictionary<string, string>
                    {
                        ["Authorization"] = $"Bearer {token}",
                    },
                },
            },
        };
        return JsonSerializer.Serialize(payload, new JsonSerializerOptions { WriteIndented = true });
    }

    private async Task<ClaudeRunConfig> ResolveConfigAsync(
        TaskEntity task, ListConfigEntity? listConfig, string? resumeSessionId, CancellationToken ct)
    {
        AppSettingsEntity global;
        using (var ctx = _dbFactory.CreateDbContext())
        {
            var settingsRepo = new AppSettingsRepository(ctx);
            global = await settingsRepo.GetAsync(ct);
        }

        var systemFile = PromptFiles.ReadOrDefault(PromptKind.System);

        // Improvement children (filed via SuggestImprovement; CreatedBy == ParentTaskId) get a
        // narrow follow-up prompt so they stay tightly scoped instead of doing "too much".
        var isImprovementChild = task.ParentTaskId is not null && task.CreatedBy == task.ParentTaskId;
        var improvementPrompt = isImprovementChild ? PromptFiles.ReadOrDefault(PromptKind.ImprovementChild) : null;

        var instructions = MergeInstructions(
            systemFile, improvementPrompt, global.DefaultClaudeInstructions, listConfig?.SystemPrompt, task.SystemPrompt);

        return new ClaudeRunConfig(
            Model: task.Model ?? listConfig?.Model ?? global.DefaultModel,
            SystemPrompt: string.IsNullOrWhiteSpace(instructions) ? null : instructions,
            AgentPath: task.AgentPath ?? listConfig?.AgentPath,
            ResumeSessionId: resumeSessionId,
            MaxTurns: ResolveMaxTurns(task.MaxTurns, listConfig?.MaxTurns, global.DefaultMaxTurns),
            PermissionMode: global.DefaultPermissionMode);
    }

    internal static int? ResolveMaxTurns(int? taskTurns, int? listTurns, int globalDefault)
        => taskTurns ?? listTurns ?? globalDefault;

    public static string MergeInstructions(params string?[] parts)
    {
        var trimmed = parts
            .Where(p => !string.IsNullOrWhiteSpace(p))
            .Select(p => p!.Trim());
        return string.Join("\n\n", trimmed);
    }

    public static string BuildRetryPrompt(string? capturedError)
    {
        var basePrompt = PromptFiles.ReadOrDefault(PromptKind.Retry);
        var isReal = !string.IsNullOrWhiteSpace(capturedError)
            && !capturedError!.StartsWith(ClaudeProcess.NoResultPrefix, StringComparison.Ordinal);
        return isReal
            ? $"{basePrompt}\n\nCaptured error from the failed run:\n\n{capturedError!.Trim()}"
            : basePrompt;
    }

    public static string? ComposeReviewResult(string? result, IReadOnlyList<string> blocks)
    {
        if (blocks.Count == 0) return result;
        var section = "⚠ Roadblocks reported during the run:\n"
            + string.Join('\n', blocks.Select(b => $"- {b}"));
        return string.IsNullOrWhiteSpace(result) ? section : $"{result}\n\n{section}";
    }
}