using Xunit;
using Npgsql;
using NpgsqlTypes;
using System.Data;
using System.Data.Common;

namespace KArtSell.Integration.Tests;

/// <summary>
/// DbUp Migration Validation Tests
/// Covers: Fresh Install, Idempotency, Schema Validation, Trigger/Constraint Enforcement
/// Following AGENTS.md v16.0: Necessity-driven, Complete evidence preservation, Reproducible
/// </summary>
public sealed class DbUpMigrationTests : IAsyncLifetime
{
    private NpgsqlDataSource _dataSource = null!;
    private const string DefaultConnString = "Host=localhost;Port=5432;Database=kartsell_migration_test;Username=kartsell;Password=kartsell";

    public async Task InitializeAsync()
    {
        var connString = TestDatabaseConnection.GetConnectionString();

        // Create test database if needed
        var adminConnString = connString.Replace("kartsell_migration_test", "postgres");
        await using var adminConn = new NpgsqlConnection(adminConnString);
        await adminConn.OpenAsync();

        try
        {
            await using var cmd = adminConn.CreateCommand();
            cmd.CommandText = "DROP DATABASE IF EXISTS kartsell_migration_test WITH (FORCE);";
            await cmd.ExecuteNonQueryAsync();
        }
        catch (PostgresException ex) when (ex.SqlState == "3D000") { /* DB doesn't exist */ }

        await using var createCmd = adminConn.CreateCommand();
        createCmd.CommandText = "CREATE DATABASE kartsell_migration_test;";
        await createCmd.ExecuteNonQueryAsync();

        await adminConn.CloseAsync();

        // Connect to test database
        _dataSource = new NpgsqlDataSourceBuilder(connString).Build();

        // Apply prerequisite migrations (0000-0007)
        await ApplyPrerequisiteMigrationsAsync();
    }

    public async Task DisposeAsync()
    {
        await _dataSource.DisposeAsync();

        // Cleanup test database
        var adminConnString = TestDatabaseConnection.GetConnectionString();
        adminConnString = adminConnString.Replace("kartsell_migration_test", "postgres");

        await using var adminConn = new NpgsqlConnection(adminConnString);
        await adminConn.OpenAsync();

        await using var dropCmd = adminConn.CreateCommand();
        dropCmd.CommandText = "DROP DATABASE IF EXISTS kartsell_migration_test WITH (FORCE);";
        await dropCmd.ExecuteNonQueryAsync();

        await adminConn.CloseAsync();
    }

    /// <summary>
    /// Prerequisite: Apply migrations 0000-0007 to prepare for testing 0008, 0009, 0010
    /// </summary>
    private async Task ApplyPrerequisiteMigrationsAsync()
    {
        await using var connection = await _dataSource.OpenConnectionAsync();

        // Create __dbup_schema_history table
        await using var createHistoryCmd = connection.CreateCommand();
        createHistoryCmd.CommandText = """
            CREATE TABLE IF NOT EXISTS __dbup_schema_history (
                id SERIAL PRIMARY KEY,
                scriptname VARCHAR(255) NOT NULL,
                applied TIMESTAMP NOT NULL DEFAULT NOW()
            );
            """;
        await createHistoryCmd.ExecuteNonQueryAsync();

        // Apply building blocks schema (0000)
        await using var bbCmd = connection.CreateCommand();
        bbCmd.CommandText = """
            CREATE SCHEMA IF NOT EXISTS building_blocks;
            CREATE TABLE IF NOT EXISTS building_blocks.outbox_message (
                id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
                event_type VARCHAR(256) NOT NULL,
                payload JSONB NOT NULL,
                published BOOLEAN DEFAULT FALSE,
                created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
                published_at TIMESTAMP
            );
            CREATE SCHEMA IF NOT EXISTS outbox;
            CREATE TABLE IF NOT EXISTS outbox.outbox (
                id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
                event_type VARCHAR(256) NOT NULL,
                payload JSONB NOT NULL,
                published BOOLEAN DEFAULT FALSE,
                created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
                published_at TIMESTAMP
            );
            """;
        await bbCmd.ExecuteNonQueryAsync();
    }

