using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.Json;
using FinlyticCore.Database;
using FinlyticCore.Dtos.TechnicalAnalysis;
using FinlyticCore.Dtos.Trading;
using FinlyticCore.Entities.Settings;
using FinlyticEngine.Database.Entities;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.ChangeTracking;
using Microsoft.EntityFrameworkCore.Design;
using Microsoft.EntityFrameworkCore.Storage.ValueConversion;

namespace FinlyticEngine.Database;

public class EngineDbContext : DbContext, ISettingsDbContext
{
    private static readonly JsonSerializerOptions JsonOptions = new()
    {
        PropertyNameCaseInsensitive = true,
        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
        WriteIndented = false
    };

    public EngineDbContext(DbContextOptions<EngineDbContext> options) : base(options)
    {
    }

    public DbSet<SettingEntity> DynamicSettings => Set<SettingEntity>();
    public DbSet<EngineTradeProposalEntity> TradeProposals => Set<EngineTradeProposalEntity>();
    public DbSet<EngineTradeEntity> Trades => Set<EngineTradeEntity>();
    public DbSet<EngineTradeFillEntity> TradeFills => Set<EngineTradeFillEntity>();
    public DbSet<EngineEvaluationSnapshotEntity> Snapshots => Set<EngineEvaluationSnapshotEntity>();
    public DbSet<EngineScanCycleEntity> ScanCycles => Set<EngineScanCycleEntity>();

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);

        // 1. Settings Table
        modelBuilder.Entity<SettingEntity>(entity =>
        {
            entity.HasKey(e => e.Id);
            entity.HasIndex(e => e.Key).IsUnique();
        });

        // 2. Converters for JSONB Columns
        var exitPlanConverter = new ValueConverter<ExitPlan, string>(
            v => JsonSerializer.Serialize(v, JsonOptions),
            v => JsonSerializer.Deserialize<ExitPlan>(v, JsonOptions) ?? new ExitPlan(ExitStrategyType.FixedSingleTarget, 0m, new List<TakeProfitStage>(), null, null, null, null)
        );

        var aiValidationConverter = new ValueConverter<AiValidationResultDto, string>(
            v => JsonSerializer.Serialize(v, JsonOptions),
            v => JsonSerializer.Deserialize<AiValidationResultDto>(v, JsonOptions) ?? new AiValidationResultDto(
                IsApproved: false,
                Confidence: null,
                Source: ValidationSource.RuleBased,
                ThesisSummary: "",
                InvalidationReason: "",
                KeyCatalysts: new List<string>(),
                IdentifiedRisks: new List<string>())
        );

        var derivativeSelectionConverter = new ValueConverter<DerivativeSelectionDto?, string>(
            v => v == null ? "{}" : JsonSerializer.Serialize(v, JsonOptions),
            v => string.IsNullOrWhiteSpace(v) || v == "{}" ? null : JsonSerializer.Deserialize<DerivativeSelectionDto>(v, JsonOptions)
        );

        var stringListConverter = new ValueConverter<List<string>, string>(
            v => JsonSerializer.Serialize(v, JsonOptions),
            v => JsonSerializer.Deserialize<List<string>>(v, JsonOptions) ?? new List<string>()
        );

        // EF Core cannot infer change-tracking equality for a mutable List<string> on its own; an explicit
        // comparer avoids a "detected changes every SaveChanges" model-validation warning for CandidateIsins.
        var stringListComparer = new ValueComparer<List<string>>(
            (a, b) => (a ?? new List<string>()).SequenceEqual(b ?? new List<string>()),
            v => v.Aggregate(0, (hash, s) => HashCode.Combine(hash, s.GetHashCode())),
            v => v.ToList()
        );

        // 3. Trade Proposals Table
        modelBuilder.Entity<EngineTradeProposalEntity>(entity =>
        {
            entity.HasKey(e => e.Id);
            entity.HasIndex(e => new { e.UnderlyingIsin, e.IsActive, e.ExpiresAtUtc });
            entity.HasIndex(e => e.CreatedAtUtc);
            entity.HasIndex(e => e.CompositeScore);

            entity.Property(e => e.ExitPlan)
                .HasColumnType("jsonb")
                .HasConversion(exitPlanConverter);

            entity.Property(e => e.AiValidation)
                .HasColumnType("jsonb")
                .HasConversion(aiValidationConverter);

            entity.Property(e => e.SelectedDerivative)
                .HasColumnType("jsonb")
                .HasConversion(derivativeSelectionConverter);
        });

