package voice

import (
	"bytes"
	"context"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"io"
	"log/slog"
	"net/http"
	"strings"
	"time"

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

// cloudMaxResponseBytes caps how much of a cloud voice response is read, so an
// oversized or malformed response cannot exhaust memory. The request timeout
// bounds a single call.
const (
	cloudMaxResponseBytes = 8 << 20
	cloudHTTPTimeout      = 180 * time.Second
)

// HTTPSTT transcribes audio by POSTing a JSON body to a cloud endpoint and
// reading {"text": "..."} back. It is the stubbed default STT implementation;
// the real DashScope/whisper-facing adapter is an adaptation point.
type HTTPSTT struct {
	endpoint string
	apiKey   string
	client   *http.Client
	log      *slog.Logger
}

// HTTPTTS synthesizes speech by POSTing a JSON body and reading the returned
// base64 audio. It is the stubbed default TTS implementation.
type HTTPTTS struct {
	endpoint string
	apiKey   string
	client   *http.Client
	log      *slog.Logger
}

// HTTPOption customizes the client and logger of an HTTPSTT/HTTPTTS.
type HTTPOption func(*httpConfig)

type httpConfig struct {
	client *http.Client
	log    *slog.Logger
}

// WithHTTPClient sets the *http.Client used for the call; nil keeps the default.
func WithHTTPClient(c *http.Client) HTTPOption {
	return func(o *httpConfig) {
		if c != nil {
			o.client = c
		}
	}
}

// WithLogger sets the logger used on failures; nil keeps a discard logger.
func WithLogger(l *slog.Logger) HTTPOption {
	return func(o *httpConfig) {
		if l != nil {
			o.log = l
		}
	}
}

// NewHTTPSTT builds an HTTPSTT for the given endpoint and API key.
func NewHTTPSTT(endpoint, apiKey string, opts ...HTTPOption) *HTTPSTT {
	h := &httpConfig{client: defaultHTTPClient(), log: discardLogger()}
	for _, o := range opts {
		o(h)
	}
	return &HTTPSTT{endpoint: strings.TrimRight(endpoint, "/"), apiKey: apiKey, client: h.client, log: h.log}
}

// NewHTTPTTS builds an HTTPTTS for the given endpoint and API key.
func NewHTTPTTS(endpoint, apiKey string, opts ...HTTPOption) *HTTPTTS {
	h := &httpConfig{client: defaultHTTPClient(), log: discardLogger()}
	for _, o := range opts {
		o(h)
	}
	return &HTTPTTS{endpoint: strings.TrimRight(endpoint, "/"), apiKey: apiKey, client: h.client, log: h.log}
}

// sttRequest is the JSON body sent to the STT endpoint.
type sttRequest struct {
	Audio  string `json:"audio"`
	Format string `json:"format"`
}

// sttResponse is the transcription returned by the STT endpoint.
type sttResponse struct {
	Text string `json:"text"`
}

// STT posts the audio and returns the recognized text. A blank endpoint returns
// ErrNotConfigured so the chain degrades.
func (s *HTTPSTT) STT(ctx context.Context, audio Audio) (string, error) {
	if s.endpoint == "" {
		return "", ErrNotConfigured
	}
	if err := ctx.Err(); err != nil {
		return "", err
	}
	payload, err := json.Marshal(sttRequest{Audio: base64.StdEncoding.EncodeToString(audio.Data), Format: audio.Format})
	if err != nil {
		return "", fmt.Errorf("voice: %w: marshal: %v", ErrProviderFailed, err)
	}
	resp, err := postJSON(ctx, s.client, s.apiKey, s.endpoint, payload)
	if err != nil {
		return "", err
	}
	defer func() { _ = resp.Body.Close() }()
	var decoded sttResponse
	if err := json.NewDecoder(resp.Body).Decode(&decoded); err != nil {
		return "", fmt.Errorf("voice: %w: decode: %v", ErrProviderFailed, err)
	}
	return decoded.Text, nil
}

// ttsRequest is the JSON body sent to the TTS endpoint.
type ttsRequest struct {
	Text string `json:"text"`
}

