package coverart

import (
	"context"
	"errors"
	"sync/atomic"
)

// mbcaaProvider implements Provider, AlbumCoverProvider, and
// TestableProvider. It wraps an *Fetcher (the existing
// MBCAA-specific HTTP client) for the actual fetch logic, adapting
// the Fetcher's Fetch method to the AlbumCoverProvider interface.
//
// The wrapping (rather than reimplementing) is temporary: A-T8 will
// consolidate fetcher.go's logic into this file and delete fetcher.go.
// During the T4–T8 window, this struct lets the new provider chain
// coexist with the legacy Fetcher used by enricher.go and main.go.
type mbcaaProvider struct {
	fetcher *Fetcher
	enabled atomic.Bool
}

// Sample MBID used by TestConnection. The Beatles' "Abbey Road" UK
// release; verified present on MBCAA at design time. Both 200 (image
// returned) and 404 (no art for the sample) are treated as "connection
// works" since MBCAA needs no auth — only network failures surface.
const mbcaaTestSampleMBID = "f4b3df80-8a6c-3e87-b51e-5c1ee70a78ee"

func init() {
	// Register with a default-config Fetcher. main.go (in A-T8) will
	// call NewMBCAAProviderFromConfig to swap in the production
	// User-Agent + MinPeriod. Default config values come from
	// FetcherConfig's zero-value handling in NewFetcher.
	Register(&mbcaaProvider{
		fetcher: NewFetcher(FetcherConfig{}),
	})
}

// NewMBCAAProviderFromConfig replaces the registered MBCAA provider's
// internal Fetcher with one built from the supplied config. main.go
// calls this at boot to set the production User-Agent. Idempotent;
// safe to call repeatedly.
func NewMBCAAProviderFromConfig(cfg FetcherConfig) {
	p, err := ProviderByID("mbcaa")
	if err != nil {
		// init() should have registered it; if not, register fresh.
		Register(&mbcaaProvider{fetcher: NewFetcher(cfg)})
		return
	}
	mp, ok := p.(*mbcaaProvider)
	if !ok {
		// Some other provider claimed the "mbcaa" ID — registry bug.
		panic("coverart: provider with ID 'mbcaa' is not *mbcaaProvider")
	}
	mp.fetcher = NewFetcher(cfg)
}

func (p *mbcaaProvider) ID() string           { return "mbcaa" }
func (p *mbcaaProvider) DisplayName() string  { return "Cover Art Archive" }
func (p *mbcaaProvider) RequiresAPIKey() bool { return false }
func (p *mbcaaProvider) DefaultEnabled() bool { return true }

func (p *mbcaaProvider) Configure(s ProviderSettings) error {
	p.enabled.Store(s.Enabled)
	return nil // MBCAA has no per-operator config beyond enabled
}

// FetchAlbumCover delegates to the wrapped Fetcher. The Fetcher's
// existing Fetch method already returns ErrNotFound / ErrTransient
// per the contract, so no error mapping is needed.
func (p *mbcaaProvider) FetchAlbumCover(ctx context.Context, mbid string) ([]byte, error) {
	if !p.enabled.Load() {
		return nil, ErrNotFound // defensive; enricher already filters on enabled
	}
	return p.fetcher.Fetch(ctx, mbid)
}

// TestConnection hits the sample MBID's front-500 endpoint. A 200
// (image bytes) or 404 (no art for sample) both indicate the
// connection works; 5xx / network errors surface as TestConnection
// failures.
func (p *mbcaaProvider) TestConnection(ctx context.Context) error {
	_, err := p.fetcher.Fetch(ctx, mbcaaTestSampleMBID)
	if err == nil {
		return nil
	}
	if errors.Is(err, ErrNotFound) {
		return nil
	}
	return err
}