using System;
using System.Collections.Generic;
using System.Collections.Immutable;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Threading;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Routing;
using Microsoft.Extensions.Primitives;
using StellaOps.Scheduler.ImpactIndex;
using StellaOps.Scheduler.Models;
using StellaOps.Scheduler.Storage.Postgres.Repositories;
using StellaOps.Scheduler.WebService.Auth;

namespace StellaOps.Scheduler.WebService.Runs;

internal static class RunEndpoints
{
    private const string ReadScope = "scheduler.runs.read";
    private const string WriteScope = "scheduler.runs.write";
    private const string PreviewScope = "scheduler.runs.preview";
    private const string ManageScope = "scheduler.runs.manage";
    private const int DefaultRunListLimit = 50;

    public static IEndpointRouteBuilder MapRunEndpoints(this IEndpointRouteBuilder routes)
    {
        var group = routes.MapGroup("/api/v1/scheduler/runs");

        group.MapGet("/", ListRunsAsync);
        group.MapGet("/queue/lag", GetQueueLagAsync);
        group.MapGet("/{runId}/deltas", GetRunDeltasAsync);
        group.MapGet("/{runId}/stream", StreamRunAsync);
        group.MapGet("/{runId}", GetRunAsync);
        group.MapPost("/", CreateRunAsync);
        group.MapPost("/{runId}/cancel", CancelRunAsync);
        group.MapPost("/{runId}/retry", RetryRunAsync);
        group.MapPost("/preview", PreviewImpactAsync);

        return routes;
    }

    private static IResult GetQueueLagAsync(
        HttpContext httpContext,
        [FromServices] ITenantContextAccessor tenantAccessor,
        [FromServices] IScopeAuthorizer scopeAuthorizer,
        [FromServices] IQueueLagSummaryProvider queueLagProvider)
    {
        try
        {
            scopeAuthorizer.EnsureScope(httpContext, ReadScope);
            tenantAccessor.GetTenant(httpContext);

            var summary = queueLagProvider.Capture();
            return Results.Ok(summary);
        }
        catch (Exception ex) when (ex is ArgumentException or ValidationException)
        {
            return Results.BadRequest(new { error = ex.Message });
        }
    }

    private static async Task<IResult> ListRunsAsync(
        HttpContext httpContext,
        [FromServices] ITenantContextAccessor tenantAccessor,
        [FromServices] IScopeAuthorizer scopeAuthorizer,
        [FromServices] IRunRepository repository,
        CancellationToken cancellationToken)
    {
        try
        {
            scopeAuthorizer.EnsureScope(httpContext, ReadScope);
            var tenant = tenantAccessor.GetTenant(httpContext);

            var scheduleId = httpContext.Request.Query.TryGetValue("scheduleId", out var scheduleValues)
                ? scheduleValues.ToString().Trim()
                : null;

            var states = ParseRunStates(httpContext.Request.Query.TryGetValue("state", out var stateValues) ? stateValues : StringValues.Empty);
            var createdAfter = SchedulerEndpointHelpers.TryParseDateTimeOffset(httpContext.Request.Query.TryGetValue("createdAfter", out var createdAfterValues) ? createdAfterValues.ToString() : null);
            var limit = SchedulerEndpointHelpers.TryParsePositiveInt(httpContext.Request.Query.TryGetValue("limit", out var limitValues) ? limitValues.ToString() : null);
            var cursor = SchedulerEndpointHelpers.TryParseRunCursor(httpContext.Request.Query.TryGetValue("cursor", out var cursorValues) ? cursorValues.ToString() : null);

            var sortAscending = httpContext.Request.Query.TryGetValue("sort", out var sortValues) &&
                                 sortValues.Any(value => string.Equals(value, "asc", StringComparison.OrdinalIgnoreCase));

            var appliedLimit = limit ?? DefaultRunListLimit;
            var options = new RunQueryOptions
            {
                ScheduleId = string.IsNullOrWhiteSpace(scheduleId) ? null : scheduleId,
                States = states,
                CreatedAfter = createdAfter,
                Cursor = cursor,
                Limit = appliedLimit,
                SortAscending = sortAscending,
            };

            var runs = await repository.ListAsync(tenant.TenantId, options, cancellationToken: cancellationToken).ConfigureAwait(false);

            string? nextCursor = null;
            if (runs.Count == appliedLimit && runs.Count > 0)
            {
                var last = runs[^1];
                nextCursor = SchedulerEndpointHelpers.CreateRunCursor(last);
            }

