package classes

import (
	"context"
	"fmt"
	"strings"
	"time"

	"git.golem15.com/golem15/sm-sitemap-plugin/models"
	"git.golem15.com/golem15/summercms/modules/backpack"
	"git.golem15.com/golem15/summercms/modules/compass"
	"git.golem15.com/golem15/summercms/modules/conga"
	"git.golem15.com/golem15/summercms/modules/pact"
	"git.golem15.com/golem15/summercms/modules/signpost"
	"gorm.io/gorm"
)

// The config keys of the event-driven lastmod and the debounced rebuild.
const (
	// LastmodIgnoreConfigKey lists the attributes whose change does not
	// move lastmod.
	LastmodIgnoreConfigKey = "golem15.sitemap.lastmod_ignore"
	// RebuildDelayConfigKey is the delay of the rebuild a record event
	// queues, in seconds.
	RebuildDelayConfigKey = "golem15.sitemap.rebuild_delay_seconds"
)

// DefaultLastmodIgnore is the ignore list when the config has none.
var DefaultLastmodIgnore = []string{"updated_at", "created_at", "views", "sort_order"}

// defaultRebuildDelay is the rebuild delay when the config has none.
const defaultRebuildDelay = 60 * time.Second

// LastmodIgnore reads golem15.sitemap.lastmod_ignore: a list of attribute
// names (or one comma-separated string); DefaultLastmodIgnore when unset.
func LastmodIgnore(cfg *compass.Config) map[string]bool {
	names := DefaultLastmodIgnore
	if cfg != nil {
		if v, ok := cfg.Lookup(LastmodIgnoreConfigKey); ok && v != nil {
			names = nil
			switch list := v.(type) {
			case []any:
				for _, item := range list {
					names = append(names, fmt.Sprint(item))
				}
			case []string:
				names = list
			case string:
				names = strings.Split(list, ",")
			}
		}
	}
	out := make(map[string]bool, len(names))
	for _, n := range names {
		if n = strings.TrimSpace(n); n != "" {
			out[n] = true
		}
	}
	return out
}

// RebuildDelay reads golem15.sitemap.rebuild_delay_seconds; 60 seconds when
// unset, 0 or more when set.
func RebuildDelay(cfg *compass.Config) time.Duration {
	if cfg == nil || !cfg.Has(RebuildDelayConfigKey) {
		return defaultRebuildDelay
	}
	if n := cfg.Int(RebuildDelayConfigKey); n > 0 {
		return time.Duration(n) * time.Second
	}
	return 0
}

// Changed is what a save changed for lastmod: Any when a change outside the
// ignore list exists, All when one of them is on the record's own row
// (every locale's address moves), else Locales names the translated
// locales that changed.
type Changed struct {
	Any     bool
	All     bool
	Locales map[string]bool
}

// RealChanges filters a save's changes through the ignore list. A no-op
// save (no changes) and one that changes only ignored attributes change
// nothing (RESEARCH Pitfall 4).
func RealChanges(changes []pact.RecordChange, ignore map[string]bool) Changed {
	out := Changed{Locales: map[string]bool{}}
	for _, c := range changes {
		if ignore[c.Attribute] {
			continue
		}
		out.Any = true
		if c.Locale == "" {
			out.All = true
			continue
		}
		out.Locales[c.Locale] = true
	}
	if out.All {
		out.Locales = map[string]bool{}
	}
	return out
}

// RecordSaved handles a saved record of a content type (D-30): when the
// save changed an attribute outside golem15.sitemap.lastmod_ignore, the
// lastmod of the record's rows moves to now (every locale's for a change
// on the record's own row, else only the changed locales'), and a
// debounced rebuild is queued. A model no content type declares is
// ignored.
func RecordSaved(ctx context.Context, app *backpack.App, ev *pact.RecordSaved) error {
	typ, db, ok := contentTypeOf(app, ev.Model)
	if !ok || ev == nil {
		return nil
	}
	changed := RealChanges(ev.Changes, LastmodIgnore(app.Config))
	if !changed.Any {
		return nil
	}
	db = db.WithContext(ctx)
	now := time.Now().UTC().Truncate(time.Microsecond)
	q := db.Model(&models.URL{}).Where("type_key = ? AND record_id = ?", typ, ev.ID)
	if !changed.All {
		locales := make([]string, 0, len(changed.Locales))
		for l := range changed.Locales {
			locales = append(locales, l)
		}
		q = q.Where("locale IN ?", locales)
	}
	if err := q.Updates(map[string]any{"lastmod": now, "updated_at": now}).Error; err != nil {
		return err
	}
	return RequestDebouncedRebuild(ctx, app, db)
}

// RecordDeleted handles a deleted record of a content type: its rows leave
// the files at once (reason deleted, their file numbers kept as holes) and
// a debounced rebuild is queued.
func RecordDeleted(ctx context.Context, app *backpack.App, ev *pact.RecordDeleted) error {
	if ev == nil {
		return nil
	}
	typ, db, ok := contentTypeOf(app, ev.Model)
	if !ok {
		return nil
	}
	db = db.WithContext(ctx)
	now := time.Now().UTC()
	if err := db.Model(&models.URL{}).
		Where("type_key = ? AND record_id = ? AND excluded_reason <> ?", typ, ev.ID, models.ReasonDeleted).
		Updates(map[string]any{"excluded_reason": models.ReasonDeleted, "updated_at": now}).Error; err != nil {
		return err
	}
	return RequestDebouncedRebuild(ctx, app, db)
}

// contentTypeOf finds the content type key of a record event's model and
// the application database.
func contentTypeOf(app *backpack.App, model string) (string, *gorm.DB, bool) {
	if app == nil {
		return "", nil, false
	}
	reg, ok := app.Lookup[*signpost.Registry]()
	if !ok || reg == nil {
		return "", nil, false
	}
	typ, ok := reg.ContentTypeForModel(model)
	if !ok || typ.Content == nil {
		return "", nil, false
	}
	db, ok := app.Lookup[*gorm.DB]()
	if !ok || db == nil {
		return "", nil, false
	}
	return typ.Key, db, true
}

// RequestDebouncedRebuild queues one rebuild golem15.sitemap.rebuild_delay_seconds
// from now unless one is already pending (P33-12): a conditional UPDATE of
// rebuild_pending_until decides, and the job is enqueued in the same
// transaction, so events within the delay share one rebuild. The job
// clears the pending time when it starts.
func RequestDebouncedRebuild(ctx context.Context, app *backpack.App, db *gorm.DB) error {
	delay := RebuildDelay(app.Config)
	m, err := conga.From(app)
	if err != nil {
		return err
	}
	return db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		res := tx.Exec(`UPDATE golem15_sitemap_settings
SET rebuild_pending_until = NOW() + make_interval(secs => ?)
WHERE id = 1 AND (rebuild_pending_until IS NULL OR rebuild_pending_until <= NOW())`, delay.Seconds())
		if res.Error != nil || res.RowsAffected == 0 {
			return res.Error
		}
		return m.Enqueue(ctx, tx, RebuildArgs{}, conga.EnqueueOpts{Delay: delay})
	})
}

// ClearPending ends the debounce window; the rebuild job calls it when it
// starts, so events during the rebuild queue the next one.
func ClearPending(ctx context.Context, app *backpack.App) error {
	db, ok := app.Lookup[*gorm.DB]()
	if !ok || db == nil {
		return ErrNoDatabase
	}
	return db.WithContext(ctx).Exec(`UPDATE golem15_sitemap_settings SET rebuild_pending_until = NULL WHERE id = 1`).Error
}