package intelligence_finance

import (
	"crypto/hmac"
	"crypto/rand"
	"crypto/sha256"
	"encoding/base64"
	"fmt"
	"math/big"
	"sort"
	"strings"
	"time"
)

// GenerateTimestamp generates a Unix timestamp in seconds as a string.
func GenerateTimestamp() string {
	return fmt.Sprintf("%d", time.Now().Unix())
}

// GenerateTimestampMillis generates a Unix timestamp in milliseconds as a string.
func GenerateTimestampMillis() string {
	return fmt.Sprintf("%d", time.Now().UnixMilli())
}

// GenerateNonce generates a cryptographically secure random string of the given length.
func GenerateNonce(length int) (string, error) {
	const charset = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
	b := make([]byte, length)
	for i := range b {
		num, err := rand.Int(rand.Reader, big.NewInt(int64(len(charset))))
		if err != nil {
			return "", fmt.Errorf("generate nonce: %w", err)
		}
		b[i] = charset[num.Int64()]
	}
	return string(b), nil
}

// HmacSHA256Base64 computes HmacSHA256 of the given data using the secret key,
// and returns the result as a Base64-encoded string.
func HmacSHA256Base64(secret, data string) string {
	mac := hmac.New(sha256.New, []byte(secret))
	mac.Write([]byte(data))
	return base64.StdEncoding.EncodeToString(mac.Sum(nil))
}

// BuildSignString sorts parameters by key in dictionary order and concatenates
// them as key=value&key2=value2, excluding empty values and the sign/signature fields.
func BuildSignString(params map[string]string) string {
	keys := make([]string, 0, len(params))
	for k, v := range params {
		if v != "" && k != "sign" && k != "signature" {
			keys = append(keys, k)
		}
	}
	sort.Strings(keys)

	var parts []string
	for _, k := range keys {
		parts = append(parts, fmt.Sprintf("%s=%s", k, params[k]))
	}
	return strings.Join(parts, "&")
}

// BuildSignStringOrdered concatenates parameters in the specified key order,
// excluding empty values.
func BuildSignStringOrdered(params map[string]string, orderedKeys []string) string {
	var parts []string
	for _, k := range orderedKeys {
		if v, ok := params[k]; ok && v != "" {
			parts = append(parts, fmt.Sprintf("%s=%s", k, v))
		}
	}
	return strings.Join(parts, "&")
}