package test

import (
	"RenewCMS/internal/domain/article"
	"RenewCMS/internal/infrastructure/persistence/database"
	entity "RenewCMS/internal/infrastructure/persistence/models"
	"errors"
	"fmt"
	"testing"
	"time"

	"gorm.io/gorm"
)

const (
	backfillArticleCount = 5000
	backfillIndexName    = "idx_articles_site_slug"
)

type backfillWrites struct {
	updates      int
	rows         int64
	transactions map[any]bool
	failFrom     int
}

func watchBackfillWrites(t *testing.T, db *gorm.DB) *backfillWrites {
	t.Helper()
	writes := &backfillWrites{transactions: map[any]bool{}}
	name := fmt.Sprintf("backfill-writes-%s", t.Name())
	err := db.Callback().Update().Before("gorm:update").Register(name, func(tx *gorm.DB) {
		if tx.Statement.Table != "articles" {
			return
		}
		if writes.failFrom > 0 && writes.updates+1 >= writes.failFrom {
			_ = tx.AddError(errors.New("injected failure"))
			return
		}
		writes.updates++
		writes.transactions[tx.Statement.ConnPool] = true
	})
	if err != nil {
		t.Fatalf("register callback: %v", err)
	}
	err = db.Callback().Update().After("gorm:update").Register(name+"-rows", func(tx *gorm.DB) {
		if tx.Statement.Table == "articles" {
			writes.rows += tx.RowsAffected
		}
	})
	if err != nil {
		t.Fatalf("register callback: %v", err)
	}
	t.Cleanup(func() {
		_ = db.Callback().Update().Remove(name)
		_ = db.Callback().Update().Remove(name + "-rows")
	})
	return writes
}

func openLegacyArticleDatabase(t *testing.T) *gorm.DB {
	t.Helper()
	db := openUnmigratedSQLite(t)
	if err := database.Migrate(db, migrationPublicURL); err != nil {
		t.Fatalf("migrate: %v", err)
	}
	if err := db.Exec("DROP INDEX " + backfillIndexName).Error; err != nil {
		t.Fatalf("drop index: %v", err)
	}
	return db
}

func seedLegacyArticles(t *testing.T, db *gorm.DB, rows []entity.Article) {
	t.Helper()
	if err := db.CreateInBatches(&rows, 100).Error; err != nil {
		t.Fatalf("seed: %v", err)
	}
}

func legacyArticles(count int) []entity.Article {
	rows := make([]entity.Article, 0, count)
	for i := 1; i <= count; i++ {
		rows = append(rows, entity.Article{Title: fmt.Sprintf("Legacy %04d", i), SiteID: uint32(i%2 + 1)})
	}
	return rows
}

type backfillRow struct {
	Slug      string
	UpdatedAt time.Time
}

func storedBackfillRows(t *testing.T, db *gorm.DB) map[uint32]backfillRow {
	t.Helper()
	var rows []entity.Article
	if err := db.Unscoped().Find(&rows).Error; err != nil {
		t.Fatalf("read: %v", err)
	}
	found := make(map[uint32]backfillRow, len(rows))
	for _, row := range rows {
		found[row.ID] = backfillRow{Slug: row.Slug, UpdatedAt: row.UpdatedAt}
	}
	return found
}

func countBackfillIndex(t *testing.T, db *gorm.DB) int64 {
	t.Helper()
	var count int64
	if err := db.Raw("SELECT COUNT(*) FROM sqlite_master WHERE type = 'index' AND name = ?", backfillIndexName).Scan(&count).Error; err != nil {
		t.Fatalf("index lookup: %v", err)
	}
	return count
}

func TestBackfillArticleSlugs(t *testing.T) {
	t.Run("A large database is filled in batches", func(t *testing.T) {
		db := openLegacyArticleDatabase(t)
		seedLegacyArticles(t, db, legacyArticles(backfillArticleCount))
		writes := watchBackfillWrites(t, db)

		if err := database.BackfillArticleSlugs(db); err != nil {
			t.Fatalf("backfill: %v", err)
		}

		seen := map[string]bool{}
		for id, row := range storedBackfillRows(t, db) {
			var siteID uint32
			if err := db.Unscoped().Model(&entity.Article{}).Where("id = ?", id).Select("site_id").Scan(&siteID).Error; err != nil {
				t.Fatalf("site: %v", err)
			}
			key := fmt.Sprintf("%d/%s", siteID, row.Slug)
			if row.Slug == "" || seen[key] {
				t.Fatalf("article %d has an empty or duplicate slug %q", id, row.Slug)
			}
			seen[key] = true
		}
		if writes.updates != backfillArticleCount || len(writes.transactions) < 2 || len(writes.transactions) > backfillArticleCount/100 {
			t.Errorf("updates %d in %d transactions", writes.updates, len(writes.transactions))
		}
	})

