package db

import (
	"context"
	"testing"
)

// documentMigrationID 是文档引用列的迁移 id（design/24 §2.4）。
const documentMigrationID = "0015_chat_message_document"

// TestMigrateDocumentColumnReversible 验证 0015（chat_messages.document，文档
// 引用列）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 TestMigrateDocumentColumnReversible(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", "document") {
		t.Fatal("chat_messages.document 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", "document") {
		t.Fatal("chat_messages.document should still exist after idempotent re-run")
	}

	// 恰好回滚到 0015（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 == documentMigrationID {
			idx = i
		}
	}
	if idx < 0 {
		t.Fatalf("%s not found in %v", documentMigrationID, 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", "document") {
		t.Fatal("chat_messages.document should be dropped by the 0015 down")
	}

	// 重新 up 恢复端到端可用：默认空串意味着「这条消息没有附件」。
	if err := MigrateUp(ctx, conn, testLogger()); err != nil {
		t.Fatalf("re-MigrateUp: %v", err)
	}
	if !columnExists(t, ctx, conn, "chat_messages", "document") {
		t.Fatal("chat_messages.document 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 document: %v", err)
	}
	var doc string
	if err := conn.QueryRowContext(ctx, `SELECT document FROM chat_messages WHERE id = ?`, "m1").Scan(&doc); err != nil {
		t.Fatalf("select document: %v", err)
	}
	if doc != "" {
		t.Fatalf("document = %q, want the empty default", doc)
	}
}