    /// <summary>
    /// Gate 1: Fresh Install - Migrations run in order with no errors
    /// </summary>
    [Fact]
    public async Task Migration0008_FreshInstall_CreatesValidShadowRunSchema()
    {
        // Act: Apply migration 0008
        await ApplyMigration0008();

        // Assert: Table exists with correct structure
        await using var connection = await _dataSource.OpenConnectionAsync();

        var tableExists = await TableExistsAsync(connection, "model_operations", "shadow_run");
        Assert.True(tableExists, "shadow_run table should exist");

        var columns = await GetTableColumnsAsync(connection, "model_operations", "shadow_run");
        Assert.Contains("run_id", columns);
        Assert.Contains("model_id", columns);
        Assert.Contains("status", columns);
        Assert.Contains("published_at", columns);
        Assert.Contains("metrics_json", columns);
        Assert.Contains("phase_analysis_json", columns);
        Assert.Contains("cost_analysis_json", columns);
        Assert.Contains("false_exit_analysis_json", columns);
        Assert.Contains("validation_gates_json", columns);
    }

    /// <summary>
    /// Gate 1: Fresh Install - All 3 migrations run in sequence
    /// </summary>
    [Fact]
    public async Task Migration0009_0010_FreshInstall_CreatesCompleteSchema()
    {
        // Act: Apply all three migrations
        await ApplyMigration0008();
        await ApplyMigration0009();
        await ApplyMigration0010();

        await using var connection = await _dataSource.OpenConnectionAsync();

        // Assert: All three tables exist
        Assert.True(await TableExistsAsync(connection, "model_operations", "shadow_run"));
        Assert.True(await TableExistsAsync(connection, "building_blocks", "inbox_message"));
        Assert.True(await TableExistsAsync(connection, "model_operations", "approval_queue"));

        // Assert: Foreign keys exist
        var aqFkCount = await CountForeignKeysAsync(connection, "model_operations", "approval_queue");
        Assert.True(aqFkCount > 0, "approval_queue should have FK to shadow_run");
    }

    /// <summary>
    /// Gate 2: Idempotency - Re-running migrations is safe
    /// </summary>
    [Fact]
    public async Task Migration0008_Idempotency_ReRunningIsSafe()
    {
        // Arrange: Apply migration once
        await ApplyMigration0008();

        await using var connection = await _dataSource.OpenConnectionAsync();

        // Insert a test record
        var runId = Guid.NewGuid();
        var modelId = Guid.NewGuid();

        await using var insertCmd = connection.CreateCommand();
        insertCmd.CommandText = """
            INSERT INTO model_operations.shadow_run (run_id, model_id, window_start, window_end, status)
            VALUES (@runId, @modelId, @start, @end, 'Pending');
            """;
        insertCmd.Parameters.AddWithValue("@runId", runId);
        insertCmd.Parameters.AddWithValue("@modelId", modelId);
        insertCmd.Parameters.AddWithValue("@start", new DateOnly(2024, 1, 2));
        insertCmd.Parameters.AddWithValue("@end", new DateOnly(2024, 8, 31));
        await insertCmd.ExecuteNonQueryAsync();

        // Act: Re-run migration
        await ApplyMigration0008();

        // Assert: Data survived, table is unchanged
        await using var selectCmd = connection.CreateCommand();
        selectCmd.CommandText = "SELECT COUNT(*) FROM model_operations.shadow_run WHERE run_id = @runId;";
        selectCmd.Parameters.AddWithValue("@runId", runId);
        var count = (long?)await selectCmd.ExecuteScalarAsync();

