//! Configuration file support for TLI
//!
//! This module provides configuration file management for TLI client settings.
//! Configuration is loaded from `~/.foxhunt/config.toml` and can be overridden
//! by CLI arguments (following standard CLI precedence).
//!
//! ## Precedence
//! CLI arguments > Config file > Defaults
//!
//! ## Example Config File
//! ```toml
//! # ~/.foxhunt/config.toml
//! api_gateway_url = "http://localhost:50051"
//! log_level = "info"
//! token_storage = "keyring"
//! ```

use anyhow::{Context, Result};
use serde::{Deserialize, Serialize};
use std::path::PathBuf;

/// TLI configuration structure
///
/// Contains all configurable settings for the TLI client application.
/// Settings can be loaded from `~/.foxhunt/config.toml` and overridden
/// by CLI arguments or environment variables.
#[derive(Debug, Serialize, Deserialize)]
pub struct TliConfig {
    /// API Gateway URL (default: <http://localhost:50051>)
    #[serde(default = "default_api_gateway_url")]
    pub api_gateway_url: String,

    /// Log level (default: info)
    #[serde(default = "default_log_level")]
    pub log_level: String,

    /// Token storage backend (default: keyring)
    #[serde(default = "default_token_storage")]
    pub token_storage: String,
}

fn default_api_gateway_url() -> String {
    "http://localhost:50051".to_owned()
}

fn default_log_level() -> String {
    "info".to_owned()
}

fn default_token_storage() -> String {
    "keyring".to_owned()
}

impl Default for TliConfig {
    fn default() -> Self {
        Self {
            api_gateway_url: default_api_gateway_url(),
            log_level: default_log_level(),
            token_storage: default_token_storage(),
        }
    }
}

impl TliConfig {
    /// Load config from ~/.foxhunt/config.toml
    ///
    /// Returns default configuration if file doesn't exist.
    /// Returns error if file exists but is malformed.
    ///
    /// # Examples
    /// ```no_run
    /// use tli::config::TliConfig;
    ///
    /// let config = TliConfig::load().unwrap();
    /// println!("API Gateway: {}", config.api_gateway_url);
    /// ```
    pub fn load() -> Result<Self> {
        let config_path = Self::config_path()?;

        if !config_path.exists() {
            // Return defaults if no config file
            return Ok(Self::default());
        }

        let content =
            std::fs::read_to_string(&config_path).context("Failed to read config file")?;

        let config: Self = toml::from_str(&content).context("Failed to parse config file")?;

        Ok(config)
    }

    /// Save config to ~/.foxhunt/config.toml
    ///
    /// Creates parent directory if it doesn't exist.
    ///
    /// # Examples
    /// ```no_run
    /// use tli::config::TliConfig;
    ///
    /// let config = TliConfig {
    ///     api_gateway_url: "http://localhost:50051".to_string(),
    ///     log_level: "debug".to_string(),
    ///     token_storage: "keyring".to_string(),
    /// };
    /// config.save().unwrap();
    /// ```
    pub fn save(&self) -> Result<()> {
        let config_path = Self::config_path()?;

        // Create parent directory if needed
        if let Some(parent) = config_path.parent() {
            std::fs::create_dir_all(parent)?;
        }

        let content = toml::to_string_pretty(self).context("Failed to serialize config")?;

        std::fs::write(&config_path, content).context("Failed to write config file")?;

        Ok(())
    }

    /// Get config file path: ~/.foxhunt/config.toml
    ///
    /// # Errors
    /// Returns error if home directory cannot be determined
    fn config_path() -> Result<PathBuf> {
        let home = dirs::home_dir().ok_or_else(|| anyhow::anyhow!("Cannot find home directory"))?;

        Ok(home.join(".foxhunt").join("config.toml"))
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_default_config() {
        // Test that Default trait provides correct values
        let config = TliConfig::default();
        assert_eq!(config.api_gateway_url, "http://localhost:50051");
        assert_eq!(config.log_level, "info");
        assert_eq!(config.token_storage, "keyring");
    }

    #[test]
    fn test_config_serialization() {
        let config = TliConfig {
            api_gateway_url: "http://example.com:50051".to_owned(),
            log_level: "debug".to_owned(),
            token_storage: "file".to_owned(),
        };

        let toml_str = toml::to_string(&config).unwrap();
        let parsed: TliConfig = toml::from_str(&toml_str).unwrap();

        assert_eq!(config.api_gateway_url, parsed.api_gateway_url);
        assert_eq!(config.log_level, parsed.log_level);
        assert_eq!(config.token_storage, parsed.token_storage);
    }

    #[test]
    fn test_load_nonexistent_config() {
        // This should return default config without error when file doesn't exist
        let result = TliConfig::load();
        assert!(result.is_ok());
        let config = result.unwrap();

        // When config file doesn't exist, load() returns Self::default()
        // which should have all default values
        assert_eq!(config.api_gateway_url, "http://localhost:50051");
        assert_eq!(config.log_level, "info");
        assert_eq!(config.token_storage, "keyring");
    }

    #[test]
    fn test_serde_defaults() {
        // Test that empty TOML string deserializes to defaults
        let empty_toml = "";
        let config: TliConfig = toml::from_str(empty_toml).unwrap();
        assert_eq!(config.api_gateway_url, "http://localhost:50051");
        assert_eq!(config.log_level, "info");
        assert_eq!(config.token_storage, "keyring");
    }
}