            return Results.Ok(new RunCollectionResponse(runs, nextCursor));
        }
        catch (Exception ex) when (ex is ArgumentException or ValidationException)
        {
            return Results.BadRequest(new { error = ex.Message });
        }
    }

    private static async Task<IResult> GetRunAsync(
        HttpContext httpContext,
        string runId,
        [FromServices] ITenantContextAccessor tenantAccessor,
        [FromServices] IScopeAuthorizer scopeAuthorizer,
        [FromServices] IRunRepository repository,
        CancellationToken cancellationToken)
    {
        try
        {
            scopeAuthorizer.EnsureScope(httpContext, ReadScope);
            var tenant = tenantAccessor.GetTenant(httpContext);

            var run = await repository.GetAsync(tenant.TenantId, runId, cancellationToken: cancellationToken).ConfigureAwait(false);
            if (run is null)
            {
                return Results.NotFound();
            }

            return Results.Ok(new RunResponse(run));
        }
        catch (Exception ex) when (ex is ArgumentException or ValidationException)
        {
            return Results.BadRequest(new { error = ex.Message });
        }
    }

    private static async Task<IResult> GetRunDeltasAsync(
        HttpContext httpContext,
        string runId,
        [FromServices] ITenantContextAccessor tenantAccessor,
        [FromServices] IScopeAuthorizer scopeAuthorizer,
        [FromServices] IRunRepository repository,
        CancellationToken cancellationToken)
    {
        try
        {
            scopeAuthorizer.EnsureScope(httpContext, ReadScope);
            var tenant = tenantAccessor.GetTenant(httpContext);

            var run = await repository.GetAsync(tenant.TenantId, runId, cancellationToken: cancellationToken).ConfigureAwait(false);
            if (run is null)
            {
                return Results.NotFound();
            }

            return Results.Ok(new RunDeltaCollectionResponse(run.Deltas));
        }
        catch (Exception ex) when (ex is ArgumentException or ValidationException)
        {
            return Results.BadRequest(new { error = ex.Message });
        }
    }

    private static async Task<IResult> CreateRunAsync(
        HttpContext httpContext,
        RunCreateRequest request,
        [FromServices] ITenantContextAccessor tenantAccessor,
        [FromServices] IScopeAuthorizer scopeAuthorizer,
        [FromServices] IScheduleRepository scheduleRepository,
        [FromServices] IRunRepository runRepository,
        [FromServices] IRunSummaryService runSummaryService,
        [FromServices] ISchedulerAuditService auditService,
        [FromServices] TimeProvider timeProvider,
        CancellationToken cancellationToken)
    {
        try
        {
            scopeAuthorizer.EnsureScope(httpContext, ManageScope);
            var tenant = tenantAccessor.GetTenant(httpContext);

            if (string.IsNullOrWhiteSpace(request.ScheduleId))
            {
                throw new ValidationException("scheduleId must be provided when creating a run.");
            }

            var scheduleId = request.ScheduleId!.Trim();
            if (scheduleId.Length == 0)
            {
                throw new ValidationException("scheduleId must contain a value.");
            }

            var schedule = await scheduleRepository.GetAsync(tenant.TenantId, scheduleId, cancellationToken: cancellationToken).ConfigureAwait(false);
            if (schedule is null)
            {
                return Results.NotFound();
            }

            if (request.Trigger != RunTrigger.Manual)
            {
                throw new ValidationException("Only manual runs can be created via this endpoint.");
            }

            var now = timeProvider.GetUtcNow();
            var runId = SchedulerEndpointHelpers.GenerateIdentifier("run");
            var reason = request.Reason ?? RunReason.Empty;

            var run = new Run(
                runId,
                tenant.TenantId,
                request.Trigger,
                RunState.Planning,
                RunStats.Empty,
                now,
                reason,
                schedule.Id);

            await runRepository.InsertAsync(run, cancellationToken: cancellationToken).ConfigureAwait(false);

            if (!string.IsNullOrWhiteSpace(run.ScheduleId))
            {
                await runSummaryService.ProjectAsync(run, cancellationToken).ConfigureAwait(false);
            }

            await auditService.WriteAsync(
                new SchedulerAuditEvent(
                    tenant.TenantId,
                    "scheduler.run",
                    "create",
                    SchedulerEndpointHelpers.ResolveAuditActor(httpContext),
                    RunId: run.Id,
                    ScheduleId: schedule.Id,
                    Metadata: BuildMetadata(
                        ("state", run.State.ToString().ToLowerInvariant()),
                        ("trigger", run.Trigger.ToString().ToLowerInvariant()),
                        ("correlationId", request.CorrelationId?.Trim()))),
                cancellationToken).ConfigureAwait(false);