        Assert.Equal(1, count);
    }

    /// <summary>
    /// Gate 3: Constraints - Status transitions enforced
    /// </summary>
    [Fact]
    public async Task Migration0008_Constraint_StatusValuesEnforced()
    {
        await ApplyMigration0008();
        await using var connection = await _dataSource.OpenConnectionAsync();

        // Act: Try to insert invalid status
        var runId = Guid.NewGuid();
        var modelId = Guid.NewGuid();

        await using var invalidCmd = connection.CreateCommand();
        invalidCmd.CommandText = """
            INSERT INTO model_operations.shadow_run (run_id, model_id, window_start, window_end, status)
            VALUES (@runId, @modelId, @start, @end, 'InvalidStatus');
            """;
        invalidCmd.Parameters.AddWithValue("@runId", runId);
        invalidCmd.Parameters.AddWithValue("@modelId", modelId);
        invalidCmd.Parameters.AddWithValue("@start", new DateOnly(2024, 1, 2));
        invalidCmd.Parameters.AddWithValue("@end", new DateOnly(2024, 8, 31));

        // Assert: Constraint violation
        await Assert.ThrowsAsync<PostgresException>(
            () => invalidCmd.ExecuteNonQueryAsync());
    }

    /// <summary>
    /// Gate 3: Constraints - Window order enforced (start <= end)
    /// </summary>
    [Fact]
    public async Task Migration0008_Constraint_WindowOrderEnforced()
    {
        await ApplyMigration0008();
        await using var connection = await _dataSource.OpenConnectionAsync();

        // Act: Try to insert with end < start
        var runId = Guid.NewGuid();
        var modelId = Guid.NewGuid();

        await using var invalidCmd = connection.CreateCommand();
        invalidCmd.CommandText = """
            INSERT INTO model_operations.shadow_run (run_id, model_id, window_start, window_end, status)
            VALUES (@runId, @modelId, @start, @end, 'Pending');
            """;
        invalidCmd.Parameters.AddWithValue("@runId", runId);
        invalidCmd.Parameters.AddWithValue("@modelId", modelId);
        invalidCmd.Parameters.AddWithValue("@start", new DateOnly(2024, 8, 31));
        invalidCmd.Parameters.AddWithValue("@end", new DateOnly(2024, 1, 2));

        // Assert: Constraint violation
        await Assert.ThrowsAsync<PostgresException>(
            () => invalidCmd.ExecuteNonQueryAsync());
    }

    /// <summary>
    /// Gate 3: Trigger - Inbox processed_at validation
    /// </summary>
    [Fact]
    public async Task Migration0009_Trigger_InboxProcessedAtRequired()
    {
        await ApplyMigration0008();
        await ApplyMigration0009();

        await using var connection = await _dataSource.OpenConnectionAsync();

        // Insert outbox message first
        var outboxId = Guid.NewGuid();
        await using var outboxCmd = connection.CreateCommand();
        outboxCmd.CommandText = """
            INSERT INTO building_blocks.outbox_message
                (message_id, event_type, schema_version, payload_json, correlation_id, occurred_at, payload_hash)
            VALUES (@id, 'TestEvent', 1, '{"test":"data"}'::jsonb, 'test-correlation', CURRENT_TIMESTAMP, 'test-hash');
            """;
        outboxCmd.Parameters.AddWithValue("@id", outboxId);
        await outboxCmd.ExecuteNonQueryAsync();

        // Act: Try to set status=Processed without processed_at
        var inboxId = Guid.NewGuid();
        await using var invalidCmd = connection.CreateCommand();
        invalidCmd.CommandText = """
            INSERT INTO building_blocks.inbox_message (message_id, consumer, status)
            VALUES (@id, 'TestConsumer', 'Processed');
            """;
        invalidCmd.Parameters.AddWithValue("@id", inboxId);

        // Assert: Trigger violation
        await Assert.ThrowsAsync<PostgresException>(
            () => invalidCmd.ExecuteNonQueryAsync());
    }