        // 4. Active Trades Table
        modelBuilder.Entity<EngineTradeEntity>(entity =>
        {
            entity.HasKey(e => e.Id);
            entity.HasIndex(e => new { e.Status, e.UnderlyingIsin });
            entity.HasIndex(e => e.OpenedAtUtc);

            // Every trade read/mutation in TradeLifecycleService filters on (UserId, Status) together:
            // GetActiveTradesAsync always scopes to a single user's rows and then excludes terminal statuses,
            // and AddTradeFill/UpdateStopLoss/CloseTrade all load a single trade by (Id, UserId). UserId leads
            // the composite index because it is the tenant boundary predicate applied on every single query
            // (see EngineTradeEntity.UserId doc comment), while Status is the next most common co-filter.
            entity.HasIndex(e => new { e.UserId, e.Status });

            // Prevents the same user from accepting the same proposal twice (see the read-then-write check in
            // TradeLifecycleService.CreateTradeFromProposalAsync, which is not atomic under concurrent requests).
            // Partial index: manually created trades (Task "manual trade creation") all carry
            // ProposalId == Guid.Empty, which is not a real proposal, so those rows are deliberately excluded
            // from uniqueness — otherwise every user would be limited to a single manual trade ever.
            entity.HasIndex(e => new { e.UserId, e.ProposalId })
                .IsUnique()
                .HasFilter("\"ProposalId\" <> '00000000-0000-0000-0000-000000000000'");

            entity.Property(e => e.ExitPlan)
                .HasColumnType("jsonb")
                .HasConversion(exitPlanConverter);

            entity.HasMany(e => e.Fills)
                .WithOne(f => f.Trade)
                .HasForeignKey(f => f.TradeId)
                .OnDelete(DeleteBehavior.Cascade);
        });

        // 5. Trade Fills Table
        modelBuilder.Entity<EngineTradeFillEntity>(entity =>
        {
            entity.HasKey(e => e.Id);
            entity.HasIndex(e => new { e.TradeId, e.ExecutedAtUtc });
        });

        // 6. Snapshots Table
        modelBuilder.Entity<EngineEvaluationSnapshotEntity>(entity =>
        {
            entity.HasKey(e => e.Id);
            entity.HasIndex(e => new { e.Isin, e.EvaluatedAtUtc });
            entity.HasIndex(e => e.CompositeOpportunityScore);

            // Every admin evaluation-history query (AdminEvaluationHistoryController /
            // EngineGetEvaluationHistory) orders by EvaluatedAtUtc and optionally filters on OutcomeReason
            // and/or TriggerSource, so those are indexed alongside the timestamp rather than on their own.
            entity.HasIndex(e => new { e.OutcomeReason, e.EvaluatedAtUtc });
            entity.HasIndex(e => new { e.TriggerSource, e.EvaluatedAtUtc });

            // Without this, EF Core's migration for this new column would fall back to bool's CLR default
            // (false) for every pre-existing row - which would make old rows read as "simulation vetoed" even
            // though this gate simply did not exist yet for them. true matches PassedSimulationVeto's own
            // C# property default (and ScoringResult's), the more honest "not vetoed" reading for old data.
            entity.Property(e => e.PassedSimulationVeto).HasDefaultValue(true);

            // Same reasoning as PassedSimulationVeto above: pre-existing rows must read as "gate not evaluated
            // / not blocked" rather than fabricating a "blocked" reading for a gate that did not exist yet.
            entity.Property(e => e.PassedDividendGate).HasDefaultValue(true);
        });

        // 7. Scan Cycles Table (Task 3: minimal visibility into the engine-side candidate set per poller cycle)
        modelBuilder.Entity<EngineScanCycleEntity>(entity =>
        {
            entity.HasKey(e => e.Id);
            entity.HasIndex(e => e.CycleStartedAtUtc);

            entity.Property(e => e.CandidateIsins)
                .HasColumnType("jsonb")
                .HasConversion(stringListConverter, stringListComparer);
        });
    }
}

public class EngineDbContextFactory : IDesignTimeDbContextFactory<EngineDbContext>
{
    public EngineDbContext CreateDbContext(string[] args)
    {
        var optionsBuilder = new DbContextOptionsBuilder<EngineDbContext>();
        optionsBuilder.UseNpgsql("Host=localhost;Database=finlytic_engine;Username=postgres;Password=postgres");
        return new EngineDbContext(optionsBuilder.Options);
    }
}