package upstreamimpl

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"strings"
	"time"
)

const (
	tengyuOneLinkTokenPath = "/prod-api/open/api/oneLinkToken"
	tengyuTokenTTL         = time.Hour
)

// OneLinkToken is the value returned by a shared-token fetcher.
type OneLinkToken struct {
	Value     string
	CreatedAt time.Time
	ExpiresAt time.Time
}

// TokenFetcher mirrors the token core fetch boundary. chanKey is the
// protocol's c_no; it is never inferred from unrelated channel fields.
type TokenFetcher interface {
	FetchToken(context.Context, string) (OneLinkToken, error)
}

// TokenProvider is the consumer-facing token core boundary.
type TokenProvider interface {
	GetToken(context.Context, string) (string, error)
}

// TengyuTokenConfig contains all values required by the Tengyu protocol.
// The provider intentionally does not infer these values from channel config.
type TengyuTokenConfig struct {
	BaseURL   string
	Path      string
	PwdKey    string
	ChannelNo string
	Timeout   time.Duration
}

// TengyuTokenProvider fetches a Tengyu shared OneLink token.
type TengyuTokenProvider struct {
	baseURL   string
	path      string
	pwdKey    string
	channelNo string
	client    *http.Client
}

type tengyuTokenResponse struct {
	Code int             `json:"code"`
	Msg  string          `json:"msg"`
	Data json.RawMessage `json:"data"`
}

func NewTengyuTokenProvider(config TengyuTokenConfig) *TengyuTokenProvider {
	return &TengyuTokenProvider{
		baseURL:   strings.TrimRight(strings.TrimSpace(config.BaseURL), "/"),
		path:      normalizeProviderPath(config.Path, tengyuOneLinkTokenPath),
		pwdKey:    config.PwdKey,
		channelNo: config.ChannelNo,
		client:    newTengyuHTTPClient(config.Timeout),
	}
}

// Historical in-package names are retained as a small adapter for callers
// that constructed the provider before the token-core interfaces were named.
type tengyuTokenConfig = TengyuTokenConfig

func newTengyuTokenProvider(config tengyuTokenConfig) *TengyuTokenProvider {
	return NewTengyuTokenProvider(config)
}

func newTengyuHTTPClient(timeout time.Duration) *http.Client {
	if timeout <= 0 {
		timeout = defaultUpstreamHTTPTimeout
	}
	return &http.Client{Timeout: timeout}
}

func (p *TengyuTokenProvider) Fetch(ctx context.Context) (OneLinkToken, error) {
	return p.fetch(ctx, p.channelNo)
}

func (p *TengyuTokenProvider) FetchToken(ctx context.Context, channelNo string) (OneLinkToken, error) {
	if strings.TrimSpace(channelNo) == "" {
		channelNo = p.channelNo
	}
	return p.fetch(ctx, channelNo)
}

func (p *TengyuTokenProvider) GetToken(ctx context.Context, channelNo string) (string, error) {
	token, err := p.FetchToken(ctx, channelNo)
	if err != nil {
		return "", err
	}
	return token.Value, nil
}

func (p *TengyuTokenProvider) fetch(ctx context.Context, channelNo string) (OneLinkToken, error) {
	if p == nil || p.client == nil {
		return OneLinkToken{}, fmt.Errorf("tengyu token provider is not initialized")
	}
	if p.baseURL == "" {
		return OneLinkToken{}, fmt.Errorf("tengyu token base URL is required")
	}
	if strings.TrimSpace(p.pwdKey) == "" {
		return OneLinkToken{}, fmt.Errorf("tengyu pwdkey is required")
	}
	if strings.TrimSpace(channelNo) == "" {
		return OneLinkToken{}, fmt.Errorf("tengyu channel number is required")
	}

	endpoint, err := url.Parse(joinProviderURL(p.baseURL, p.path))
	if err != nil {
		return OneLinkToken{}, fmt.Errorf("parse Tengyu token URL: %w", err)
	}
	query := endpoint.Query()
	query.Set("pwdkey", p.pwdKey)
	query.Set("c_no", channelNo)
	endpoint.RawQuery = query.Encode()

	req, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint.String(), nil)
	if err != nil {
		return OneLinkToken{}, fmt.Errorf("create Tengyu token request: %w", err)
	}
	req.Header.Set("Accept", "application/json")
	resp, err := p.client.Do(req)
	if err != nil {
		return OneLinkToken{}, fmt.Errorf("request Tengyu token: %w", err)
	}
	defer resp.Body.Close()
	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return OneLinkToken{}, fmt.Errorf("read Tengyu token response: %w", err)
	}
	if resp.StatusCode < http.StatusOK || resp.StatusCode >= http.StatusMultipleChoices {
		return OneLinkToken{}, fmt.Errorf("Tengyu token HTTP status %d: %s", resp.StatusCode, strings.TrimSpace(string(body)))
	}

	var output tengyuTokenResponse
	if err := json.Unmarshal(body, &output); err != nil {
		return OneLinkToken{}, fmt.Errorf("decode Tengyu token response: %w", err)
	}
	if output.Code != http.StatusOK {
		return OneLinkToken{}, fmt.Errorf("Tengyu token failed: code=%d, message=%s", output.Code, output.Msg)
	}
	var value string
	if err := json.Unmarshal(output.Data, &value); err != nil {
		return OneLinkToken{}, fmt.Errorf("decode Tengyu shared token: %w", err)
	}
	if strings.TrimSpace(value) == "" {
		return OneLinkToken{}, fmt.Errorf("Tengyu shared token is empty")
	}

	now := time.Now()
	return OneLinkToken{Value: value, CreatedAt: now, ExpiresAt: now.Add(tengyuTokenTTL)}, nil
}