    /// <summary>
    /// Gate 3: Idempotency - Inbox dedup constraint
    /// </summary>
    [Fact]
    public async Task Migration0009_Constraint_InboxIdempotencyEnforced()
    {
        await ApplyMigration0008();
        await ApplyMigration0009();

        await using var connection = await _dataSource.OpenConnectionAsync();

        // Insert outbox message
        var outboxId = Guid.NewGuid();
        await using var outboxCmd = connection.CreateCommand();
        outboxCmd.CommandText = """
            INSERT INTO building_blocks.outbox_message
                (message_id, event_type, schema_version, payload_json, correlation_id, occurred_at, payload_hash)
            VALUES (@id, 'TestEvent', 1, '{"test":"data"}'::jsonb, 'test-correlation', CURRENT_TIMESTAMP, 'test-hash');
            """;
        outboxCmd.Parameters.AddWithValue("@id", outboxId);
        await outboxCmd.ExecuteNonQueryAsync();

        // Insert first inbox record
        await using var insertCmd = connection.CreateCommand();
        insertCmd.CommandText = """
            INSERT INTO building_blocks.inbox_message (message_id, consumer, status)
            VALUES (@outboxId, 'Consumer1', 'Pending');
            """;
        insertCmd.Parameters.AddWithValue("@outboxId", outboxId);
        await insertCmd.ExecuteNonQueryAsync();

        // Act: Try to insert duplicate (same outbox_id + consumer_id)
        await using var duplicateCmd = connection.CreateCommand();
        duplicateCmd.CommandText = """
            INSERT INTO building_blocks.inbox_message (message_id, consumer, status)
            VALUES (@outboxId, 'Consumer1', 'Pending');
            """;
        duplicateCmd.Parameters.AddWithValue("@outboxId", outboxId);

        // Assert: UNIQUE constraint violation
        await Assert.ThrowsAsync<PostgresException>(
            () => duplicateCmd.ExecuteNonQueryAsync());
    }

    /// <summary>
    /// Gate 3: Trigger - Approval workflow validation
    /// </summary>
    [Fact]
    public async Task Migration0010_Trigger_ApprovalRequiresApprovedBy()
    {
        await ApplyMigration0008();
        await ApplyMigration0010();

        await using var connection = await _dataSource.OpenConnectionAsync();

        // Insert shadow_run first
        var runId = Guid.NewGuid();
        var modelId = Guid.NewGuid();
        await using var srCmd = connection.CreateCommand();
        srCmd.CommandText = """
            INSERT INTO model_operations.shadow_run (run_id, model_id, window_start, window_end, status)
            VALUES (@runId, @modelId, @start, @end, 'Pending');
            """;
        srCmd.Parameters.AddWithValue("@runId", runId);
        srCmd.Parameters.AddWithValue("@modelId", modelId);
        srCmd.Parameters.AddWithValue("@start", new DateOnly(2024, 1, 2));
        srCmd.Parameters.AddWithValue("@end", new DateOnly(2024, 8, 31));
        await srCmd.ExecuteNonQueryAsync();

        // Act: Try to set status=Approved without approved_by
        await using var invalidCmd = connection.CreateCommand();
        invalidCmd.CommandText = """
            INSERT INTO model_operations.approval_queue (run_id, model_id, status)
            VALUES (@runId, @modelId, 'Approved');
            """;
        invalidCmd.Parameters.AddWithValue("@runId", runId);
        invalidCmd.Parameters.AddWithValue("@modelId", modelId);

        // Assert: Trigger violation
        await Assert.ThrowsAsync<PostgresException>(
            () => invalidCmd.ExecuteNonQueryAsync());
    }

    /// <summary>
    /// Gate 3: Trigger - Rejection requires reason
    /// </summary>
    [Fact]
    public async Task Migration0010_Trigger_RejectionRequiresReason()
    {
        await ApplyMigration0008();
        await ApplyMigration0010();

        await using var connection = await _dataSource.OpenConnectionAsync();

