using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Infrastructure;
using Microsoft.EntityFrameworkCore.Migrations;

namespace ClaudeDo.Data.Tests;

/// <summary>
/// AddTaskDependencies moves every <c>tasks.depends_on_task_id</c> value into the new
/// <c>task_dependencies</c> table and then drops the column. Runs a real <c>Migrate()</c> — the
/// EnsureCreated fixtures every other Data.Tests file uses skip migrations entirely and would
/// never notice a data copy that silently dropped rows (see
/// <c>.claudedo/traps/ef-migration-parallel-designer-collision.md</c>).
/// </summary>
public sealed class TaskDependencyMigrationTests : IDisposable
{
    private const string PreviousMigrationId = "20260902102003_AddExpectsNoDiff";

    private readonly string _dbPath;
    private readonly DbContextOptions<ClaudeDoDbContext> _options;

    public TaskDependencyMigrationTests()
    {
        _dbPath = Path.Combine(Path.GetTempPath(), $"claudedo_deps_{Guid.NewGuid():N}.db");
        _options = new DbContextOptionsBuilder<ClaudeDoDbContext>()
            .UseSqlite($"Data Source={_dbPath}")
            .Options;
    }

    public void Dispose()
    {
        Microsoft.Data.Sqlite.SqliteConnection.ClearAllPools();
        foreach (var suffix in new[] { "", "-wal", "-shm" })
            try { File.Delete(_dbPath + suffix); } catch { }
    }

    [Fact]
    public void Existing_depends_on_links_survive_as_one_element_sets()
    {
        SeedLegacyDatabase();

        using (var ctx = new ClaudeDoDbContext(_options))
            ctx.Database.Migrate();

        using var check = new ClaudeDoDbContext(_options);
        Assert.Empty(check.Database.GetPendingMigrations());

        var edges = check.TaskDependencies.AsNoTracking()
            .OrderBy(d => d.TaskId)
            .Select(d => new { d.TaskId, d.DependsOnTaskId })
            .ToList();
        Assert.Equal(2, edges.Count);
        Assert.Equal(("t2", "t1"), (edges[0].TaskId, edges[0].DependsOnTaskId));
        Assert.Equal(("t3", "t2"), (edges[1].TaskId, edges[1].DependsOnTaskId));

        // The tasks themselves are untouched, and the independent one gained no edge.
        Assert.Equal(4, check.Tasks.Count());
        Assert.DoesNotContain("t4", edges.Select(e => e.TaskId));
    }

    [Fact]
    public void Column_is_gone_after_the_migration()
    {
        SeedLegacyDatabase();

        using var ctx = new ClaudeDoDbContext(_options);
        ctx.Database.Migrate();

        var conn = ctx.Database.GetDbConnection();
        conn.Open();
        using var cmd = conn.CreateCommand();
        cmd.CommandText = "SELECT COUNT(*) FROM pragma_table_info('tasks') WHERE name = 'depends_on_task_id'";
        Assert.Equal(0L, Convert.ToInt64(cmd.ExecuteScalar()));
        conn.Close();
    }

    // Migrates *to* the migration before this one, then seeds via raw SQL: EnsureCreated would
    // build today's schema (no depends_on_task_id column at all), so there'd be nothing to copy.
    private void SeedLegacyDatabase()
    {
        using var seed = new ClaudeDoDbContext(_options);
        seed.Database.GetService<IMigrator>().Migrate(PreviousMigrationId);

        var conn = seed.Database.GetDbConnection();
        conn.Open();
        using var cmd = conn.CreateCommand();
        cmd.CommandText = """
            INSERT INTO lists (id, name, created_at) VALUES ('l1', 'List', '2026-01-01 00:00:00');
            INSERT INTO tasks (id, number, list_id, title, status, created_at)
            VALUES ('t1', 1, 'l1', 'first', 'done', '2026-01-01 00:00:00');
            INSERT INTO tasks (id, number, list_id, title, status, created_at, depends_on_task_id)
            VALUES ('t2', 2, 'l1', 'second', 'queued', '2026-01-01 00:00:00', 't1');
            INSERT INTO tasks (id, number, list_id, title, status, created_at, depends_on_task_id)
            VALUES ('t3', 3, 'l1', 'third', 'queued', '2026-01-01 00:00:00', 't2');
            INSERT INTO tasks (id, number, list_id, title, status, created_at)
            VALUES ('t4', 4, 'l1', 'independent', 'idle', '2026-01-01 00:00:00');
            """;
        cmd.ExecuteNonQuery();
        conn.Close();
    }
}