package portal

import (
	"bytes"
	"context"
	"crypto/rand"
	"crypto/sha256"
	"crypto/subtle"
	"encoding/hex"
	"encoding/json"
	"errors"
	"net/http"
	"net/http/httptest"
	"regexp"
	"strings"
	"time"

	"aigateway.local/core/internal/gateway"
	"aigateway.local/core/internal/identity"
	platformid "aigateway.local/core/internal/platform/id"
	"github.com/jackc/pgx/v5"
)

func regexpMust(pattern string) *regexp.Regexp { return regexp.MustCompile(pattern) }

// PersonalChannel 是门户用户自建的 webhook 渠道,绑定已批准模型。
// 入站消息经用户运行时凭据应答,用量归属用户自己的 Key。
type PersonalChannel struct {
	ID           string     `json:"id"`
	Code         string     `json:"code"`
	Name         string     `json:"name"`
	Kind         string     `json:"kind"`
	ProviderCode string     `json:"provider_code"`
	Model        string     `json:"model"`
	Enabled      bool       `json:"enabled"`
	LastUsedAt   *time.Time `json:"last_used_at,omitempty"`
	CreatedAt    time.Time  `json:"created_at"`
	UpdatedAt    time.Time  `json:"updated_at"`
}

const personalChannelSelect = `SELECT id::text,code,name,kind,provider_code,model,enabled,last_used_at,created_at,updated_at FROM gateway.personal_channels`

func scanPersonalChannel(row pgx.Row) (PersonalChannel, error) {
	var c PersonalChannel
	err := row.Scan(&c.ID, &c.Code, &c.Name, &c.Kind, &c.ProviderCode, &c.Model, &c.Enabled, &c.LastUsedAt, &c.CreatedAt, &c.UpdatedAt)
	return c, err
}

// PersonalChannels 返回当前用户的个人渠道。
func (s *Service) PersonalChannels(ctx context.Context, account identity.Account) ([]PersonalChannel, error) {
	rows, err := s.pool.Query(ctx, personalChannelSelect+` WHERE portal_user_id=$1 ORDER BY created_at DESC`, account.ID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	items := []PersonalChannel{}
	for rows.Next() {
		item, err := scanPersonalChannel(rows)
		if err != nil {
			return nil, err
		}
		items = append(items, item)
	}
	return items, rows.Err()
}

// CreatePersonalChannel 创建 webhook 个人渠道并返回入站令牌(仅此一次显示)。
func (s *Service) CreatePersonalChannel(ctx context.Context, account identity.Account, code, name, providerCode, model string) (PersonalChannel, string, error) {
	code = strings.ToLower(strings.TrimSpace(code))
	name = strings.TrimSpace(name)
	if !personalChannelCodePattern.MatchString(code) || name == "" || len(name) > 128 {
		return PersonalChannel{}, "", errors.New("渠道代码或名称无效")
	}
	if _, err := s.approvedModel(ctx, account, providerCode, model); err != nil {
		return PersonalChannel{}, "", errors.New("模型未批准或不可用，请先在「模型权限」申请")
	}
	// 聊天依赖用户运行时凭据,先确保开通。
	if _, err := s.ensureChatCredential(ctx, account); err != nil {
		return PersonalChannel{}, "", err
	}
	token, err := randomToken(32)
	if err != nil {
		return PersonalChannel{}, "", err
	}
	id, err := platformid.NewUUID()
	if err != nil {
		return PersonalChannel{}, "", err
	}
	hash := channelTokenHash(token)
	_, err = s.pool.Exec(ctx, `INSERT INTO gateway.personal_channels(id,portal_user_id,code,name,kind,inbound_token_hash,provider_code,model) VALUES($1,$2,$3,$4,'webhook',$5,$6,$7)`, id, account.ID, code, name, hash, providerCode, model)
	if err != nil {
		if isUniqueViolation(err) {
			return PersonalChannel{}, "", errors.New("渠道代码已存在")
		}
		return PersonalChannel{}, "", err
	}
	item, err := scanPersonalChannel(s.pool.QueryRow(ctx, personalChannelSelect+` WHERE id=$1`, id))
	return item, token, err
}

