package db

import (
	"context"
	"testing"
)

// turnIDMigrationID 是回合标识列的迁移 id（design/15 §2.5.9）。
const turnIDMigrationID = "0018_chat_message_turn_id"

// TestMigrateTurnIDColumnReversible 验证 0018（chat_messages.turn_id，回合标识列）
// 可上下翻滚：up 建列、重复 up 是空操作、down 删列、再 up 恢复。它用自己的内存库，
// 绝不碰 data/cyrene.db。
func TestMigrateTurnIDColumnReversible(t *testing.T) {
	t.Parallel()
	ctx := context.Background()
	conn := openMemory(t)

	if err := MigrateUp(ctx, conn, testLogger()); err != nil {
		t.Fatalf("MigrateUp: %v", err)
	}
	if !columnExists(t, ctx, conn, "chat_messages", "turn_id") {
		t.Fatal("chat_messages.turn_id should exist after MigrateUp")
	}

	// 重复 up：已记录的迁移被跳过，列仍在且不报错（幂等）。
	if err := MigrateUp(ctx, conn, testLogger()); err != nil {
		t.Fatalf("MigrateUp second call: %v", err)
	}
	if !columnExists(t, ctx, conn, "chat_messages", "turn_id") {
		t.Fatal("chat_messages.turn_id should still exist after idempotent re-run")
	}

	// 恰好回滚到 0018（含它之后新加的迁移），因此日后再加迁移也不会让本测试失效。
	ids := upMigrationIDs(t)
	idx := -1
	for i, id := range ids {
		if id == turnIDMigrationID {
			idx = i
		}
	}
	if idx < 0 {
		t.Fatalf("%s not found in %v", turnIDMigrationID, ids)
	}
	if err := MigrateDown(ctx, conn, len(ids)-idx, testLogger()); err != nil {
		t.Fatalf("MigrateDown(%d): %v", len(ids)-idx, err)
	}
	if columnExists(t, ctx, conn, "chat_messages", "turn_id") {
		t.Fatal("chat_messages.turn_id should be dropped by the 0018 down")
	}

	// 重新 up 恢复端到端可用：默认空串意味着「这一行不属于任何已知回合」。
	if err := MigrateUp(ctx, conn, testLogger()); err != nil {
		t.Fatalf("re-MigrateUp: %v", err)
	}
	if !columnExists(t, ctx, conn, "chat_messages", "turn_id") {
		t.Fatal("chat_messages.turn_id should exist again after re-MigrateUp")
	}
	if _, err := conn.ExecContext(ctx,
		`INSERT INTO chat_messages (id, session_id, role, content, created_at) VALUES (?, ?, ?, ?, ?)`,
		"m1", "web", "user", "hi", 1000); err != nil {
		t.Fatalf("insert without turn id: %v", err)
	}
	var turnID string
	if err := conn.QueryRowContext(ctx, `SELECT turn_id FROM chat_messages WHERE id = ?`, "m1").Scan(&turnID); err != nil {
		t.Fatalf("select turn_id: %v", err)
	}
	if turnID != "" {
		t.Fatalf("turn_id = %q, want the empty default", turnID)
	}
}