ClaudeDo/src/ClaudeDo.Data/Migrations/20260902121712_AddTaskDependencies.cs

using Microsoft.EntityFrameworkCore.Migrations;

#nullable disable

namespace ClaudeDo.Data.Migrations
{
    /// <summary>
    /// Turns the single <c>tasks.depends_on_task_id</c> column into a set: one row per declared
    /// "run after" edge in <c>task_dependencies</c>. Hand-edited after scaffolding so the data copy
    /// sits between CreateTable and DropColumn — the scaffolded order dropped the column first and
    /// would have discarded every existing link.
    /// </summary>
    public partial class AddTaskDependencies : Migration
    {
        /// <inheritdoc />
        protected override void Up(MigrationBuilder migrationBuilder)
        {
            migrationBuilder.CreateTable(
                name: "task_dependencies",
                columns: table => new
                {
                    task_id = table.Column<string>(type: "TEXT", nullable: false),
                    depends_on_task_id = table.Column<string>(type: "TEXT", nullable: false)
                },
                constraints: table =>
                {
                    table.PrimaryKey("PK_task_dependencies", x => new { x.task_id, x.depends_on_task_id });
                    table.ForeignKey(
                        name: "FK_task_dependencies_tasks_depends_on_task_id",
                        column: x => x.depends_on_task_id,
                        principalTable: "tasks",
                        principalColumn: "id",
                        onDelete: ReferentialAction.Cascade);
                    table.ForeignKey(
                        name: "FK_task_dependencies_tasks_task_id",
                        column: x => x.task_id,
                        principalTable: "tasks",
                        principalColumn: "id",
                        onDelete: ReferentialAction.Cascade);
                });

            migrationBuilder.CreateIndex(
                name: "idx_task_dependencies_depends_on",
                table: "task_dependencies",
                column: "depends_on_task_id");

            // Every existing link becomes a one-element set. The old FK was ON DELETE SET NULL, so
            // a surviving value always points at an existing task and can't violate the new FK.
            migrationBuilder.Sql("""
                INSERT INTO task_dependencies (task_id, depends_on_task_id)
                SELECT id, depends_on_task_id FROM tasks WHERE depends_on_task_id IS NOT NULL
                """);

            migrationBuilder.DropForeignKey(
                name: "FK_tasks_tasks_depends_on_task_id",
                table: "tasks");

            migrationBuilder.DropIndex(
                name: "idx_tasks_depends_on",
                table: "tasks");

            migrationBuilder.DropColumn(
                name: "depends_on_task_id",
                table: "tasks");
        }

        /// <inheritdoc />
        protected override void Down(MigrationBuilder migrationBuilder)
        {
            migrationBuilder.AddColumn<string>(
                name: "depends_on_task_id",
                table: "tasks",
                type: "TEXT",
                nullable: true);

            // Inherently lossy: a task with several predecessors keeps only one. There is no
            // single-column shape that could hold the rest.
            migrationBuilder.Sql("""
                UPDATE tasks SET depends_on_task_id = (
                    SELECT td.depends_on_task_id FROM task_dependencies td
                    WHERE td.task_id = tasks.id
                    ORDER BY td.depends_on_task_id
                    LIMIT 1
                )
                """);

            migrationBuilder.DropTable(
                name: "task_dependencies");

            migrationBuilder.CreateIndex(
                name: "idx_tasks_depends_on",
                table: "tasks",
                column: "depends_on_task_id");

            migrationBuilder.AddForeignKey(
                name: "FK_tasks_tasks_depends_on_task_id",
                table: "tasks",
                column: "depends_on_task_id",
                principalTable: "tasks",
                principalColumn: "id",
                onDelete: ReferentialAction.SetNull);
        }
    }
}