	t.Run("The second boot changes nothing", func(t *testing.T) {
		db := openLegacyArticleDatabase(t)
		seedLegacyArticles(t, db, legacyArticles(300))
		if err := database.BackfillArticleSlugs(db); err != nil {
			t.Fatalf("backfill: %v", err)
		}
		before := storedBackfillRows(t, db)
		writes := watchBackfillWrites(t, db)

		for i := 0; i < 2; i++ {
			if err := database.Migrate(db, migrationPublicURL); err != nil {
				t.Fatalf("migrate: %v", err)
			}
		}

		after := storedBackfillRows(t, db)
		for id, row := range before {
			if after[id] != row {
				t.Fatalf("article %d changed from %+v to %+v", id, row, after[id])
			}
		}
		if writes.rows != 0 {
			t.Errorf("second boot wrote %d rows", writes.rows)
		}
		if countBackfillIndex(t, db) != 1 {
			t.Errorf("%s must exist exactly once", backfillIndexName)
		}
	})

	t.Run("A crashed backfill resumes", func(t *testing.T) {
		db := openLegacyArticleDatabase(t)
		seedLegacyArticles(t, db, legacyArticles(1200))
		writes := watchBackfillWrites(t, db)
		writes.failFrom = 501

		if err := database.BackfillArticleSlugs(db); err == nil {
			t.Fatalf("expected the injected failure")
		}
		interrupted := storedBackfillRows(t, db)
		filled := map[uint32]string{}
		for id, row := range interrupted {
			if row.Slug != "" {
				filled[id] = row.Slug
			}
		}
		if len(filled) == 0 || len(filled) >= 1200 {
			t.Fatalf("expected a partial run, %d filled", len(filled))
		}

		writes.failFrom = 0
		if err := database.BackfillArticleSlugs(db); err != nil {
			t.Fatalf("resume: %v", err)
		}
		for id, row := range storedBackfillRows(t, db) {
			if row.Slug == "" {
				t.Fatalf("article %d still empty", id)
			}
			if slug, wasFilled := filled[id]; wasFilled && slug != row.Slug {
				t.Fatalf("article %d changed from %q to %q", id, slug, row.Slug)
			}
		}
	})

	t.Run("Duplicates get the first free suffix", func(t *testing.T) {
		db := openLegacyArticleDatabase(t)
		seedLegacyArticles(t, db, []entity.Article{
			{Title: "Same Title", SiteID: 1}, {Title: "Same Title", SiteID: 1}, {Title: "Same Title", SiteID: 1}, {Title: "Same Title", SiteID: 2},
		})
		if err := database.BackfillArticleSlugs(db); err != nil {
			t.Fatalf("backfill: %v", err)
		}
		rows := storedBackfillRows(t, db)
		if rows[1].Slug != "same-title" || rows[2].Slug != "same-title-2" || rows[3].Slug != "same-title-3" || rows[4].Slug != "same-title" {
			t.Errorf("slugs = %+v", rows)
		}
	})

	t.Run("Soft-deleted rows get their tombstone once and existing slugs are kept", func(t *testing.T) {
		db := openLegacyArticleDatabase(t)
		seedLegacyArticles(t, db, []entity.Article{{Title: "Gone one", SiteID: 1}, {Title: "Gone two", SiteID: 1}, {Title: "Owner set", Slug: "chosen-by-owner", SiteID: 1}})
		if err := db.Where("id IN ?", []uint32{1, 2}).Delete(&entity.Article{}).Error; err != nil {
			t.Fatalf("soft delete: %v", err)
		}
		if err := database.BackfillArticleSlugs(db); err != nil {
			t.Fatalf("backfill: %v", err)
		}
		first := storedBackfillRows(t, db)
		if first[1].Slug != article.Tombstone(1) || first[2].Slug != article.Tombstone(2) || first[3].Slug != "chosen-by-owner" {
			t.Fatalf("slugs = %+v", first)
		}
		writes := watchBackfillWrites(t, db)
		if err := database.BackfillArticleSlugs(db); err != nil {
			t.Fatalf("second run: %v", err)
		}
		if writes.updates != 0 || writes.rows != 0 {
			t.Errorf("second run wrote %d rows", writes.rows)
		}
	})
}