package voice

import (
	"context"
	"fmt"

	"git.yeij.top/AskaEth/Cyrene_v2/internal/config"
)

// Chain is a degrading provider list. STT and TTS walk the steps in order,
// returning the first successful result and moving to the next step when a
// provider is unavailable (nil direction) or fails. It implements STT and TTS so
// it can be used anywhere a single provider is expected.
type Chain struct {
	steps []Provider
}

// NewChain builds a degrading chain from the given providers in the order they
// should be tried. Passing a SilentProvider last guarantees the chain always
// succeeds.
func NewChain(steps ...Provider) *Chain {
	return &Chain{steps: steps}
}

// STT walks the chain for a transcription.
func (c *Chain) STT(ctx context.Context, audio Audio) (string, error) {
	if len(c.steps) == 0 {
		return "", ErrProviderFailed
	}
	var lastErr error
	for _, p := range c.steps {
		stt := p.STT()
		if stt == nil {
			continue
		}
		text, err := stt.STT(ctx, audio)
		if err == nil {
			return text, nil
		}
		lastErr = err
	}
	return "", fmt.Errorf("voice: %w: %v", ErrProviderFailed, lastErr)
}

// TTS walks the chain for synthesized audio.
func (c *Chain) TTS(ctx context.Context, text string) (Audio, error) {
	if len(c.steps) == 0 {
		return Audio{}, ErrProviderFailed
	}
	var lastErr error
	for _, p := range c.steps {
		tts := p.TTS()
		if tts == nil {
			continue
		}
		audio, err := tts.TTS(ctx, text)
		if err == nil {
			return audio, nil
		}
		lastErr = err
	}
	return Audio{}, fmt.Errorf("voice: %w: %v", ErrProviderFailed, lastErr)
}

// Option customizes a chain built by New.
type Option func(*chainConfig)

// chainConfig carries the assembled steps for New.
type chainConfig struct {
	steps []Provider
}

// WithProviders overrides the provider steps assembled from config. Tests use it
// to inject deterministic mock providers instead of the real adaptation-point
// rungs.
func WithProviders(steps ...Provider) Option {
	return func(c *chainConfig) { c.steps = steps }
}

// New assembles a chain from cfg using the fixed degradation order
// cloud → local → edge-tts/espeak → silent.
//
//   - cloud is included only when a cloud voice setting is present (today an
//     API key) so a mis-configured build degrades quietly.
//   - local is a pure adaptation point and is only included when supplied via
//     WithProviders; by default it is skipped.
//   - the edge-tts or espeak rung is included according to cfg.TTSProvider.
//   - silent is always appended last so the chain never fails outright.
//
// opts may supply a fully assembled step list to override this mapping.
func New(cfg config.VoiceConfig, opts ...Option) *Chain {
	conf := &chainConfig{}
	for _, o := range opts {
		o(conf)
	}
	if len(conf.steps) > 0 {
		return NewChain(conf.steps...)
	}

	steps := make([]Provider, 0, 5)
	if cfg.DashscopeAPIKey != "" {
		steps = append(steps, CloudProvider(newDashboardSTT(cfg), newDashboardTTS(cfg)))
	}
	switch cfg.TTSProvider {
	case "edge-tts", "edge":
		steps = append(steps, EdgeTTSProvider(newEdgeTTS()))
	case "espeak":
		steps = append(steps, EspeakProvider(newEspeak()))
	}
	steps = append(steps, SilentProvider())
	return NewChain(steps...)
}