using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
using NovelSoftware.Application;
using NovelSoftware.Domain.Entities;

namespace NovelSoftware.Infrastructure.Persistence;

/// <summary>
/// Stores a <see cref="DateTimeOffset"/> as UTC ticks. SQLite has no native type for it
/// and refuses to ORDER BY the default text form, which every "most recently updated
/// first" listing depends on. The domain only ever writes UtcNow, so normalising to UTC
/// loses nothing.
/// </summary>
internal sealed class UtcTicksConverter()
    : ValueConverter<DateTimeOffset, long>(
        value => value.UtcTicks,
        ticks => new DateTimeOffset(ticks, TimeSpan.Zero));

public class NovelDbContext(DbContextOptions<NovelDbContext> options)
    : DbContext(options), INovelDbContext
{
    public DbSet<Project> Projects => Set<Project>();
    public DbSet<Character> Characters => Set<Character>();
    public DbSet<CharacterRelationship> CharacterRelationships => Set<CharacterRelationship>();
    public DbSet<Beat> Beats => Set<Beat>();
    public DbSet<Tag> Tags => Set<Tag>();
    public DbSet<Chapter> Chapters => Set<Chapter>();
    public DbSet<Scene> Scenes => Set<Scene>();
    public DbSet<AgentConversation> Conversations => Set<AgentConversation>();
    public DbSet<AgentMessage> AgentMessages => Set<AgentMessage>();

    Task<int> INovelDbContext.SaveChangesAsync(CancellationToken cancellationToken) =>
        base.SaveChangesAsync(cancellationToken);

    protected override void ConfigureConventions(ModelConfigurationBuilder builder) =>
        builder.Properties<DateTimeOffset>().HaveConversion<UtcTicksConverter>();

    protected override void OnModelCreating(ModelBuilder builder)
    {
        builder.Entity<Project>(entity =>
        {
            entity.Property(p => p.Title).IsRequired().HasMaxLength(300);
            entity.HasMany(p => p.Characters).WithOne(c => c.Project!)
                .HasForeignKey(c => c.ProjectId).OnDelete(DeleteBehavior.Cascade);
            entity.HasMany(p => p.Chapters).WithOne(c => c.Project!)
                .HasForeignKey(c => c.ProjectId).OnDelete(DeleteBehavior.Cascade);
            entity.HasMany(p => p.Tags).WithOne(t => t.Project!)
                .HasForeignKey(t => t.ProjectId).OnDelete(DeleteBehavior.Cascade);
            entity.HasMany(p => p.Conversations).WithOne(c => c.Project!)
                .HasForeignKey(c => c.ProjectId).OnDelete(DeleteBehavior.Cascade);
        });

        builder.Entity<Character>(entity =>
        {
            entity.Property(c => c.Name).IsRequired().HasMaxLength(200);
            entity.Property(c => c.Role).HasConversion<string>().HasMaxLength(32);
            entity.HasIndex(c => c.ProjectId);

            entity.HasMany(c => c.Relationships).WithOne(r => r.Character!)
                .HasForeignKey(r => r.CharacterId).OnDelete(DeleteBehavior.Cascade);
        });

        builder.Entity<CharacterRelationship>(entity =>
        {
            entity.Property(r => r.RelationshipType).IsRequired().HasMaxLength(120);

            // Restrict on the inverse side: deleting a character should not silently take
            // the other character's relationship rows with it via a second cascade path,
            // which SQLite rejects as a multiple-cascade cycle.
            entity.HasOne(r => r.RelatedCharacter).WithMany()
                .HasForeignKey(r => r.RelatedCharacterId).OnDelete(DeleteBehavior.Restrict);
        });

        builder.Entity<Beat>(entity =>
        {
            entity.Property(b => b.Title).IsRequired().HasMaxLength(200);
            entity.HasIndex(b => new { b.ChapterId, b.SortOrder });

            entity.HasOne(b => b.Chapter).WithMany(c => c.Beats)
                .HasForeignKey(b => b.ChapterId).OnDelete(DeleteBehavior.Cascade);

            // A beat outlives the scene it was grouped under: deleting a scene is a
            // decision about prose, not about the plan.
            entity.HasOne(b => b.Scene).WithMany()
                .HasForeignKey(b => b.SceneId).OnDelete(DeleteBehavior.SetNull);

            entity.HasOne(b => b.Character).WithMany()
                .HasForeignKey(b => b.CharacterId).OnDelete(DeleteBehavior.SetNull);
        });

        builder.Entity<Tag>(entity =>
        {
            entity.Property(t => t.Name).IsRequired().HasMaxLength(64);
            entity.Property(t => t.Color).HasMaxLength(16);

            // One canonical tag per name per project, so "betrayal" always means the
            // same tag no matter where it was typed.
            entity.HasIndex(t => new { t.ProjectId, t.Name }).IsUnique();

            entity.HasMany(t => t.Characters).WithMany(c => c.Tags)
                .UsingEntity(join => join.ToTable("CharacterTags"));
            entity.HasMany(t => t.Chapters).WithMany(c => c.Tags)
                .UsingEntity(join => join.ToTable("ChapterTags"));
            entity.HasMany(t => t.Beats).WithMany(b => b.Tags)
                .UsingEntity(join => join.ToTable("BeatTags"));
        });

        builder.Entity<Chapter>(entity =>
        {
            entity.Property(c => c.Title).IsRequired().HasMaxLength(300);
            entity.Property(c => c.Status).HasConversion<string>().HasMaxLength(32);
            entity.HasIndex(c => new { c.ProjectId, c.Number });

            entity.HasOne(c => c.PovCharacter).WithMany()
                .HasForeignKey(c => c.PovCharacterId).OnDelete(DeleteBehavior.SetNull);

            entity.HasMany(c => c.Scenes).WithOne(s => s.Chapter!)
                .HasForeignKey(s => s.ChapterId).OnDelete(DeleteBehavior.Cascade);
        });

        builder.Entity<Scene>(entity =>
        {
            entity.Property(s => s.Title).IsRequired().HasMaxLength(300);
            entity.Property(s => s.Status).HasConversion<string>().HasMaxLength(32);
            entity.HasIndex(s => new { s.ChapterId, s.SortOrder });

            entity.HasOne(s => s.PovCharacter).WithMany()
                .HasForeignKey(s => s.PovCharacterId).OnDelete(DeleteBehavior.SetNull);
        });

        builder.Entity<AgentConversation>(entity =>
        {
            entity.Property(c => c.Title).IsRequired().HasMaxLength(200);
            entity.HasMany(c => c.Messages).WithOne(m => m.Conversation!)
                .HasForeignKey(m => m.ConversationId).OnDelete(DeleteBehavior.Cascade);
        });

        builder.Entity<AgentMessage>(entity =>
        {
            entity.Property(m => m.Role).HasConversion<string>().HasMaxLength(16);
            entity.HasIndex(m => new { m.ConversationId, m.Sequence }).IsUnique();
        });
    }
}