        // Insert shadow_run
        var runId = Guid.NewGuid();
        var modelId = Guid.NewGuid();
        await using var srCmd = connection.CreateCommand();
        srCmd.CommandText = """
            INSERT INTO model_operations.shadow_run (run_id, model_id, window_start, window_end, status)
            VALUES (@runId, @modelId, @start, @end, 'Pending');
            """;
        srCmd.Parameters.AddWithValue("@runId", runId);
        srCmd.Parameters.AddWithValue("@modelId", modelId);
        srCmd.Parameters.AddWithValue("@start", new DateOnly(2024, 1, 2));
        srCmd.Parameters.AddWithValue("@end", new DateOnly(2024, 8, 31));
        await srCmd.ExecuteNonQueryAsync();

        // Act: Try to set status=Rejected without rejection_reason
        await using var invalidCmd = connection.CreateCommand();
        invalidCmd.CommandText = """
            INSERT INTO model_operations.approval_queue (run_id, model_id, status)
            VALUES (@runId, @modelId, 'Rejected');
            """;
        invalidCmd.Parameters.AddWithValue("@runId", runId);
        invalidCmd.Parameters.AddWithValue("@modelId", modelId);

        // Assert: Trigger violation
        await Assert.ThrowsAsync<PostgresException>(
            () => invalidCmd.ExecuteNonQueryAsync());
    }

    /// <summary>
    /// Gate 4: Failure Recovery - FK constraint prevents orphaned approvals
    /// </summary>
    [Fact]
    public async Task Migration0010_ForeignKey_PreventsShadowRunDeletion()
    {
        await ApplyMigration0008();
        await ApplyMigration0010();

        await using var connection = await _dataSource.OpenConnectionAsync();

        // Insert shadow_run and approval
        var runId = Guid.NewGuid();
        var modelId = Guid.NewGuid();
        var approverId = Guid.NewGuid();

        await using var srCmd = connection.CreateCommand();
        srCmd.CommandText = """
            INSERT INTO model_operations.shadow_run (run_id, model_id, window_start, window_end, status)
            VALUES (@runId, @modelId, @start, @end, 'Pending');
            """;
        srCmd.Parameters.AddWithValue("@runId", runId);
        srCmd.Parameters.AddWithValue("@modelId", modelId);
        srCmd.Parameters.AddWithValue("@start", new DateOnly(2024, 1, 2));
        srCmd.Parameters.AddWithValue("@end", new DateOnly(2024, 8, 31));
        await srCmd.ExecuteNonQueryAsync();

        await using var aqCmd = connection.CreateCommand();
        aqCmd.CommandText = """
            INSERT INTO model_operations.approval_queue (run_id, model_id, status, approved_by, approval_reason)
            VALUES (@runId, @modelId, 'Approved', @approverId, 'Test approval');
            """;
        aqCmd.Parameters.AddWithValue("@runId", runId);
        aqCmd.Parameters.AddWithValue("@modelId", modelId);
        aqCmd.Parameters.AddWithValue("@approverId", approverId);
        await aqCmd.ExecuteNonQueryAsync();

        // Act: Try to delete shadow_run (should fail due to FK)
        await using var deleteCmd = connection.CreateCommand();
        deleteCmd.CommandText = "DELETE FROM model_operations.shadow_run WHERE run_id = @runId;";
        deleteCmd.Parameters.AddWithValue("@runId", runId);

        // Assert: FK violation prevents deletion
        await Assert.ThrowsAsync<PostgresException>(
            () => deleteCmd.ExecuteNonQueryAsync());
    }

    /// <summary>
    /// Gate 4: Indexes - Common queries are indexed
    /// </summary>
    [Fact]
    public async Task Migration0008_Indexes_ExistForCommonQueries()
    {
        await ApplyMigration0008();
        await using var connection = await _dataSource.OpenConnectionAsync();

        var indexes = await GetIndexesAsync(connection, "model_operations", "shadow_run");

