using System.ComponentModel;
using ModelContextProtocol.Server;

namespace ClaudeDo.Worker.External;

public sealed record BatchAddTaskInput(string Title, string? Description = null, string? Model = null);
public sealed record BatchSetMyDayInput(string TaskId, bool IsMyDay, int? SortOrder = null);

// task is populated when found and includeDescription=false (the default, lean reference);
// taskFull is populated when found and includeDescription=true (full task incl.
// Description/Result). Both are null when found=false.
public sealed record BatchGetTaskResult(string Id, bool Found, TaskRefDto? Task, TaskDto? TaskFull, string? Error);
public sealed record BatchAddTaskResult(int Index, string Title, bool Ok, TaskRefDto? Task, string? Error);
public sealed record BatchTaskResult(string TaskId, bool Ok, string? Error);
public sealed record BatchCancelResult(string TaskId, bool Ok, bool Cancelled, string? Error);
public sealed record BatchCleanupResult(string TaskId, bool Ok, bool Removed, bool BranchDeleted, string? Error);

/// <summary>
/// Batch variants of the single-entity tools on <see cref="ExternalMcpService"/>.
/// Every tool is best-effort: each item is attempted independently and reported in a
/// per-item result array (a failing item never aborts the rest). Operations run
/// sequentially — the underlying repositories share one scoped DbContext, which is not
/// thread-safe. Merge/review stay single-task (conflicts need the interactive resolver).
/// </summary>
[McpServerToolType]
public sealed class BatchMcpTools
{
    private const int MaxBatchSize = 100;

    private readonly ExternalMcpService _svc;

    public BatchMcpTools(ExternalMcpService svc) => _svc = svc;

    [McpServerTool, Description(
        "Fetch a snapshot of many tasks in one call (overview / polling a fan-out). " +
        "Returns one result per id: { id, found, task, taskFull, error }. " +
        "includeDescription=false (default): found tasks come back in `task` (lean reference, no " +
        "Description/Result). includeDescription=true: found tasks come back in `taskFull` (incl. " +
        "Description/Result) instead. A missing id is found=false (not an error; task and taskFull both null); " +
        "error is only set for an unexpected failure. Max 100 ids.")]
    public async Task<IReadOnlyList<BatchGetTaskResult>> BatchGetTasks(
        string[] taskIds, bool includeDescription = false, CancellationToken cancellationToken = default)
    {
        EnsureWithinCap(taskIds, nameof(taskIds));

        var results = new List<BatchGetTaskResult>(taskIds.Length);
        foreach (var id in taskIds)
        {
            try
            {
                if (includeDescription)
                {
                    var task = await _svc.GetTask(id, cancellationToken);
                    results.Add(new BatchGetTaskResult(id, true, null, task, null));
                }
                else
                {
                    var taskRef = await _svc.GetTaskRefAsync(id, cancellationToken);
                    results.Add(new BatchGetTaskResult(id, true, taskRef, null, null));
                }
            }
            catch (OperationCanceledException) { throw; }
            catch (InvalidOperationException)
            {
                results.Add(new BatchGetTaskResult(id, false, null, null, null));
            }
            catch (Exception ex)
            {
                results.Add(new BatchGetTaskResult(id, false, null, null, ex.Message));
            }
        }
        return results;
    }

    [McpServerTool, Description(
        "Create many tasks in one list at once. Each item: { title, description?, model? } " +
        "(model: haiku|sonnet|opus, blank = inherit list/global default). " +
        "queueImmediately enqueues every created task. " +
        "Returns one result per item: { index, title, ok, task, error }; task is a lean reference " +
        "(id, listId, title, status, sortOrder, isMyDay), not the description you just sent. Max 100 items.")]
    public async Task<IReadOnlyList<BatchAddTaskResult>> BatchAddTasks(
        string listId,
        BatchAddTaskInput[] tasks,
        string? createdBy = null,
        bool queueImmediately = false,
        CancellationToken cancellationToken = default)
    {
        EnsureWithinCap(tasks, nameof(tasks));

        var results = new List<BatchAddTaskResult>(tasks.Length);
        for (var i = 0; i < tasks.Length; i++)
        {
            var item = tasks[i];
            try
            {
                var created = await _svc.AddTask(
                    listId, item.Title, item.Description, createdBy,
                    queueImmediately, item.Model, cancellationToken);
                results.Add(new BatchAddTaskResult(i, item.Title, true, created, null));
            }
            catch (OperationCanceledException) { throw; }
            catch (Exception ex)
            {
                results.Add(new BatchAddTaskResult(i, item.Title, false, null, ex.Message));
            }
        }
        return results;
    }

    [McpServerTool, Description(
        "Set the status of many tasks at once. status is 'Idle', 'Queued', 'Cancelled' or 'Done' only — " +
        "same rule as update_task_status ('Done' is refused per-item for a task with an active worktree). " +
        "Returns one result per id: { taskId, ok, error }. Max 100 ids.")]
    public async Task<IReadOnlyList<BatchTaskResult>> BatchUpdateTaskStatus(
        string[] taskIds, string status, CancellationToken cancellationToken)
    {
        EnsureWithinCap(taskIds, nameof(taskIds));
        return await RunPerTaskAsync(taskIds,
            (id, ct) => _svc.UpdateTaskStatus(id, status, ct), cancellationToken);
    }

