package classes

import (
	"context"
	"fmt"
	"strings"

	"git.golem15.com/golem15/sm-seo-plugin/models"
	"git.golem15.com/golem15/summercms/modules/conga"
	"git.golem15.com/golem15/summercms/modules/lagoon"
	"git.golem15.com/golem15/summercms/modules/pact"
	"gorm.io/gorm"
)

// GenerateKind is the River kind of the entry generation job.
const GenerateKind = "golem15.seo.generate_entries"

// generatePage is the page size of the generation job.
const generatePage = 200

// GenerateEntriesArgs are the arguments of the entry generation job (D-94,
// the mpseo GenerateSeoEntriesJob): Type limits it to one content type
// key; empty runs every content type.
type GenerateEntriesArgs struct {
	Type string `json:"type"`
}

// Kind is GenerateKind.
func (GenerateEntriesArgs) Kind() string { return GenerateKind }

// GenerateResult counts what one generation run did.
type GenerateResult struct {
	Created int
	Updated int
}

// GenerateEntries walks the published records of every content type (or
// of typeKey) through their descriptors and makes sure each locale with an
// address has an entry: a missing one is created with the URL, an existing
// one gets its URL, type and effective title and description cache
// refreshed. Editor values are never written. Each page of records is one
// transaction.
func (s *Service) GenerateEntries(ctx context.Context, typeKey string) (GenerateResult, error) {
	var res GenerateResult
	reg := s.Registry()
	if reg == nil {
		return res, nil
	}
	db, err := s.DB(ctx)
	if err != nil {
		return res, err
	}
	var types []pact.MenuItemType
	for _, typ := range reg.ContentTypes() {
		if typeKey == "" || typ.Key == typeKey {
			types = append(types, typ)
		}
	}
	if typeKey != "" && len(types) == 0 {
		return res, fmt.Errorf("golem15.seo: content type %q is not registered", typeKey)
	}
	settings, err := LoadSettings(db)
	if err != nil {
		return res, err
	}
	for _, typ := range types {
		ts, err := LoadTypeSetting(db, typ.Key)
		if err != nil {
			return res, err
		}
		after := ""
		for {
			page, err := reg.Records(ctx, typ.Key, after, generatePage, s.UnprefixedLocale())
			if err != nil {
				return res, err
			}
			if err := db.Transaction(func(tx *gorm.DB) error {
				for _, rec := range page.Records {
					if !rec.Published {
						continue
					}
					for _, l := range rec.Locales {
						if strings.TrimSpace(l.URL) == "" {
							continue
						}
						created, err := s.refreshEntry(ctx, tx, typ, rec.ID, l, settings, ts)
						if err != nil {
							return err
						}
						if created {
							res.Created++
						} else {
							res.Updated++
						}
					}
				}
				return nil
			}); err != nil {
				return res, err
			}
			if page.Next == "" || page.Next == after || len(page.Records) == 0 {
				break
			}
			after = page.Next
		}
	}
	return res, nil
}

// refreshEntry creates or refreshes the entry of one record in one
// locale; created is true for a new row. The job only sees published
// records, so an entry whose URL differs from the record's address gets
// the address change (with its 301), never a silent overwrite.
func (s *Service) refreshEntry(ctx context.Context, tx *gorm.DB, typ pact.MenuItemType, id string, l pact.ContentLocale, settings models.Settings, ts models.TypeSetting) (bool, error) {
	entry, found, err := LoadEntry(tx, typ.Content.Model, id, l.Locale)
	if err != nil {
		return false, err
	}
	site := s.translatedSetting(ctx, tx, &settings, "site_name", settings.SiteName, l.Locale)
	fallback := s.translatedSetting(ctx, tx, &settings, "default_description", settings.DefaultDescription, l.Locale)
	title, description := EffectiveValues(entry, l, settings, ts, site, fallback)
	if !found {
		row := models.Entry{
			ModelType: typ.Content.Model, RecordID: id, Locale: l.Locale, TypeKey: typ.Key, URL: l.URL,
			EffectiveTitle: title, EffectiveDescription: description,
		}
		return true, tx.Create(&row).Error
	}
	updates := map[string]any{
		"type_key":              typ.Key,
		"effective_title":       title,
		"effective_description": description,
	}
	switch {
	case entry.URL == "":
		updates["url"] = l.URL
	case entry.URL != l.URL:
		// The published record's address changed and no RecordSaved
		// listener has seen it yet (WR-19): apply it like the listener
		// would, so its 301 is not lost; AddressChanged moves the entry's
		// URL.
		if _, err := s.AddressChanged(ctx, tx, AddressChange{
			TypeKey: typ.Key, ModelType: typ.Content.Model, RecordID: id, Locale: l.Locale,
			Old: entry.URL, New: l.URL,
		}); err != nil {
			return false, err
		}
	}
	return false, tx.Model(&models.Entry{}).Where("id = ?", entry.ID).Updates(updates).Error
}