            return Results.Created($"/api/v1/scheduler/runs/{run.Id}", new RunResponse(run));
        }
        catch (Exception ex) when (ex is ArgumentException or ValidationException)
        {
            return Results.BadRequest(new { error = ex.Message });
        }
    }

    private static async Task<IResult> CancelRunAsync(
        HttpContext httpContext,
        string runId,
        [FromServices] ITenantContextAccessor tenantAccessor,
        [FromServices] IScopeAuthorizer scopeAuthorizer,
        [FromServices] IRunRepository repository,
        [FromServices] IRunSummaryService runSummaryService,
        [FromServices] ISchedulerAuditService auditService,
        [FromServices] TimeProvider timeProvider,
        CancellationToken cancellationToken)
    {
        try
        {
            scopeAuthorizer.EnsureScope(httpContext, WriteScope);
            var tenant = tenantAccessor.GetTenant(httpContext);

            var run = await repository.GetAsync(tenant.TenantId, runId, cancellationToken: cancellationToken).ConfigureAwait(false);
            if (run is null)
            {
                return Results.NotFound();
            }

            if (RunStateMachine.IsTerminal(run.State))
            {
                return Results.Conflict(new { error = "Run is already in a terminal state." });
            }

            var now = timeProvider.GetUtcNow();
            var cancelled = RunStateMachine.EnsureTransition(run, RunState.Cancelled, now);
            var updated = await repository.UpdateAsync(cancelled, cancellationToken: cancellationToken).ConfigureAwait(false);
            if (!updated)
            {
                return Results.Conflict(new { error = "Run could not be updated because it changed concurrently." });
            }

            if (!string.IsNullOrWhiteSpace(cancelled.ScheduleId))
            {
                await runSummaryService.ProjectAsync(cancelled, cancellationToken).ConfigureAwait(false);
            }

            await auditService.WriteAsync(
                new SchedulerAuditEvent(
                    tenant.TenantId,
                    "scheduler.run",
                    "cancel",
                    SchedulerEndpointHelpers.ResolveAuditActor(httpContext),
                    RunId: cancelled.Id,
                    ScheduleId: cancelled.ScheduleId,
                    Metadata: BuildMetadata(("state", cancelled.State.ToString().ToLowerInvariant()))),
                cancellationToken).ConfigureAwait(false);

            return Results.Ok(new RunResponse(cancelled));
        }
        catch (InvalidOperationException ex)
        {
            return Results.BadRequest(new { error = ex.Message });
        }
        catch (Exception ex) when (ex is ArgumentException or ValidationException)
        {
            return Results.BadRequest(new { error = ex.Message });
        }
    }

    private static async Task<IResult> RetryRunAsync(
        HttpContext httpContext,
        string runId,
        [FromServices] ITenantContextAccessor tenantAccessor,
        [FromServices] IScopeAuthorizer scopeAuthorizer,
        [FromServices] IScheduleRepository scheduleRepository,
        [FromServices] IRunRepository runRepository,
        [FromServices] IRunSummaryService runSummaryService,
        [FromServices] ISchedulerAuditService auditService,
        [FromServices] TimeProvider timeProvider,
        CancellationToken cancellationToken)
    {
        try
        {
            scopeAuthorizer.EnsureScope(httpContext, ManageScope);
            var tenant = tenantAccessor.GetTenant(httpContext);

            var existing = await runRepository.GetAsync(tenant.TenantId, runId, cancellationToken: cancellationToken).ConfigureAwait(false);
            if (existing is null)
            {
                return Results.NotFound();
            }

            if (string.IsNullOrWhiteSpace(existing.ScheduleId))
            {
                return Results.BadRequest(new { error = "Run cannot be retried because it is not associated with a schedule." });
            }

            if (!RunStateMachine.IsTerminal(existing.State))
            {
                return Results.Conflict(new { error = "Run is not in a terminal state and cannot be retried." });
            }

            var schedule = await scheduleRepository.GetAsync(tenant.TenantId, existing.ScheduleId!, cancellationToken: cancellationToken).ConfigureAwait(false);
            if (schedule is null)
            {
                return Results.BadRequest(new { error = "Associated schedule no longer exists." });
            }

