use std::{env, fs::read_to_string, path::PathBuf};
use directories::ProjectDirs;
use uuid::Uuid;

use super::{file::FileConfig, runtime::RuntimeConfig};
use crate::{constants::*, errors::McError};

pub struct ConfigLoader;

impl ConfigLoader {
    pub fn load(cfg_file: Option<&PathBuf>) -> Result<RuntimeConfig, McError> {
        let path = match cfg_file {
            | Some(p) => p.clone(),
            | None => Self::default_config_path()?,
        };

        let mut file_cfg = if path.exists() {
            Self::read_file(&path)?
        } else {
            Self::default_file_config()?
        };

        Self::apply_env_overrides(&mut file_cfg);

        Ok(RuntimeConfig::from_file(file_cfg))
    }

    fn read_file(path: &PathBuf) -> Result<FileConfig, McError> {
        let content = read_to_string(path).map_err(|e| {
            McError::Config(format!(
                "Failed to read config file {}: {}",
                path.display(),
                e
            ))
        })?;

        toml::from_str(&content).map_err(|e| {
            McError::Config(format!("Failed to parse config file: {}", e))
        })
    }

    fn apply_env_overrides(cfg: &mut FileConfig) {
        cfg.username = env::var(ENV_USERNAME)
            .unwrap_or_else(|_| DEFAULT_USERNAME.to_string());

        cfg.version = env::var(ENV_VERSION)
            .unwrap_or_else(|_| DEFAULT_VERSION.to_string());

        cfg.java_path = env::var(ENV_JAVA_PATH)
            .unwrap_or_else(|_| DEFAULT_JAVA_PATH.to_string());

        cfg.max_memory_mb = env::var(ENV_MAX_MEMORY_MB)
            .ok()
            .and_then(|v| v.parse().ok())
            .unwrap_or(DEFAULT_MAX_MEMORY_MB);
    }

    fn default_config_path() -> Result<PathBuf, McError> {
        let base = ProjectDirs::from(
            DEFAULT_COMPANY,
            DEFAULT_PROJECT_GROUP,
            DEFAULT_PROJECT_NAME,
        )
        .ok_or_else(|| McError::Config(DEFAULT_ERR_PLATFORM_DIR.into()))?;

        Ok(base.config_dir().join(DEFAULT_CONFIG_FILENAME))
    }

    fn default_file_config() -> Result<FileConfig, McError> {
        let base = ProjectDirs::from(
            DEFAULT_COMPANY,
            DEFAULT_PROJECT_GROUP,
            DEFAULT_PROJECT_NAME,
        )
        .ok_or_else(|| McError::Config(DEFAULT_ERR_PLATFORM_DIR.into()))?;

        Ok(FileConfig {
            username: DEFAULT_USERNAME.into(),
            uuid: Uuid::new_v4().to_string(),
            version: DEFAULT_VERSION.into(),
            max_memory_mb: DEFAULT_MAX_MEMORY_MB,
            java_path: DEFAULT_JAVA_PATH.into(),
            data_dir: base.data_dir().into(),
            // cache_dir: base.cache_dir().into(),
            // config_dir: base.config_dir().into(),
            jvm_args: vec![],
            runtimes: vec![],
        })
    }
}