// Package miot provides MIoT core client for Xiaomi Home devices.
// This file is a direct port of py-miot/common.py utility functions.
package miot

import (
	"crypto/sha1"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"math/rand"
	"os"
	"path/filepath"
	"regexp"
	"strings"

	"gopkg.in/yaml.v3"
)

// ============================================================================
// RootPath (aligned with Python MIOT_ROOT_PATH)
// ============================================================================

// RootPath is the root directory of the miot package.
// It mirrors Python's MIOT_ROOT_PATH = path.dirname(path.abspath(__file__)).
// Callers should set this before using GenAbsolutePath.
var RootPath string

func init() {
	// Attempt to discover the project root from the working directory.
	// Callers may override this after init.
	if wd, err := os.Getwd(); err == nil {
		RootPath = wd
	}
}

// ============================================================================
// Utility functions (aligned with py-miot/common.py)
// ============================================================================

// GenAbsolutePath generates an absolute path relative to RootPath.
// Aligns with Python: gen_absolute_path(relative_path).
func GenAbsolutePath(relativePath string) string {
	return filepath.Join(RootPath, relativePath)
}

// CalcGroupID calculates a group ID from a user ID and home ID.
// Uses SHA1 with a "central_service" salt, returning the first 16 hex chars.
// Aligns with Python: calc_group_id(uid, home_id).
func CalcGroupID(uid, homeID string) string {
	src := fmt.Sprintf("%scentral_service%s", uid, homeID)
	h := sha1.Sum([]byte(src))
	return hex.EncodeToString(h[:])[:16]
}

// LoadJSONFile loads and parses a JSON file.
// Aligns with Python: load_json_file(json_file).
func LoadJSONFile(filePath string) (map[string]interface{}, error) {
	data, err := os.ReadFile(filePath)
	if err != nil {
		return nil, fmt.Errorf("read JSON file %s: %w", filePath, err)
	}
	var result map[string]interface{}
	if err := json.Unmarshal(data, &result); err != nil {
		return nil, fmt.Errorf("parse JSON file %s: %w", filePath, err)
	}
	return result, nil
}

// LoadYAMLFile loads and parses a YAML file.
// Aligns with Python: load_yaml_file(yaml_file).
func LoadYAMLFile(filePath string) (map[string]interface{}, error) {
	data, err := os.ReadFile(filePath)
	if err != nil {
		return nil, fmt.Errorf("read YAML file %s: %w", filePath, err)
	}
	var result map[string]interface{}
	if err := yaml.Unmarshal(data, &result); err != nil {
		return nil, fmt.Errorf("parse YAML file %s: %w", filePath, err)
	}
	return result, nil
}

// RandomizeInt randomizes an integer within the given ratio range.
// Formula: int(value * (1 - ratio + random() * 2 * ratio))
// Aligns with Python: randomize_int(value, ratio).
func RandomizeInt(value int, ratio float64) int {
	return int(float64(value) * (1 - ratio + rand.Float64()*2*ratio))
}

// RandomizeFloat randomizes a float64 within the given ratio range.
// Formula: value * (1 - ratio + random() * 2 * ratio)
// Aligns with Python: randomize_float(value, ratio).
func RandomizeFloat(value float64, ratio float64) float64 {
	return value * (1 - ratio + rand.Float64()*2*ratio)
}

// ============================================================================
// Slugify (aligned with py-miot/common.py slugify_name / slugify_did)
// ============================================================================

// nonAlphaNum matches sequences of non-alphanumeric characters.
var nonAlphaNum = regexp.MustCompile(`[^a-z0-9]+`)

// SlugifyName converts a name to a lowercase slug with underscore separators.
// Aligns with Python: slugify_name(name, separator='_').
func SlugifyName(name string) string {
	s := strings.ToLower(name)
	s = nonAlphaNum.ReplaceAllString(s, "_")
	s = strings.Trim(s, "_")
	return s
}

// SlugifyDID creates a slug from a cloud server and device ID.
// Pattern: f"{cloud_server}_{did}" then slugify.
// Aligns with Python: slugify_did(cloud_server, did).
func SlugifyDID(cloudServer, did string) string {
	return SlugifyName(cloudServer + "_" + did)
}