            var now = timeProvider.GetUtcNow();
            var newRunId = SchedulerEndpointHelpers.GenerateIdentifier("run");
            var baselineReason = existing.Reason ?? RunReason.Empty;
            var manualReason = string.IsNullOrWhiteSpace(baselineReason.ManualReason)
                ? $"retry-of:{existing.Id}"
                : $"{baselineReason.ManualReason};retry-of:{existing.Id}";

            var newReason = new RunReason(
                manualReason,
                baselineReason.ConselierExportId,
                baselineReason.ExcitorExportId,
                baselineReason.Cursor)
            {
                ImpactWindowFrom = baselineReason.ImpactWindowFrom,
                ImpactWindowTo = baselineReason.ImpactWindowTo
            };

            var retryRun = new Run(
                newRunId,
                tenant.TenantId,
                RunTrigger.Manual,
                RunState.Planning,
                RunStats.Empty,
                now,
                newReason,
                existing.ScheduleId,
                retryOf: existing.Id);

            await runRepository.InsertAsync(retryRun, cancellationToken: cancellationToken).ConfigureAwait(false);

            if (!string.IsNullOrWhiteSpace(retryRun.ScheduleId))
            {
                await runSummaryService.ProjectAsync(retryRun, cancellationToken).ConfigureAwait(false);
            }

            await auditService.WriteAsync(
                new SchedulerAuditEvent(
                    tenant.TenantId,
                    "scheduler.run",
                    "retry",
                    SchedulerEndpointHelpers.ResolveAuditActor(httpContext),
                    RunId: retryRun.Id,
                    ScheduleId: retryRun.ScheduleId,
                    Metadata: BuildMetadata(
                        ("state", retryRun.State.ToString().ToLowerInvariant()),
                        ("retryOf", existing.Id),
                        ("trigger", retryRun.Trigger.ToString().ToLowerInvariant()))),
                cancellationToken).ConfigureAwait(false);

            return Results.Created($"/api/v1/scheduler/runs/{retryRun.Id}", new RunResponse(retryRun));
        }
        catch (InvalidOperationException ex)
        {
            return Results.BadRequest(new { error = ex.Message });
        }
        catch (Exception ex) when (ex is ArgumentException or ValidationException)
        {
            return Results.BadRequest(new { error = ex.Message });
        }
    }

    private static async Task StreamRunAsync(
        HttpContext httpContext,
        string runId,
        [FromServices] ITenantContextAccessor tenantAccessor,
        [FromServices] IScopeAuthorizer scopeAuthorizer,
        [FromServices] IRunRepository runRepository,
        [FromServices] IRunStreamCoordinator runStreamCoordinator,
        CancellationToken cancellationToken)
    {
        try
        {
            scopeAuthorizer.EnsureScope(httpContext, ReadScope);
            var tenant = tenantAccessor.GetTenant(httpContext);

            var run = await runRepository.GetAsync(tenant.TenantId, runId, cancellationToken: cancellationToken).ConfigureAwait(false);
            if (run is null)
            {
                await Results.NotFound().ExecuteAsync(httpContext);
                return;
            }

            await runStreamCoordinator.StreamAsync(httpContext, tenant.TenantId, run, cancellationToken).ConfigureAwait(false);
        }
        catch (OperationCanceledException) when (cancellationToken.IsCancellationRequested)
        {
            // Client disconnected; nothing to do.
        }
        catch (Exception ex) when (ex is ArgumentException or ValidationException)
        {
            if (!httpContext.Response.HasStarted)
            {
                await Results.BadRequest(new { error = ex.Message }).ExecuteAsync(httpContext);
            }
        }
    }

    private static async Task<IResult> PreviewImpactAsync(
        HttpContext httpContext,
        ImpactPreviewRequest request,
        [FromServices] ITenantContextAccessor tenantAccessor,
        [FromServices] IScopeAuthorizer scopeAuthorizer,
        [FromServices] IScheduleRepository scheduleRepository,
        [FromServices] IImpactIndex impactIndex,
        CancellationToken cancellationToken)
    {
        try
        {
            scopeAuthorizer.EnsureScope(httpContext, PreviewScope);
            var tenant = tenantAccessor.GetTenant(httpContext);

            var selector = await ResolveSelectorAsync(request, tenant.TenantId, scheduleRepository, cancellationToken).ConfigureAwait(false);

            var normalizedProductKeys = NormalizeStringInputs(request.ProductKeys);
            var normalizedVulnerabilityIds = NormalizeStringInputs(request.VulnerabilityIds);

