// Vikunja is a to-do list application to facilitate your life.
// Copyright 2018-present Vikunja and contributors. All rights reserved.
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

package models

import (
	"testing"

	"code.vikunja.io/api/pkg/db"
	"code.vikunja.io/api/pkg/user"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

func TestKanbanViewBucketFiltering(t *testing.T) {
	db.LoadAndAssertFixtures(t)
	s := db.NewSession()
	defer s.Close()

	view, err := GetProjectViewByID(s, 4)
	require.NoError(t, err)

	project, err := GetProjectSimpleByID(s, view.ProjectID)
	require.NoError(t, err)

	buckets, err := GetTasksInBucketsForView(s, view, []*Project{project}, &taskSearchOptions{}, &user.User{ID: 1})
	require.NoError(t, err)

	taskBuckets := map[int64][]int64{}
	for _, b := range buckets {
		for _, tsk := range b.Tasks {
			taskBuckets[tsk.ID] = append(taskBuckets[tsk.ID], b.ID)
		}
	}

	for tid, bs := range taskBuckets {
		assert.Lenf(t, bs, 1, "task %d appears in multiple buckets: %v", tid, bs)
	}

	for _, id := range []int64{40, 41, 42, 43, 44, 45, 46} {
		assert.NotContains(t, taskBuckets, id)
	}
}

// TestTaskSearchRelevanceRanking verifies that a multi-word search ranks the task
// matching all words above tasks matching only some. The ranking is BM25-based and
// therefore only enforced on ParadeDB; on other databases we only assert that the
// matching tasks are returned (no order guarantee), keeping the test green across
// the whole CI database matrix.
func TestTaskSearchRelevanceRanking(t *testing.T) {
	db.LoadAndAssertFixtures(t)
	s := db.NewSession()
	defer s.Close()

	usr := &user.User{ID: 1}

	allWords := &Task{Title: "Backup server migration", ProjectID: 1}
	require.NoError(t, allWords.Create(s, usr))
	oneWordA := &Task{Title: "Backup of old files", ProjectID: 1}
	require.NoError(t, oneWordA.Create(s, usr))
	oneWordB := &Task{Title: "server room booking", ProjectID: 1}
	require.NoError(t, oneWordB.Create(s, usr))

	assertRelevanceRanked := func(t *testing.T, tc *TaskCollection) {
		got, _, _, err := tc.ReadAll(s, usr, "backup server", 0, 50)
		require.NoError(t, err)

		gotTasks, is := got.([]*Task)
		require.True(t, is)

		gotIDs := make([]int64, len(gotTasks))
		for i, tsk := range gotTasks {
			gotIDs[i] = tsk.ID
		}

		require.Contains(t, gotIDs, allWords.ID, "the task matching all words should be returned")

		if db.ParadeDBAvailable() {
			require.NotEmpty(t, gotTasks)
			assert.Equal(t, allWords.ID, gotTasks[0].ID, "task matching all query words should rank first by BM25 relevance")
		}
	}

	// Without a view: plain "tasks.*, pdb.score(tasks.id)" select.
	t.Run("no view", func(t *testing.T) {
		assertRelevanceRanked(t, &TaskCollection{ProjectID: 1})
	})

	// With a view: exercises the task_positions LEFT JOIN, which adds
	// task_positions.position to the DISTINCT select alongside pdb.score(tasks.id).
	t.Run("list view", func(t *testing.T) {
		assertRelevanceRanked(t, &TaskCollection{ProjectID: 1, ProjectViewID: 1})
	})

	// An explicit sort_by must win over relevance: with `id desc` the lowest-id
	// task (allWords) ranks last, the opposite of what BM25 relevance would do.
	// This locks the contract that user-provided sorting disables relevance
	// ranking even on ParadeDB. Only ParadeDB's per-token search matches all
	// three tasks, so the ordering contract is only asserted there (other
	// databases ILIKE the whole phrase and match a different subset).
	t.Run("explicit sort disables relevance ranking", func(t *testing.T) {
		if !db.ParadeDBAvailable() {
			t.Skip("relevance ranking only applies on ParadeDB")
		}

		tc := &TaskCollection{
			ProjectID: 1,
			SortBy:    []string{"id"},
			OrderBy:   []string{"desc"},
		}
		got, _, _, err := tc.ReadAll(s, usr, "backup server", 0, 50)
		require.NoError(t, err)

		gotTasks, is := got.([]*Task)
		require.True(t, is)

		created := map[int64]bool{allWords.ID: true, oneWordA.ID: true, oneWordB.ID: true}
		var orderedIDs []int64
		for _, tsk := range gotTasks {
			if created[tsk.ID] {
				orderedIDs = append(orderedIDs, tsk.ID)
			}
		}

		require.Len(t, orderedIDs, len(created), "all created tasks should match the search")
		for i := 1; i < len(orderedIDs); i++ {
			assert.Greater(t, orderedIDs[i-1], orderedIDs[i], "tasks must follow the explicit id-desc sort, not relevance")
		}
		assert.Equal(t, allWords.ID, orderedIDs[len(orderedIDs)-1], "the all-words match (lowest id) ranks last under id-desc, proving relevance was not applied")
	})
}