// ttsResponse is the synthesized audio returned by the TTS endpoint.
type ttsResponse struct {
	Audio  string `json:"audio"`
	Format string `json:"format"`
}

// TTS posts the text and returns the decoded audio. A blank endpoint returns
// ErrNotConfigured so the chain degrades.
func (s *HTTPTTS) TTS(ctx context.Context, text string) (Audio, error) {
	if s.endpoint == "" {
		return Audio{}, ErrNotConfigured
	}
	if strings.TrimSpace(text) == "" {
		return Audio{}, ErrEmptyText
	}
	if err := ctx.Err(); err != nil {
		return Audio{}, err
	}
	payload, err := json.Marshal(ttsRequest{Text: text})
	if err != nil {
		return Audio{}, fmt.Errorf("voice: %w: marshal: %v", ErrProviderFailed, err)
	}
	resp, err := postJSON(ctx, s.client, s.apiKey, s.endpoint, payload)
	if err != nil {
		return Audio{}, err
	}
	defer func() { _ = resp.Body.Close() }()
	var decoded ttsResponse
	if err := json.NewDecoder(resp.Body).Decode(&decoded); err != nil {
		return Audio{}, fmt.Errorf("voice: %w: decode: %v", ErrProviderFailed, err)
	}
	data, err := base64.StdEncoding.DecodeString(decoded.Audio)
	if err != nil {
		return Audio{}, fmt.Errorf("voice: %w: decode audio: %v", ErrProviderFailed, err)
	}
	format := decoded.Format
	if format == "" {
		format = "mp3"
	}
	return Audio{Format: format, Data: data}, nil
}

// postJSON POSTs a JSON payload, wires auth, and checks the status code.
func postJSON(ctx context.Context, client *http.Client, apiKey, url string, payload []byte) (*http.Response, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(payload))
	if err != nil {
		return nil, fmt.Errorf("voice: %w: build: %v", ErrProviderFailed, err)
	}
	req.Header.Set("Content-Type", "application/json")
	if apiKey != "" {
		req.Header.Set("Authorization", "Bearer "+apiKey)
	}
	resp, err := client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("voice: %w: request: %v", ErrProviderFailed, err)
	}
	if resp.StatusCode != http.StatusOK {
		_ = resp.Body.Close()
		return nil, fmt.Errorf("voice: %w: status %d", ErrProviderFailed, resp.StatusCode)
	}
	return resp, nil
}

// defaultHTTPClient builds a client with a request timeout. A fresh client is
// returned per call rather than a package global, which the constraints forbid.
func defaultHTTPClient() *http.Client {
	return &http.Client{Transport: http.DefaultTransport, Timeout: cloudHTTPTimeout}
}

// discardLogger returns a logger that drops all output.
func discardLogger() *slog.Logger {
	return slog.New(slog.NewTextHandler(io.Discard, nil))
}

// newDashboardSTT returns the cloud STT adapter for a DashScope config. A call
// returns ErrNotConfigured when no API key is set so the chain degrades.
func newDashboardSTT(cfg config.VoiceConfig) STT {
	return NewDashscopeSTT(cfg)
}

// newDashboardTTS returns the cloud TTS adapter for a DashScope config.
func newDashboardTTS(cfg config.VoiceConfig) TTS {
	return NewDashscopeTTS(cfg)
}

// newDashboardCloner returns the cloud voice-enrollment cloner for a DashScope
// config, used by the create_voice (声音复刻) endpoint.
func newDashboardCloner(cfg config.VoiceConfig) VoiceCloner {
	return NewDashscopeCloner(cfg)
}

// newEdgeTTS returns the edge-tts adapter point (not yet implemented).
func newEdgeTTS() TTS { return notImplementedTTS{} }

// newEspeak returns the espeak adapter point (not yet implemented).
func newEspeak() TTS { return notImplementedTTS{} }

// notImplementedTTS is an adaptation point that always degrades.
type notImplementedTTS struct{}

func (notImplementedTTS) TTS(_ context.Context, _ string) (Audio, error) {
	return Audio{}, ErrNotImplemented
}