    [McpServerTool, Description(
        "Cancel many running tasks at once. Returns one result per id: " +
        "{ taskId, ok, cancelled, error }. cancelled=false means the task was not running. " +
        "Max 100 ids.")]
    public async Task<IReadOnlyList<BatchCancelResult>> BatchCancelTasks(
        string[] taskIds, CancellationToken cancellationToken)
    {
        EnsureWithinCap(taskIds, nameof(taskIds));

        var results = new List<BatchCancelResult>(taskIds.Length);
        foreach (var id in taskIds)
        {
            try
            {
                var r = await _svc.CancelTask(id, cancellationToken);
                results.Add(new BatchCancelResult(id, true, r.Cancelled, null));
            }
            catch (OperationCanceledException) { throw; }
            catch (Exception ex)
            {
                results.Add(new BatchCancelResult(id, false, false, ex.Message));
            }
        }
        return results;
    }

    [McpServerTool, Description(
        "Delete many tasks at once. A Running task is refused (cancel it first) and reported " +
        "as ok=false with its error. Returns one result per id: { taskId, ok, error }. Max 100 ids.")]
    public async Task<IReadOnlyList<BatchTaskResult>> BatchDeleteTasks(
        string[] taskIds, CancellationToken cancellationToken)
    {
        EnsureWithinCap(taskIds, nameof(taskIds));
        return await RunPerTaskAsync(taskIds,
            (id, ct) => _svc.DeleteTask(id, ct), cancellationToken);
    }

    [McpServerTool, Description(
        "Daily prep: set/clear MyDay for many tasks at once. Each item: { taskId, isMyDay, sortOrder? }. " +
        "Still cap-guarded — items that would exceed DailyPrepMaxTasks open MyDay tasks fail individually " +
        "(ok=false) without blocking the rest. Returns one result per item: { taskId, ok, error }. Max 100 items.")]
    public async Task<IReadOnlyList<BatchTaskResult>> BatchSetMyDay(
        BatchSetMyDayInput[] items, CancellationToken cancellationToken)
    {
        EnsureWithinCap(items, nameof(items));

        var results = new List<BatchTaskResult>(items.Length);
        foreach (var item in items)
        {
            try
            {
                await _svc.SetMyDay(item.TaskId, item.IsMyDay, item.SortOrder, cancellationToken);
                results.Add(new BatchTaskResult(item.TaskId, true, null));
            }
            catch (OperationCanceledException) { throw; }
            catch (Exception ex)
            {
                results.Add(new BatchTaskResult(item.TaskId, false, ex.Message));
            }
        }
        return results;
    }

    [McpServerTool, Description(
        "Remove the worktrees of many tasks at once (directory + git branch). " +
        "force=false refuses a dirty or Running worktree (reported ok=false); force=true removes " +
        "even a dirty worktree (uncommitted changes lost), still refusing Running tasks. " +
        "Returns one result per id: { taskId, ok, removed, branchDeleted, error }. Max 100 ids.")]
    public async Task<IReadOnlyList<BatchCleanupResult>> BatchCleanupTaskWorktrees(
        string[] taskIds, bool force = false, CancellationToken cancellationToken = default)
    {
        EnsureWithinCap(taskIds, nameof(taskIds));

        var results = new List<BatchCleanupResult>(taskIds.Length);
        foreach (var id in taskIds)
        {
            try
            {
                var r = await _svc.CleanupTaskWorktree(id, force, cancellationToken);
                results.Add(new BatchCleanupResult(id, true, r.Removed, r.BranchDeleted, null));
            }
            catch (OperationCanceledException) { throw; }
            catch (Exception ex)
            {
                results.Add(new BatchCleanupResult(id, false, false, false, ex.Message));
            }
        }
        return results;
    }

    private static async Task<IReadOnlyList<BatchTaskResult>> RunPerTaskAsync(
        string[] taskIds, Func<string, CancellationToken, Task> op, CancellationToken cancellationToken)
    {
        var results = new List<BatchTaskResult>(taskIds.Length);
        foreach (var id in taskIds)
        {
            try
            {
                await op(id, cancellationToken);
                results.Add(new BatchTaskResult(id, true, null));
            }
            catch (OperationCanceledException) { throw; }
            catch (Exception ex)
            {
                results.Add(new BatchTaskResult(id, false, ex.Message));
            }
        }
        return results;
    }

    private static void EnsureWithinCap<T>(IReadOnlyCollection<T>? items, string name)
    {
        if (items is null || items.Count == 0)
            throw new InvalidOperationException($"{name} is required and must contain at least one item.");
        if (items.Count > MaxBatchSize)
            throw new InvalidOperationException(
                $"Batch too large: {items.Count} items (max {MaxBatchSize}). Split into smaller batches.");
    }
}