// RegenerateToken 轮换入站令牌(旧令牌立即失效)。
func (s *Service) RegenerateToken(ctx context.Context, account identity.Account, id string) (string, error) {
	token, err := randomToken(32)
	if err != nil {
		return "", err
	}
	tag, err := s.pool.Exec(ctx, `UPDATE gateway.personal_channels SET inbound_token_hash=$3,updated_at=clock_timestamp() WHERE id=$1 AND portal_user_id=$2`, id, account.ID, channelTokenHash(token))
	if err != nil {
		return "", err
	}
	if tag.RowsAffected() == 0 {
		return "", ErrNotFound
	}
	return token, nil
}

// DeletePersonalChannel 删除个人渠道(仅本人)。
func (s *Service) DeletePersonalChannel(ctx context.Context, account identity.Account, id string) error {
	tag, err := s.pool.Exec(ctx, `DELETE FROM gateway.personal_channels WHERE id=$1 AND portal_user_id=$2`, id, account.ID)
	if err != nil {
		return err
	}
	if tag.RowsAffected() == 0 {
		return ErrNotFound
	}
	return nil
}

// HandlePersonalInbound 处理个人渠道入站消息:令牌校验 → 用户运行时凭据应答。
func (s *Service) HandlePersonalInbound(ctx context.Context, code, presentedToken, text string) (string, error) {
	code = strings.ToLower(strings.TrimSpace(code))
	text = strings.TrimSpace(text)
	if code == "" || presentedToken == "" {
		return "", errors.New("渠道代码或令牌缺失")
	}
	if text == "" || len(text) > 100000 {
		return "", errors.New("消息为空或过长")
	}
	var id, userID, providerCode, model, tokenHash string
	err := s.pool.QueryRow(ctx, `SELECT id::text,portal_user_id::text,provider_code,model,inbound_token_hash FROM gateway.personal_channels WHERE code=$1 AND enabled`, code).Scan(&id, &userID, &providerCode, &model, &tokenHash)
	if errors.Is(err, pgx.ErrNoRows) {
		// 与令牌无效同一文案,不泄露渠道存在性。
		return "", errors.New("入站令牌无效")
	}
	if err != nil {
		return "", err
	}
	if subtle.ConstantTimeCompare([]byte(channelTokenHash(presentedToken)), []byte(tokenHash)) != 1 {
		return "", errors.New("入站令牌无效")
	}
	if s.credentials == nil || s.gateway == nil {
		return "", errors.New("渠道服务未配置")
	}
	secret, _, err := s.credentials.UserSecret(ctx, userID)
	if err != nil {
		return "", err
	}
	if secret == "" {
		return "", errors.New("用户运行时凭据未开通")
	}
	payload, _ := json.Marshal(map[string]any{"model": model, "messages": []map[string]any{{"role": "user", "content": text}}, "stream": false})
	request := httptest.NewRequest(http.MethodPost, "/v1/chat/completions", bytes.NewReader(payload)).WithContext(gateway.WithRequestID(ctx, "personal-channel-"+time.Now().UTC().Format("20060102150405.000000000")))
	request.Header.Set("Authorization", "Bearer "+secret)
	request.Header.Set("Content-Type", "application/json")
	recorder := httptest.NewRecorder()
	s.gateway.ServeHTTP(recorder, request)
	var response map[string]any
	if err := json.Unmarshal(recorder.Body.Bytes(), &response); err != nil {
		return "", errors.New("模型响应无法解析")
	}
	if recorder.Code < 200 || recorder.Code >= 300 {
		message := "模型调用失败"
		if value, ok := response["error"].(map[string]any); ok {
			if text, ok := value["message"].(string); ok {
				message = text
			}
		}
		return "", errors.New(message)
	}
	choices, _ := response["choices"].([]any)
	if len(choices) == 0 {
		return "", errors.New("模型未返回回答")
	}
	choice, _ := choices[0].(map[string]any)
	message, _ := choice["message"].(map[string]any)
	answer, _ := message["content"].(string)
	if strings.TrimSpace(answer) == "" {
		return "", errors.New("模型未返回文本回答")
	}
	_, _ = s.pool.Exec(ctx, `UPDATE gateway.personal_channels SET last_used_at=clock_timestamp() WHERE id=$1`, id)
	return answer, nil
}

func channelTokenHash(token string) string {
	sum := sha256.Sum256([]byte(token))
	return hex.EncodeToString(sum[:])
}

func randomToken(size int) (string, error) {
	buf := make([]byte, size)
	if _, err := rand.Read(buf); err != nil {
		return "", err
	}
	return hex.EncodeToString(buf), nil
}

var personalChannelCodePattern = regexpMust(`^[a-z][a-z0-9_-]{2,63}$`)