// EffectiveValues are a record's effective title and description without
// URL rules (the cache duplicate checks read): the record's values, else
// the type or general template on the content, else the content's own,
// else the settings.
func EffectiveValues(entry models.Entry, l pact.ContentLocale, settings models.Settings, ts models.TypeSetting, site, fallback string) (string, string) {
	vars := TemplateVars{Title: l.Title, Description: l.Description, Site: site}
	tpl := ts.TitleTemplate
	if strings.TrimSpace(tpl) == "" {
		tpl = settings.TitleTemplate
	}
	title, _ := pick(candidate{entry.Title, SourceRecord}, candidate{RenderTemplate(tpl, vars), SourceTemplate}, candidate{l.Title, SourceContent}, candidate{site, SourceGlobal})
	description, _ := pick(candidate{entry.Description, SourceRecord}, candidate{RenderTemplate(ts.DescriptionTemplate, vars), SourceTemplate}, candidate{l.Description, SourceContent}, candidate{fallback, SourceGlobal})
	return title, description
}

// EnqueueGenerate queues the generation job through conga for typeKey
// (empty: every type) and returns the summer_jobs id.
func (s *Service) EnqueueGenerate(ctx context.Context, db *gorm.DB, typeKey string) (uint, error) {
	if s == nil || s.app == nil {
		return 0, ErrNotBooted
	}
	m, err := conga.From(s.app)
	if err != nil {
		return 0, err
	}
	return m.Dispatch(ctx, db, GenerateEntriesArgs{Type: typeKey}, conga.DispatchOpts{Label: s.Phrase("golem15.seo::lang.jobs.generate_entries", nil)})
}

// RecordDeleted removes the entries of a deleted record in one
// transaction and records each in history (via auto), so its values stay
// recoverable (D-92, D-94). A model without a content type is ignored.
func (s *Service) RecordDeleted(ctx context.Context, ev *pact.RecordDeleted) error {
	reg := s.Registry()
	if reg == nil || ev == nil {
		return nil
	}
	typ, ok := reg.ContentTypeForModel(ev.Model)
	if !ok || typ.Content == nil {
		return nil
	}
	db, err := s.DB(ctx)
	if err != nil {
		return err
	}
	ctx = WithVia(ctx, models.ViaAuto)
	// A lagoon transaction, so the history it records purges the site
	// cache after the commit.
	return lagoon.Transaction(ctx, db, func(ctx context.Context, tx *gorm.DB) error {
		entries, err := LoadEntries(tx, typ.Content.Model, ev.ID)
		if err != nil || len(entries) == 0 {
			return err
		}
		if err := tx.Where("model_type = ? AND record_id = ?", typ.Content.Model, ev.ID).Delete(&models.Entry{}).Error; err != nil {
			return err
		}
		for locale, e := range entries {
			if entryEmpty(e) {
				continue
			}
			title := e.EffectiveTitle
			if title == "" {
				title = e.URL
			}
			if err := s.Record(ctx, tx, Change{
				Kind:      models.SubjectEntry,
				SubjectID: EntrySubject(e.ModelType, e.RecordID, locale),
				What:      s.recordWhat(typ, ev.ID, pact.ContentLocale{Title: title}, locale),
				Before:    entryValues(e),
			}); err != nil {
				return err
			}
		}
		return nil
	})
}

// RecordCreated stores the address snapshot of a newly created record:
// each locale with an address gets an entry with its URL (existing entries,
// written by the SEO tab in the same save, only take the URL).
func (s *Service) RecordCreated(ctx context.Context, ev *pact.RecordSaved) error {
	reg := s.Registry()
	if reg == nil || ev == nil || !ev.Created {
		return nil
	}
	typ, ok := reg.ContentTypeForModel(ev.Model)
	if !ok || typ.Content == nil {
		return nil
	}
	rec, err := reg.Describe(ctx, typ.Key, ev.ID, s.UnprefixedLocale())
	if err != nil || rec == nil {
		return err
	}
	db, err := s.DB(ctx)
	if err != nil {
		return err
	}
	return db.Transaction(func(tx *gorm.DB) error {
		for _, l := range rec.Locales {
			if strings.TrimSpace(l.URL) == "" {
				continue
			}
			entry, found, err := LoadEntry(tx, typ.Content.Model, ev.ID, l.Locale)
			if err != nil {
				return err
			}
			if found {
				if err := tx.Model(&models.Entry{}).Where("id = ?", entry.ID).Updates(map[string]any{"url": l.URL, "type_key": typ.Key}).Error; err != nil {
					return err
				}
				continue
			}
			row := models.Entry{ModelType: typ.Content.Model, RecordID: ev.ID, Locale: l.Locale, TypeKey: typ.Key, URL: l.URL}
			if err := tx.Create(&row).Error; err != nil {
				return err
			}
		}
		return nil
	})
}