use std::path::PathBuf;
use anyhow::{Result, bail};

/// Server configuration loaded from environment variables.
#[derive(Debug, Clone)]
pub struct Config {
    /// Bind address, e.g. "0.0.0.0:9432"
    pub bind: String,
    /// API key for Bearer auth
    pub api_key: String,
    /// Path to SQLite database file
    pub db_path: PathBuf,
    /// User-Agent header for OpenFood Facts API requests
    pub off_user_agent: String,
}

impl Config {
    pub fn from_env() -> Result<Self> {
        let bind = std::env::var("NUTRITION_MCP_BIND")
            .unwrap_or_else(|_| "0.0.0.0:9432".to_string());

        let api_key = std::env::var("NUTRITION_MCP_API_KEY")
            .unwrap_or_else(|_| {
                tracing::warn!("NUTRITION_MCP_API_KEY not set — generating a random key");
                uuid::Uuid::new_v4().to_string()
            });

        let db_path = std::env::var("NUTRITION_MCP_DB_PATH")
            .map(PathBuf::from)
            .unwrap_or_else(|_| {
                let mut p = dirs_data_path();
                p.push("nutrition");
                p.push("nutrition.db");
                p
            });

        let off_user_agent = std::env::var("NUTRITION_MCP_OFF_USER_AGENT")
            .unwrap_or_else(|_| {
                "NutritionMCP/0.1.0 (personal use)".to_string()
            });

        if api_key.is_empty() {
            bail!("NUTRITION_MCP_API_KEY must not be empty");
        }

        Ok(Self {
            bind,
            api_key,
            db_path,
            off_user_agent,
        })
    }

    /// Create the parent directory of db_path if it doesn't exist.
    pub fn ensure_db_dir(&self) -> Result<()> {
        if let Some(parent) = self.db_path.parent() {
            std::fs::create_dir_all(parent)?;
        }
        Ok(())
    }
}

fn dirs_data_path() -> PathBuf {
    // Prefer XDG_DATA_HOME, fall back to ~/.local/share
    std::env::var("XDG_DATA_HOME")
        .map(PathBuf::from)
        .unwrap_or_else(|_| {
            let home = std::env::var("HOME").unwrap_or_else(|_| ".".to_string());
            let mut p = PathBuf::from(home);
            p.push(".local");
            p.push("share");
            p
        })
}