package library

import (
	"context"
	"errors"
	"fmt"
	"sync"
	"time"

	"github.com/jackc/pgx/v5/pgxpool"

	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
)

// AcoustID lookup settings (M401 #3922). Rule 25: a database row, changed
// without a restart, shared by the worker and the admin API.

// AcoustIDSettings mirrors the acoustid_settings row.
type AcoustIDSettings struct {
	Enabled bool
	// APIKey is the operator's registered application key. Never sent back
	// to the browser; the API reports only whether one is set.
	APIKey string
	// MinScore is the AcoustID score a recording needs to be considered.
	MinScore float32
	// UpdatedAt is set by the database.
	UpdatedAt time.Time
}

// Ready reports whether the worker may call AcoustID at all.
func (s AcoustIDSettings) Ready() bool { return s.Enabled && s.APIKey != "" }

// DefaultAcoustIDSettings mirrors migration 0069's defaults: off, no key.
var DefaultAcoustIDSettings = AcoustIDSettings{MinScore: 0.85}

// The score threshold's bounds, as migration 0069's CHECK has them. Below 0.5
// AcoustID's own docs call a match doubtful; the floor keeps a typo in the
// field from filling the library with guesses.
const (
	minAcoustIDScore = 0.5
	maxAcoustIDScore = 1
)

// ErrAcoustIDSettingOutOfRange is returned by Set for a value the CHECK would
// reject, so the API answers 400 naming the field.
var ErrAcoustIDSettingOutOfRange = errors.New("acoustid setting out of range")

// AcoustIDSettingsUpdate is the admin save. A nil APIKey keeps the stored key;
// an empty one clears it.
type AcoustIDSettingsUpdate struct {
	Enabled  bool
	MinScore float32
	APIKey   *string
}

// AcoustIDSettingsService caches the settings and owns their persistence.
type AcoustIDSettingsService struct {
	pool *pgxpool.Pool

	mu  sync.RWMutex
	cur AcoustIDSettings
	// changed is signalled after every save, so the worker can start a pass
	// at once instead of waiting out its tick.
	changed chan struct{}
}

// NewAcoustIDSettingsService loads once and caches. It always returns a usable
// service, holding the defaults (off) when the load fails; the error says so.
func NewAcoustIDSettingsService(ctx context.Context, pool *pgxpool.Pool) (*AcoustIDSettingsService, error) {
	s := &AcoustIDSettingsService{pool: pool, cur: DefaultAcoustIDSettings, changed: make(chan struct{}, 1)}
	row, err := dbq.New(pool).GetAcoustIDSettings(ctx)
	if err != nil {
		return s, fmt.Errorf("acoustid settings: load: %w", err)
	}
	s.cur = acoustIDSettingsFromRow(row)
	return s, nil
}

// Get returns the cached settings. A nil service answers with the defaults.
func (s *AcoustIDSettingsService) Get() AcoustIDSettings {
	if s == nil {
		return DefaultAcoustIDSettings
	}
	s.mu.RLock()
	defer s.mu.RUnlock()
	return s.cur
}

// Set validates, persists and re-caches.
func (s *AcoustIDSettingsService) Set(ctx context.Context, in AcoustIDSettingsUpdate) (AcoustIDSettings, error) {
	if in.MinScore < minAcoustIDScore || in.MinScore > maxAcoustIDScore {
		return AcoustIDSettings{}, fmt.Errorf("%w: min_score must be %.2f-%.2f",
			ErrAcoustIDSettingOutOfRange, float32(minAcoustIDScore), float32(maxAcoustIDScore))
	}
	if s == nil {
		return AcoustIDSettings{}, errors.New("acoustid settings: no settings service")
	}
	params := dbq.UpdateAcoustIDSettingsParams{Enabled: in.Enabled, MinScore: in.MinScore}
	if in.APIKey != nil {
		params.SetApiKey = true
		params.ApiKey = *in.APIKey
	}
	row, err := dbq.New(s.pool).UpdateAcoustIDSettings(ctx, params)
	if err != nil {
		return AcoustIDSettings{}, fmt.Errorf("acoustid settings: save: %w", err)
	}
	out := acoustIDSettingsFromRow(row)
	s.mu.Lock()
	s.cur = out
	s.mu.Unlock()
	select {
	case s.changed <- struct{}{}:
	default:
	}
	return out, nil
}

// Changed is signalled after a save. A nil service never signals.
func (s *AcoustIDSettingsService) Changed() <-chan struct{} {
	if s == nil {
		return nil
	}
	return s.changed
}

func acoustIDSettingsFromRow(row dbq.AcoustidSetting) AcoustIDSettings {
	out := AcoustIDSettings{Enabled: row.Enabled, MinScore: row.MinScore, UpdatedAt: row.UpdatedAt.Time}
	if row.ApiKey != nil {
		out.APIKey = *row.ApiKey
	}
	return out
}