        Assert.Contains("idx_shadow_run_model_created", indexes);
        Assert.Contains("idx_shadow_run_status", indexes);
        Assert.Contains("idx_shadow_run_published_at", indexes);
    }

    // ========== Helpers ==========

    private async Task ApplyMigration0008()
    {
        await using var connection = await _dataSource.OpenConnectionAsync();
        await using var cmd = connection.CreateCommand();
        cmd.CommandText = File.ReadAllText(Path.Combine(AppContext.BaseDirectory, "migrations", "0022_model_operations_execution_schema.sql"));
        await cmd.ExecuteNonQueryAsync();
    }

    private async Task ApplyMigration0009()
    {
        await using var connection = await _dataSource.OpenConnectionAsync();
        await using var cmd = connection.CreateCommand();
        cmd.CommandText = File.ReadAllText(Path.Combine(AppContext.BaseDirectory, "migrations", "0023_inbox_status_contract.sql"));
        await cmd.ExecuteNonQueryAsync();
    }

    private async Task ApplyMigration0010()
    {
        await using var connection = await _dataSource.OpenConnectionAsync();
        await using var cmd = connection.CreateCommand();
        cmd.CommandText = File.ReadAllText(Path.Combine(AppContext.BaseDirectory, "migrations", "0022_model_operations_execution_schema.sql"));
        await cmd.ExecuteNonQueryAsync();
    }

    private static async Task<bool> TableExistsAsync(DbConnection connection, string schema, string table)
    {
        await using var cmd = connection.CreateCommand();
        cmd.CommandText = """
            SELECT EXISTS (
                SELECT 1 FROM information_schema.tables
                WHERE table_schema = @schema AND table_name = @table
            );
            """;
        cmd.Parameters.Add(new NpgsqlParameter("@schema", schema));
        cmd.Parameters.Add(new NpgsqlParameter("@table", table));

        var result = await cmd.ExecuteScalarAsync();
        return result is true or (long)1;
    }

    private static async Task<List<string>> GetTableColumnsAsync(DbConnection connection, string schema, string table)
    {
        await using var cmd = connection.CreateCommand();
        cmd.CommandText = """
            SELECT column_name FROM information_schema.columns
            WHERE table_schema = @schema AND table_name = @table
            ORDER BY ordinal_position;
            """;
        cmd.Parameters.Add(new NpgsqlParameter("@schema", schema));
        cmd.Parameters.Add(new NpgsqlParameter("@table", table));

        var columns = new List<string>();
        await using var reader = await cmd.ExecuteReaderAsync();
        while (await reader.ReadAsync())
        {
            columns.Add(reader.GetString(0));
        }
        return columns;
    }

    private static async Task<int> CountForeignKeysAsync(DbConnection connection, string schema, string table)
    {
        await using var cmd = connection.CreateCommand();
        cmd.CommandText = """
            SELECT COUNT(*) FROM information_schema.table_constraints
            WHERE table_schema = @schema AND table_name = @table
            AND constraint_type = 'FOREIGN KEY';
            """;
        cmd.Parameters.Add(new NpgsqlParameter("@schema", schema));
        cmd.Parameters.Add(new NpgsqlParameter("@table", table));

        var result = await cmd.ExecuteScalarAsync();
        return Convert.ToInt32(result);
    }

    private static async Task<List<string>> GetIndexesAsync(DbConnection connection, string schema, string table)
    {
        await using var cmd = connection.CreateCommand();
        cmd.CommandText = """
            SELECT indexname FROM pg_indexes
            WHERE schemaname = @schema AND tablename = @table;
            """;
        cmd.Parameters.Add(new NpgsqlParameter("@schema", schema));
        cmd.Parameters.Add(new NpgsqlParameter("@table", table));

        var indexes = new List<string>();
        await using var reader = await cmd.ExecuteReaderAsync();
        while (await reader.ReadAsync())
        {
            indexes.Add(reader.GetString(0));
        }
        return indexes;
    }
}