// <copyright file="FacetDriftVexWorkflow.cs" company="StellaOps">
// Copyright (c) StellaOps. Licensed under BUSL-1.1.
// </copyright>
// Sprint: SPRINT_20260105_002_003_FACET (QTA-019)

using System.Collections.Immutable;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Logging.Abstractions;

namespace StellaOps.Facet;

/// <summary>
/// Result of a facet drift VEX workflow execution.
/// </summary>
public sealed record FacetDriftVexWorkflowResult
{
    /// <summary>
    /// Emission result from the emitter.
    /// </summary>
    public required FacetDriftVexEmissionResult EmissionResult { get; init; }

    /// <summary>
    /// Number of drafts that were newly created.
    /// </summary>
    public int NewDraftsCreated { get; init; }

    /// <summary>
    /// Number of drafts that already existed (skipped).
    /// </summary>
    public int ExistingDraftsSkipped { get; init; }

    /// <summary>
    /// IDs of newly created drafts.
    /// </summary>
    public ImmutableArray<string> CreatedDraftIds { get; init; } = [];

    /// <summary>
    /// Any errors that occurred during storage.
    /// </summary>
    public ImmutableArray<string> Errors { get; init; } = [];

    /// <summary>
    /// Whether all operations completed successfully.
    /// </summary>
    public bool Success => Errors.Length == 0;
}

/// <summary>
/// Orchestrates the facet drift VEX workflow: emit drafts + store.
/// This integrates with the Excititor VEX workflow by providing
/// drafts that can be picked up for human review.
/// </summary>
public sealed class FacetDriftVexWorkflow
{
    private readonly FacetDriftVexEmitter _emitter;
    private readonly IFacetDriftVexDraftStore _draftStore;
    private readonly ILogger<FacetDriftVexWorkflow> _logger;
    private readonly TimeProvider _timeProvider;

    /// <summary>
    /// Initializes a new instance of the <see cref="FacetDriftVexWorkflow"/> class.
    /// </summary>
    public FacetDriftVexWorkflow(
        FacetDriftVexEmitter emitter,
        IFacetDriftVexDraftStore draftStore,
        ILogger<FacetDriftVexWorkflow>? logger = null,
        TimeProvider? timeProvider = null)
    {
        _emitter = emitter ?? throw new ArgumentNullException(nameof(emitter));
        _draftStore = draftStore ?? throw new ArgumentNullException(nameof(draftStore));
        _logger = logger ?? NullLogger<FacetDriftVexWorkflow>.Instance;
        _timeProvider = timeProvider ?? TimeProvider.System;
    }

    /// <summary>
    /// Executes the full workflow: emit drafts from drift report and store them.
    /// </summary>
    /// <param name="driftReport">The drift report to process.</param>
    /// <param name="skipExisting">If true, skip creating drafts that already exist.</param>
    /// <param name="ct">Cancellation token.</param>
    /// <returns>Workflow result with draft IDs and status.</returns>
    public async Task<FacetDriftVexWorkflowResult> ExecuteAsync(
        FacetDriftReport driftReport,
        bool skipExisting = true,
        CancellationToken ct = default)
    {
        ArgumentNullException.ThrowIfNull(driftReport);

        // Emit drafts from drift report
        var context = new FacetDriftVexEmissionContext(driftReport);
        var emissionResult = _emitter.EmitDrafts(context);

        if (emissionResult.DraftsEmitted == 0)
        {
            _logger.LogDebug("No drafts to emit for image {ImageDigest}", driftReport.ImageDigest);
            return new FacetDriftVexWorkflowResult
            {
                EmissionResult = emissionResult,
                NewDraftsCreated = 0,
                ExistingDraftsSkipped = 0
            };
        }

        // Store drafts
        var createdIds = new List<string>();
        var skippedCount = 0;
        var errors = new List<string>();

        foreach (var draft in emissionResult.Drafts)
        {
            ct.ThrowIfCancellationRequested();

            try
            {
                if (skipExisting)
                {
                    var exists = await _draftStore.ExistsAsync(
                        draft.ImageDigest,
                        draft.FacetId,
                        ct).ConfigureAwait(false);

                    if (exists)
                    {
                        _logger.LogDebug(
                            "Skipping existing draft for {ImageDigest}/{FacetId}",
                            draft.ImageDigest,
                            draft.FacetId);
                        skippedCount++;
                        continue;
                    }
                }

                await _draftStore.SaveAsync(draft, ct).ConfigureAwait(false);
                createdIds.Add(draft.DraftId);

