using HrynCo.NotificationService.DAL.Abstract.Repositories;
using HrynCo.NotificationService.DAL.Abstract.Templates;
using HrynCo.NotificationService.DAL.EF.Entities;
using Microsoft.EntityFrameworkCore;

namespace HrynCo.NotificationService.DAL.EF.Repositories;

internal sealed class PushTemplateDefinitionRepository(NotificationDbContext db, TemplateMutationRunner mutations)
    : IPushTemplateDefinitionRepository
{
    private IQueryable<PushTemplateDefinitionEntity> Definitions => db.PushTemplateDefinitions
        .Include(d => d.Languages).ThenInclude(l => l.ServiceLanguage);

    public async Task<IReadOnlyList<PushTemplateDefinition>> GetDefinitionsAsync(Guid serviceId, CancellationToken ct = default) =>
        (await Definitions.AsNoTracking().Where(d => d.ServiceId == serviceId).OrderBy(d => d.Key).ToListAsync(ct)).Select(Map).ToList();

    public async Task<PushTemplateDefinition?> GetAsync(Guid serviceId, string key, CancellationToken ct = default)
    {
        var entity = await Definitions.AsNoTracking().SingleOrDefaultAsync(d => d.ServiceId == serviceId && d.Key == key, ct);
        return entity is null ? null : Map(entity);
    }

    public Task SaveAsync(PushTemplateDefinition definition, bool isNew, CancellationToken ct = default) => mutations.ExecuteAsync(async () =>
    {
        PushTemplateValidation.Validate(definition);
        var service = await db.Services.Include(s => s.Languages).SingleOrDefaultAsync(s => s.Id == definition.ServiceId, ct)
            ?? throw new EmailTemplateWriteException("Service no longer exists. Reload services.");
        if (definition.Languages.Any(l => !service.Languages.Any(s => s.Code == l.LanguageCode)))
            throw new EmailTemplateWriteException("Every language must exactly match this service's catalog.", false);
        var entity = await LoadForSaveAsync(definition, service, isNew, ct);
        entity.Variables = definition.Variables.Select(v => new PushTemplateVariableData { Name = v.Name, Required = v.Required }).ToList();
        SynchronizeLanguages(entity, service, definition.Languages);
        entity.Revision = Guid.NewGuid();
        entity.Updated = DateTimeOffset.UtcNow;
        definition.Id = entity.Id;
        definition.Revision = entity.Revision;
    }, ct);

    private async Task<PushTemplateDefinitionEntity> LoadForSaveAsync(PushTemplateDefinition model, ServiceEntity service, bool isNew, CancellationToken ct)
    {
        var entity = await Definitions.SingleOrDefaultAsync(d => d.ServiceId == service.Id && d.Key == model.Key, ct);
        if (!isNew)
        {
            if (entity is null || entity.Id != model.Id || entity.Revision != model.Revision)
                throw new EmailTemplateWriteException("This push template changed after you opened it. Reload before saving; your entered values are retained.");
            return entity;
        }
        if (entity is not null)
            throw new EmailTemplateWriteException("A push template with this key already exists.");
        var template = await db.TemplateCatalog.SingleOrDefaultAsync(t => t.ServiceId == service.Id && t.Key == model.Key, ct)
            ?? new TemplateEntity { Service = service, ServiceId = service.Id, Key = model.Key, Created = DateTimeOffset.UtcNow };
        entity = new PushTemplateDefinitionEntity { Template = template, ServiceId = service.Id, Key = model.Key, Created = DateTimeOffset.UtcNow };
        db.PushTemplateDefinitions.Add(entity);
        return entity;
    }

    private void SynchronizeLanguages(PushTemplateDefinitionEntity definition, ServiceEntity service, IReadOnlyList<PushTemplateTranslation> translations)
    {
        var codes = translations.Select(l => l.LanguageCode).ToHashSet(StringComparer.Ordinal);
        db.PushTemplates.RemoveRange(definition.Languages.Where(l => !codes.Contains(l.ServiceLanguage.Code)));
        foreach (var translation in translations)
        {
            var entity = definition.Languages.SingleOrDefault(l => l.ServiceLanguage.Code == translation.LanguageCode);
            if (entity is null)
            {
                entity = new PushTemplateEntity
                {
                    Definition = definition, ServiceId = service.Id,
                    ServiceLanguage = service.Languages.Single(l => l.Code == translation.LanguageCode),
                    Title = translation.Title, Body = translation.Body, Created = DateTimeOffset.UtcNow
                };
                definition.Languages.Add(entity);
            }
            entity.Title = translation.Title;
            entity.Body = translation.Body;
            entity.ActionsJson = translation.ActionsJson;
            entity.Updated = DateTimeOffset.UtcNow;
        }
    }

    public async Task<bool> DeleteAsync(Guid serviceId, string key, Guid revision, CancellationToken ct = default)
    {
        var removed = false;
        await mutations.ExecuteAsync(async () =>
        {
            var entity = await Definitions.SingleOrDefaultAsync(d => d.ServiceId == serviceId && d.Key == key, ct);
            if (entity is null)
                return;
            if (revision == Guid.Empty || entity.Revision != revision)
                throw new EmailTemplateWriteException("The push template revision changed. Reload before deleting.");
            db.PushTemplateDefinitions.Remove(entity);
            if (!await db.TemplateDefinitions.AnyAsync(d => d.ServiceId == serviceId && d.Key == key, ct))
                db.TemplateCatalog.Remove(await db.TemplateCatalog.SingleAsync(t => t.ServiceId == serviceId && t.Key == key, ct));
            removed = true;
        }, ct);
        return removed;
    }

    private static PushTemplateDefinition Map(PushTemplateDefinitionEntity entity) => new()
    {
        Id = entity.Id, ServiceId = entity.ServiceId, Key = entity.Key, Revision = entity.Revision,
        Variables = entity.Variables.Select(v => new EmailTemplateVariable { Name = v.Name, Required = v.Required }).ToList(),
        Languages = entity.Languages.OrderBy(l => l.ServiceLanguage.Code).Select(l => new PushTemplateTranslation
        {
            LanguageCode = l.ServiceLanguage.Code, Title = l.Title, Body = l.Body, ActionsJson = l.ActionsJson
        }).ToList()
    };
}