using Data.SeaHavenIndustries;
using Microsoft.Extensions.Options;
using SeaHaven.DataServices.Interfaces;
using SeaHaven.Services.Configuration;
using SeaHaven.Services.DTOs;
using SeaHaven.Services.Interfaces;
using System.Security.Claims;

namespace SeaHaven.Services.Implementation
{
    public class UpliftService : IUpliftService
    {
        private readonly IUpliftDataService _upliftData;
        private readonly IDispatchDataService _dispatchData;
        private readonly IVendorDocumentStoragePort _documentStorage;
        private readonly TimeProvider _timeProvider;
        private readonly ApprovalsOptions _approvalsOptions;

        public UpliftService(
            IUpliftDataService upliftData,
            IDispatchDataService dispatchData,
            IVendorDocumentStoragePort documentStorage,
            TimeProvider timeProvider,
            IOptions<ApprovalsOptions> approvalsOptions)
        {
            _upliftData = upliftData;
            _dispatchData = dispatchData;
            _documentStorage = documentStorage;
            _timeProvider = timeProvider;
            _approvalsOptions = approvalsOptions.Value;
        }

        public async Task<UpliftListResultDTO> ListAsync(ClaimsPrincipal user, string? status, int? tier, int page, int pageSize, CancellationToken cancellationToken)
        {
            var (total, items) = await _upliftData.GetPagedAsync(status, tier, page, pageSize, cancellationToken);

            var mapped = items.Select(r => new UpliftListItemDTO
            {
                Id = r.Id,
                DispatchId = r.DispatchId,
                DispatchNumber = r.DispatchNumber,
                PONumber = r.PONumber,
                WorkOrderId = r.WorkOrderId,
                VendorCompanyName = r.VendorCompanyName,
                CurrentNTE = r.CurrentNTE,
                RequestedNTE = r.RequestedNTE,
                Delta = r.RequestedNTE - (r.CurrentNTE ?? 0m),
                VendorReason = r.VendorReason,
                RequiredTier = r.RequiredTier,
                Status = UpliftStatus.ToCanonical(r.Status),
                RequestedAt = r.CreatedDate,
                DecidedAt = r.DecidedAt,
                DecisionNote = r.DecisionNote,
                CanDecide = UserCanApprove(user, r.RequiredTier),
                EvidenceDocumentId = r.EvidenceDocumentId,
                EvidenceFileName = r.EvidenceFileName,
                EvidenceContentType = r.EvidenceContentType,
                EvidenceSizeBytes = r.EvidenceSizeBytes,
                ExpiresAt = r.ExpiresAt,
                NotificationStatus = r.NotificationStatus,
                NotificationError = r.NotificationError
            }).ToList();

            return new UpliftListResultDTO
            {
                Total = total,
                Page = page,
                PageSize = pageSize,
                Items = mapped
            };
        }

        public async Task<IEnumerable<UpliftForDispatchDTO>> ListForDispatchAsync(ClaimsPrincipal user, int dispatchId, CancellationToken cancellationToken)
        {
            var rows = await _upliftData.GetForDispatchAsync(dispatchId, cancellationToken);

            return rows.Select(r => new UpliftForDispatchDTO
            {
                Id = r.Id,
                DispatchId = r.DispatchId,
                CurrentNTE = r.CurrentNTE,
                RequestedNTE = r.RequestedNTE,
                Delta = r.RequestedNTE - (r.CurrentNTE ?? 0m),
                VendorReason = r.VendorReason,
                Status = UpliftStatus.ToCanonical(r.Status),
                RequiredTier = r.RequiredTier,
                RequestedByVendorName = r.RequestedByVendorName,
                RequestedAt = r.CreatedDate,
                DecidedAt = r.DecidedAt,
                DecisionNote = r.DecisionNote,
                DecidedByName = string.Join(" ", new[] { r.DecidedByFirstName, r.DecidedByLastName }
                    .Where(s => !string.IsNullOrWhiteSpace(s))).Trim(),
                CanDecide = UserCanApprove(user, r.RequiredTier),
                EvidenceDocumentId = r.EvidenceDocumentId,
                EvidenceFileName = r.EvidenceFileName,
                EvidenceContentType = r.EvidenceContentType,
                EvidenceSizeBytes = r.EvidenceSizeBytes,
                EvidenceScanPassed = r.EvidenceScanPassed,
                ExpiresAt = r.ExpiresAt,
                NotificationStatus = r.NotificationStatus,
                NotificationError = r.NotificationError
            }).ToList();
        }