            ImpactSet impactSet;
            if (!normalizedProductKeys.IsDefaultOrEmpty)
            {
                impactSet = await impactIndex.ResolveByPurlsAsync(normalizedProductKeys, request.UsageOnly, selector, cancellationToken).ConfigureAwait(false);
            }
            else if (!normalizedVulnerabilityIds.IsDefaultOrEmpty)
            {
                impactSet = await impactIndex.ResolveByVulnerabilitiesAsync(normalizedVulnerabilityIds, request.UsageOnly, selector, cancellationToken).ConfigureAwait(false);
            }
            else
            {
                impactSet = await impactIndex.ResolveAllAsync(selector, request.UsageOnly, cancellationToken).ConfigureAwait(false);
            }

            var sampleSize = Math.Clamp(request.SampleSize, 1, 50);
            var sampleBuilder = ImmutableArray.CreateBuilder<ImpactPreviewSample>();
            foreach (var image in impactSet.Images.Take(sampleSize))
            {
                sampleBuilder.Add(new ImpactPreviewSample(
                    image.ImageDigest,
                    image.Registry,
                    image.Repository,
                    image.Namespaces.IsDefault ? ImmutableArray<string>.Empty : image.Namespaces,
                    image.Tags.IsDefault ? ImmutableArray<string>.Empty : image.Tags,
                    image.UsedByEntrypoint));
            }

            var response = new ImpactPreviewResponse(
                impactSet.Total,
                impactSet.UsageOnly,
                impactSet.GeneratedAt,
                impactSet.SnapshotId,
                sampleBuilder.ToImmutable());

            return Results.Ok(response);
        }
        catch (KeyNotFoundException)
        {
            return Results.NotFound();
        }
        catch (Exception ex) when (ex is ArgumentException or ValidationException)
        {
            return Results.BadRequest(new { error = ex.Message });
        }
    }

    private static ImmutableArray<RunState> ParseRunStates(StringValues values)
    {
        if (values.Count == 0)
        {
            return ImmutableArray<RunState>.Empty;
        }

        var builder = ImmutableArray.CreateBuilder<RunState>();
        foreach (var value in values)
        {
            if (string.IsNullOrWhiteSpace(value))
            {
                continue;
            }

            if (!Enum.TryParse<RunState>(value, ignoreCase: true, out var parsed))
            {
                throw new ValidationException($"State '{value}' is not a valid run state.");
            }

            builder.Add(parsed);
        }

        return builder.ToImmutable();
    }

    private static async Task<Selector> ResolveSelectorAsync(
        ImpactPreviewRequest request,
        string tenantId,
        IScheduleRepository scheduleRepository,
        CancellationToken cancellationToken)
    {
        Selector? selector = null;

        if (!string.IsNullOrWhiteSpace(request.ScheduleId))
        {
            var schedule = await scheduleRepository.GetAsync(tenantId, request.ScheduleId!, cancellationToken: cancellationToken).ConfigureAwait(false);
            if (schedule is null)
            {
                throw new KeyNotFoundException($"Schedule '{request.ScheduleId}' was not found for tenant '{tenantId}'.");
            }

            selector = schedule.Selection;
        }

        if (request.Selector is not null)
        {
            if (selector is not null && request.ScheduleId is not null)
            {
                throw new ValidationException("selector cannot be combined with scheduleId in the same request.");
            }

            selector = request.Selector;
        }

        if (selector is null)
        {
            throw new ValidationException("Either scheduleId or selector must be provided.");
        }

        return SchedulerEndpointHelpers.NormalizeSelector(selector, tenantId);
    }

    private static ImmutableArray<string> NormalizeStringInputs(ImmutableArray<string>? values)
    {
        if (values is null || values.Value.IsDefaultOrEmpty)
        {
            return ImmutableArray<string>.Empty;
        }

        var builder = ImmutableArray.CreateBuilder<string>();
        var seen = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
        foreach (var value in values.Value)
        {
            if (string.IsNullOrWhiteSpace(value))
            {
                continue;
            }

            var trimmed = value.Trim();
            if (seen.Add(trimmed))
            {
                builder.Add(trimmed);
            }
        }

        return builder.ToImmutable();
    }

    private static IReadOnlyDictionary<string, string> BuildMetadata(params (string Key, string? Value)[] pairs)
    {
        var metadata = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
        foreach (var (key, value) in pairs)
        {
            if (string.IsNullOrWhiteSpace(key) || string.IsNullOrWhiteSpace(value))
            {
                continue;
            }

            metadata[key] = value!;
        }

        return metadata;
    }
}