use std::{
    collections::BTreeMap,
    env,
    fs,
    path::{Path, PathBuf},
};

use serde_json::{Map, Value};

const APP_NAME: &str = "com.ziyun.callclient";
const CONFIG_FILE_NAME: &str = "config.json";

fn get_home_dir() -> PathBuf {
    if let Ok(value) = env::var("HOME") {
        return PathBuf::from(value);
    }

    if let Ok(value) = env::var("USERPROFILE") {
        return PathBuf::from(value);
    }

    PathBuf::from(".")
}

fn get_config_dir() -> PathBuf {
    if cfg!(target_os = "linux") {
        if let Ok(value) = env::var("XDG_CONFIG_HOME") {
            return PathBuf::from(value).join(APP_NAME);
        }

        return get_home_dir().join(".config").join(APP_NAME);
    }

    if let Ok(value) = env::var("APPDATA") {
        return PathBuf::from(value).join(APP_NAME);
    }

    get_home_dir().join(".").join(APP_NAME)
}

fn get_config_file_path() -> PathBuf {
    get_config_dir().join(CONFIG_FILE_NAME)
}

fn ensure_parent_dir(path: &Path) -> Result<(), String> {
    let Some(parent) = path.parent() else {
        return Ok(());
    };

    fs::create_dir_all(parent).map_err(|error| format!("创建配置目录失败: {error}"))
}

fn read_config() -> Result<Value, String> {
    let path = get_config_file_path();

    if !path.exists() {
        return Ok(Value::Object(Map::new()));
    }

    let content = fs::read_to_string(&path).map_err(|error| format!("读取配置文件失败: {error}"))?;
    if content.trim().is_empty() {
        return Ok(Value::Object(Map::new()));
    }

    serde_json::from_str::<Value>(&content).map_err(|error| format!("解析配置文件失败: {error}"))
}

fn write_config(value: &Value) -> Result<(), String> {
    let path = get_config_file_path();
    ensure_parent_dir(&path)?;
    let content = serde_json::to_string_pretty(value).map_err(|error| format!("序列化配置失败: {error}"))?;
    fs::write(path, content).map_err(|error| format!("写入配置文件失败: {error}"))
}

fn merge_value(target: &mut Value, patch: Value) {
    match (target, patch) {
        (Value::Object(target_map), Value::Object(patch_map)) => {
            for (key, value) in patch_map {
                if let Some(existing) = target_map.get_mut(&key) {
                    merge_value(existing, value);
                } else {
                    target_map.insert(key, value);
                }
            }
        }
        (target_value, patch_value) => {
            *target_value = patch_value;
        }
    }
}

#[tauri::command]
pub fn config_get_all() -> Result<BTreeMap<String, Value>, String> {
    let value = read_config()?;
    let Value::Object(map) = value else {
        return Ok(BTreeMap::new());
    };

    Ok(map.into_iter().collect())
}

#[tauri::command]
pub fn config_merge(partial: Value) -> Result<BTreeMap<String, Value>, String> {
    let mut current = read_config()?;
    merge_value(&mut current, partial);
    write_config(&current)?;

    let Value::Object(map) = current else {
        return Ok(BTreeMap::new());
    };

    Ok(map.into_iter().collect())
}