        public async Task<UpliftApproveResultDTO> ApproveAsync(ClaimsPrincipal user, int id, string? note, CancellationToken cancellationToken)
        {
            var req = await _upliftData.GetByIdAsync(id, cancellationToken);
            if (req == null) throw new KeyNotFoundException("Uplift request not found");
            if (UpliftStatus.IsTerminal(req.Status))
                throw new InvalidOperationException($"Cannot approve a '{UpliftStatus.ToCanonical(req.Status)}' request");
            if (!UpliftStatus.CanTransition(req.Status, UpliftStatus.Approved))
                throw new InvalidOperationException($"Cannot approve a '{UpliftStatus.ToCanonical(req.Status)}' request");
            if (!UserCanApprove(user, req.RequiredTier))
                throw new UpliftForbiddenException($"Approval requires a Tier {req.RequiredTier} role");

            var dispatch = await _dispatchData.GetByIdAsync(req.DispatchId);
            if (dispatch == null) throw new KeyNotFoundException("Dispatch not found");
            if (IsTerminalForUplift(dispatch.Status))
                throw new InvalidOperationException($"Cannot approve uplift on a '{dispatch.Status}' dispatch");

            var userId = user.FindFirst(ClaimTypes.NameIdentifier)?.Value;
            var now = _timeProvider.GetUtcNow().UtcDateTime;
            var oldNTE = dispatch.NTEAmount ?? 0m;

            dispatch.NTEAmount = req.RequestedNTE;
            dispatch.LastModificationTime = now;

            req.Status = UpliftStatus.Approved;
            req.DecidedAt = now;
            req.DecidedByUserId = userId;
            req.DecisionNote = string.IsNullOrWhiteSpace(note) ? null : note!.Trim();
            req.LastModificationTime = now;

            await _dispatchData.StageAuditLogAsync(new WorkOrderAuditLog
            {
                WorkOrderId = dispatch.WorkOrderId ?? 0,
                UserId = userId,
                FieldName = $"Dispatch {dispatch.DispatchNumber} NTE",
                OldValue = $"${oldNTE:F2}",
                NewValue = $"${req.RequestedNTE:F2}",
                Action = "uplift_approved",
                CreatedAt = now
            }, cancellationToken);

            // One EF unit-of-work commit for the dispatch RowVersion-protected NTE + request + audit.
            await _upliftData.SaveChangesAsync(cancellationToken);
            return new UpliftApproveResultDTO { Id = req.Id, Status = UpliftStatus.Approved, NTEAmount = dispatch.NTEAmount };
        }

        public async Task<UpliftDenyResultDTO> DenyAsync(ClaimsPrincipal user, int id, string? note, CancellationToken cancellationToken)
        {
            var result = await RejectInternalAsync(user, id, note, "deny", cancellationToken);
            return new UpliftDenyResultDTO { Id = result.Id, Status = result.Status };
        }

        public Task<UpliftDecisionResultDTO> RejectAsync(ClaimsPrincipal user, int id, string? note, CancellationToken cancellationToken)
            => RejectInternalAsync(user, id, note, "reject", cancellationToken);

        private async Task<UpliftDecisionResultDTO> RejectInternalAsync(ClaimsPrincipal user, int id, string? note, string actionSuffix, CancellationToken cancellationToken)
        {
            if (string.IsNullOrWhiteSpace(note))
                throw new InvalidOperationException("A note is required when rejecting");

            var req = await _upliftData.GetByIdAsync(id, cancellationToken);
            if (req == null) throw new KeyNotFoundException("Uplift request not found");
            if (!UpliftStatus.CanTransition(req.Status, UpliftStatus.Rejected))
                throw new InvalidOperationException($"Cannot reject a '{UpliftStatus.ToCanonical(req.Status)}' request");
            if (!UserCanApprove(user, req.RequiredTier))
                throw new UpliftForbiddenException($"Decision requires a Tier {req.RequiredTier} role");

            var dispatch = await _dispatchData.GetByIdAsync(req.DispatchId);

            var userId = user.FindFirst(ClaimTypes.NameIdentifier)?.Value;
            var now = _timeProvider.GetUtcNow().UtcDateTime;

            // Capture the pre-transition canonical status before mutating req.Status,
            // otherwise the audit OldValue would record the already-applied Rejected value.
            var previous = UpliftStatus.ToCanonical(req.Status);
            req.Status = UpliftStatus.Rejected;
            req.DecidedAt = now;
            req.DecidedByUserId = userId;
            req.DecisionNote = note!.Trim();
            req.LastModificationTime = now;

            await _dispatchData.StageAuditLogAsync(new WorkOrderAuditLog
            {
                WorkOrderId = dispatch?.WorkOrderId ?? 0,
                UserId = userId,
                FieldName = $"Dispatch {dispatch?.DispatchNumber} Uplift",
                OldValue = previous,
                NewValue = UpliftStatus.Rejected,
                Action = $"uplift_{actionSuffix}",
                CreatedAt = now
            }, cancellationToken);

