// Copyright 2026 The Xorm Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package xorm

import (
	"testing"

	"github.com/stretchr/testify/assert"
	"xorm.io/xorm/schemas"
)

func newTestIndex(name string, indexType int, cols ...string) *schemas.Index {
	index := schemas.NewIndex(name, indexType)
	index.AddColumn(cols...)
	return index
}

func indexMap(indexes ...*schemas.Index) map[string]*schemas.Index {
	m := make(map[string]*schemas.Index, len(indexes))
	for _, index := range indexes {
		m[index.Name] = index
	}
	return m
}

func TestMatchIndexes(t *testing.T) {
	for _, tc := range []struct {
		name        string
		expected    map[string]*schemas.Index
		existing    map[string]*schemas.Index
		wantClaimed []string
		wantMissing []string
	}{
		{
			name: "same definition, both exist",
			expected: indexMap(
				newTestIndex("first", schemas.IndexType, "repo_id", "created_at"),
				newTestIndex("second", schemas.IndexType, "repo_id", "created_at"),
			),
			existing: indexMap(
				newTestIndex("first", schemas.IndexType, "repo_id", "created_at"),
				newTestIndex("second", schemas.IndexType, "repo_id", "created_at"),
			),
			wantClaimed: []string{"first", "second"},
		},
		{
			name: "same definition, first missing",
			expected: indexMap(
				newTestIndex("first", schemas.IndexType, "repo_id", "created_at"),
				newTestIndex("second", schemas.IndexType, "repo_id", "created_at"),
			),
			existing: indexMap(
				newTestIndex("second", schemas.IndexType, "repo_id", "created_at"),
			),
			wantClaimed: []string{"second"},
			wantMissing: []string{"first"},
		},
		{
			name: "same definition, second missing",
			expected: indexMap(
				newTestIndex("first", schemas.IndexType, "repo_id", "created_at"),
				newTestIndex("second", schemas.IndexType, "repo_id", "created_at"),
			),
			existing: indexMap(
				newTestIndex("first", schemas.IndexType, "repo_id", "created_at"),
			),
			wantClaimed: []string{"first"},
			wantMissing: []string{"second"},
		},
		{
			name: "same columns in different order",
			expected: indexMap(
				newTestIndex("c_u", schemas.IndexType, "user_id", "is_deleted", "created_unix"),
				newTestIndex("c_u_d", schemas.IndexType, "created_unix", "user_id", "is_deleted"),
			),
			existing: indexMap(
				newTestIndex("c_u_d", schemas.IndexType, "created_unix", "user_id", "is_deleted"),
			),
			wantClaimed: []string{"c_u_d"},
			wantMissing: []string{"c_u"},
		},
		{
			name:        "renamed index keeps the existing one",
			expected:    indexMap(newTestIndex("new_name", schemas.IndexType, "repo_id")),
			existing:    indexMap(newTestIndex("old_name", schemas.IndexType, "repo_id")),
			wantClaimed: []string{"old_name"},
		},
		{
			name:        "changed definition under the same name",
			expected:    indexMap(newTestIndex("repo", schemas.IndexType, "repo_id", "created_at")),
			existing:    indexMap(newTestIndex("repo", schemas.IndexType, "created_at", "repo_id")),
			wantMissing: []string{"repo"},
		},
		{
			name:        "index turned into a unique",
			expected:    indexMap(newTestIndex("repo", schemas.UniqueType, "repo_id")),
			existing:    indexMap(newTestIndex("repo", schemas.IndexType, "repo_id")),
			wantMissing: []string{"repo"},
		},
		{
			name: "same name wins over a renamed duplicate",
			expected: indexMap(
				newTestIndex("first", schemas.IndexType, "repo_id"),
				newTestIndex("second", schemas.IndexType, "repo_id"),
			),
			existing: indexMap(
				newTestIndex("legacy", schemas.IndexType, "repo_id"),
				newTestIndex("second", schemas.IndexType, "repo_id"),
			),
			wantClaimed: []string{"legacy", "second"},
		},
		{
			name: "existing index is claimed only once",
			expected: indexMap(
				newTestIndex("a", schemas.IndexType, "repo_id"),
				newTestIndex("b", schemas.IndexType, "repo_id"),
			),
			existing:    indexMap(newTestIndex("legacy", schemas.IndexType, "repo_id")),
			wantClaimed: []string{"legacy"},
			wantMissing: []string{"b"},
		},
		{
			name:     "stale index is left unclaimed",
			expected: indexMap(newTestIndex("repo", schemas.IndexType, "repo_id")),
			existing: indexMap(
				newTestIndex("repo", schemas.IndexType, "repo_id"),
				newTestIndex("stale", schemas.IndexType, "owner_id"),
			),
			wantClaimed: []string{"repo"},
		},
	} {
		t.Run(tc.name, func(t *testing.T) {
			for i := 0; i < 20; i++ {
				claimed, missing := matchIndexes(tc.expected, tc.existing)

				var claimedNames []string
				for name, ok := range claimed {
					if ok {
						claimedNames = append(claimedNames, name)
					}
				}
				assert.ElementsMatch(t, tc.wantClaimed, claimedNames)
				assert.ElementsMatch(t, tc.wantMissing, sortedIndexNames(missing))
			}
		})
	}
}