                _logger.LogInformation(
                    "Created VEX draft {DraftId} for {ImageDigest}/{FacetId} with churn {ChurnPercent:F1}%",
                    draft.DraftId,
                    draft.ImageDigest,
                    draft.FacetId,
                    draft.DriftSummary.ChurnPercent);
            }
            catch (Exception ex) when (ex is not OperationCanceledException)
            {
                _logger.LogError(
                    ex,
                    "Failed to store draft for {ImageDigest}/{FacetId}",
                    draft.ImageDigest,
                    draft.FacetId);
                errors.Add($"Failed to store draft for {draft.FacetId}: {ex.Message}");
            }
        }

        return new FacetDriftVexWorkflowResult
        {
            EmissionResult = emissionResult,
            NewDraftsCreated = createdIds.Count,
            ExistingDraftsSkipped = skippedCount,
            CreatedDraftIds = [.. createdIds],
            Errors = [.. errors]
        };
    }

    /// <summary>
    /// Approves a draft and converts it to a VEX statement.
    /// </summary>
    /// <param name="draftId">ID of the draft to approve.</param>
    /// <param name="reviewedBy">Who approved the draft.</param>
    /// <param name="notes">Optional review notes.</param>
    /// <param name="ct">Cancellation token.</param>
    /// <returns>True if approval succeeded.</returns>
    public async Task<bool> ApproveAsync(
        string draftId,
        string reviewedBy,
        string? notes = null,
        CancellationToken ct = default)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(draftId);
        ArgumentException.ThrowIfNullOrWhiteSpace(reviewedBy);

        try
        {
            await _draftStore.UpdateReviewStatusAsync(
                draftId,
                FacetDriftVexReviewStatus.Approved,
                reviewedBy,
                notes,
                ct).ConfigureAwait(false);

            _logger.LogInformation(
                "Draft {DraftId} approved by {ReviewedBy}",
                draftId,
                reviewedBy);

            return true;
        }
        catch (KeyNotFoundException)
        {
            _logger.LogWarning("Draft {DraftId} not found for approval", draftId);
            return false;
        }
    }

    /// <summary>
    /// Rejects a draft.
    /// </summary>
    /// <param name="draftId">ID of the draft to reject.</param>
    /// <param name="reviewedBy">Who rejected the draft.</param>
    /// <param name="reason">Reason for rejection.</param>
    /// <param name="ct">Cancellation token.</param>
    /// <returns>True if rejection succeeded.</returns>
    public async Task<bool> RejectAsync(
        string draftId,
        string reviewedBy,
        string reason,
        CancellationToken ct = default)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(draftId);
        ArgumentException.ThrowIfNullOrWhiteSpace(reviewedBy);
        ArgumentException.ThrowIfNullOrWhiteSpace(reason);

        try
        {
            await _draftStore.UpdateReviewStatusAsync(
                draftId,
                FacetDriftVexReviewStatus.Rejected,
                reviewedBy,
                reason,
                ct).ConfigureAwait(false);

            _logger.LogInformation(
                "Draft {DraftId} rejected by {ReviewedBy}: {Reason}",
                draftId,
                reviewedBy,
                reason);

            return true;
        }
        catch (KeyNotFoundException)
        {
            _logger.LogWarning("Draft {DraftId} not found for rejection", draftId);
            return false;
        }
    }

    /// <summary>
    /// Gets drafts pending review.
    /// </summary>
    public Task<ImmutableArray<FacetDriftVexDraft>> GetPendingDraftsAsync(
        string? imageDigest = null,
        CancellationToken ct = default)
    {
        var query = new FacetDriftVexDraftQuery
        {
            ImageDigest = imageDigest,
            ReviewStatus = FacetDriftVexReviewStatus.Pending
        };

        return _draftStore.QueryAsync(query, ct);
    }

    /// <summary>
    /// Gets drafts that have exceeded their review deadline.
    /// </summary>
    public Task<ImmutableArray<FacetDriftVexDraft>> GetOverdueDraftsAsync(CancellationToken ct = default)
    {
        return _draftStore.GetOverdueAsync(_timeProvider.GetUtcNow(), ct);
    }
}