            await _upliftData.SaveChangesAsync(cancellationToken);
            return new UpliftDecisionResultDTO { Id = req.Id, Status = UpliftStatus.Rejected };
        }

        public async Task<UpliftDecisionResultDTO> RequestChangesAsync(ClaimsPrincipal user, int id, string note, CancellationToken cancellationToken)
        {
            if (string.IsNullOrWhiteSpace(note))
                throw new InvalidOperationException("A note is required when requesting changes");

            var req = await _upliftData.GetByIdAsync(id, cancellationToken);
            if (req == null) throw new KeyNotFoundException("Uplift request not found");
            if (!UpliftStatus.CanTransition(req.Status, UpliftStatus.ChangesRequested))
                throw new InvalidOperationException($"Cannot request changes on a '{UpliftStatus.ToCanonical(req.Status)}' request");
            if (!UserCanApprove(user, req.RequiredTier))
                throw new UpliftForbiddenException($"Requesting changes requires a Tier {req.RequiredTier} role");

            var dispatch = await _dispatchData.GetByIdAsync(req.DispatchId);
            var userId = user.FindFirst(ClaimTypes.NameIdentifier)?.Value;
            var now = _timeProvider.GetUtcNow().UtcDateTime;

            var previous = UpliftStatus.ToCanonical(req.Status);
            req.Status = UpliftStatus.ChangesRequested;
            req.DecidedAt = now;
            req.DecidedByUserId = userId;
            req.DecisionNote = note.Trim();
            req.LastModificationTime = now;

            await _dispatchData.StageAuditLogAsync(new WorkOrderAuditLog
            {
                WorkOrderId = dispatch?.WorkOrderId ?? 0,
                UserId = userId,
                FieldName = $"Dispatch {dispatch?.DispatchNumber} Uplift",
                OldValue = previous,
                NewValue = UpliftStatus.ChangesRequested,
                Action = "uplift_changes_requested",
                CreatedAt = now
            }, cancellationToken);

            await _upliftData.SaveChangesAsync(cancellationToken);
            return new UpliftDecisionResultDTO { Id = req.Id, Status = UpliftStatus.ChangesRequested };
        }

        public bool CanApprove(ClaimsPrincipal user, int tier) => UserCanApprove(user, tier);

        // SH-101: authorized internal download of a Passed UpliftEvidence file. The data
        // service resolves the document by the request's own linkage (no client-supplied
        // document id or vendor/public path). Only UpliftEvidence documents are exposed;
        // completion documents resolve to NotFound. A scan that has not Passed is Locked.
        public async Task<UpliftEvidenceDownloadResultDTO> GetEvidenceForDownloadAsync(ClaimsPrincipal user, int id, CancellationToken cancellationToken)
        {
            var evidence = await _upliftData.GetEvidenceForInternalDownloadAsync(id, cancellationToken);
            if (evidence == null
                || evidence.EvidenceDocumentId == null
                || !string.Equals(evidence.Purpose, VendorDocumentPurpose.UpliftEvidence, StringComparison.Ordinal))
            {
                return UpliftEvidenceDownloadResultDTO.NotFound();
            }

            if (!UserCanApprove(user, evidence.RequiredTier))
            {
                throw new UpliftForbiddenException($"Evidence access requires a Tier {evidence.RequiredTier} role");
            }

            if (!string.Equals(evidence.ScanStatus, "Passed", StringComparison.OrdinalIgnoreCase))
            {
                return UpliftEvidenceDownloadResultDTO.Locked();
            }

            var content = _documentStorage.OpenRead(evidence.VendorId, evidence.DispatchId, evidence.StoredFileName ?? string.Empty);
            return UpliftEvidenceDownloadResultDTO.Ok(content, evidence.ContentType ?? "application/octet-stream", evidence.OriginalFileName ?? "evidence");
        }

        private bool UserCanApprove(ClaimsPrincipal user, int requiredTier)
        {
            var roles = RolesForTier(requiredTier);
            foreach (var r in roles)
            {
                if (!string.IsNullOrWhiteSpace(r) && user.IsInRole(r)) return true;
            }
            return false;
        }

        private string[] RolesForTier(int requiredTier) => requiredTier switch
        {
            1 => _approvalsOptions.Tier1Roles,
            2 => _approvalsOptions.Tier2Roles,
            _ => Array.Empty<string>()
        };

        // Terminal dispatch guard for uplift decisions. "Refused" is the SH-98
        // dispatch-refusal workflow; a refused dispatch is terminal for uplift just
        // like Verified/Cancelled.
        private static bool IsTerminalForUplift(string? status) =>
            status is "Verified" or "Cancelled" or "Canceled" or "Refused";
    }
}