soar-utils 0.4.1

use std::{env, path::PathBuf};

use crate::{
    error::{PathError, PathResult},
    system::get_username,
};

/// Resolves a path string that may contain environment variables
///
/// This method expands environment variables in the format `$VAR` or `${VAR}`, resolves tilde
/// (`~`) to the user's home directory when it appears at the start of the path, and converts
/// relative paths to absolute paths based on the current working directory.
///
/// # Arguments
///
/// * `path` - The path string that may contain environment variables and tilde expansion
///
/// # Returns
///
/// Returns an absolute [`PathBuf`] with all variables expanded, or a [`PathError`] if the path
/// is invalid or variables cannot be resolved.
///
/// # Errors
///
/// * [`PathError::Empty`] if the path is empty
/// * [`PathError::CurrentDir`] if the current directory cannot be determined
/// * [`PathError::MissingEnvVar`] if the environment variables are undefined
///
/// # Example
///
/// ```
/// use soar_utils::error::PathResult;
/// use soar_utils::path::resolve_path;
///
/// fn main() -> PathResult<()> {
///     let resolved = resolve_path("$HOME/path/to/file")?;
///     println!("Resolved path is {:#?}", resolved);
///     Ok(())
/// }
/// ```
pub fn resolve_path(path: &str) -> PathResult<PathBuf> {
    let path = path.trim();

    if path.is_empty() {
        return Err(PathError::Empty);
    }

    let resolved = expand_variables(path)?;
    let path_buf = PathBuf::from(resolved);

    if path_buf.is_absolute() {
        Ok(path_buf)
    } else {
        env::current_dir()
            .map(|cwd| cwd.join(path_buf))
            .map_err(|err| {
                PathError::FailedToGetCurrentDir {
                    source: err,
                }
            })
    }
}

/// Returns the user's home directory
///
/// This method first checks the `HOME` environment variables. If not set, it falls back to
/// constructing the path `/home/{username}` where username is obtained from the system.
///
/// # Example
///
/// ```
/// use soar_utils::path::home_dir;
///
/// let home = home_dir();
/// println!("Home dir is {:#?}", home);
/// ```
pub fn home_dir() -> PathBuf {
    env::var("HOME")
        .map(PathBuf::from)
        .unwrap_or_else(|_| PathBuf::from(format!("/home/{}", get_username())))
}

/// Returns the user's config directory following XDG Base Directory Specification
///
/// This method checks the `XDG_CONFIG_HOME` environment variable. If not set, it defaults to
/// `$HOME/.config`
///
/// # Example
///
/// ```
/// use soar_utils::path::xdg_config_home;
///
/// let config = xdg_config_home();
/// println!("Config dir is {:#?}", config);
/// ```
pub fn xdg_config_home() -> PathBuf {
    env::var("XDG_CONFIG_HOME")
        .map(PathBuf::from)
        .unwrap_or_else(|_| home_dir().join(".config"))
}

/// Returns the user's data directory following XDG Base Directory Specification
///
/// This method checks the `XDG_DATA_HOME` environment variable. If not set, it defaults to
/// `$HOME/.local/share`
///
/// # Example
///
/// ```
/// use soar_utils::path::xdg_data_home;
///
/// let data = xdg_data_home();
/// println!("Data dir is {:#?}", data);
/// ```
pub fn xdg_data_home() -> PathBuf {
    env::var("XDG_DATA_HOME")
        .map(PathBuf::from)
        .unwrap_or_else(|_| home_dir().join(".local/share"))
}

/// Returns the user's cache directory following XDG Base Directory Specification
///
/// This method checks the `XDG_CACHE_HOME` environment variable. If not set, it defaults to
/// `$HOME/.cache`
///
/// # Example
///
/// ```
/// use soar_utils::path::xdg_cache_home;
///
/// let cache = xdg_cache_home();
/// println!("Cache dir is {:#?}", cache);
/// ```
pub fn xdg_cache_home() -> PathBuf {
    env::var("XDG_CACHE_HOME")
        .map(PathBuf::from)
        .unwrap_or_else(|_| home_dir().join(".cache"))
}

/// Returns the desktop directory
pub fn desktop_dir(system: bool) -> PathBuf {
    if system {
        PathBuf::from("/usr/local/share/applications")
    } else {
        xdg_data_home().join("applications")
    }
}

/// Returns the icons directory
pub fn icons_dir(system: bool) -> PathBuf {
    if system {
        PathBuf::from("/usr/local/share/icons/hicolor")
    } else {
        xdg_data_home().join("icons/hicolor")
    }
}

fn expand_variables(path: &str) -> PathResult<String> {
    let mut result = String::with_capacity(path.len());
    let mut chars = path.chars().peekable();

    while let Some(c) = chars.next() {
        match c {
            '$' => {
                if chars.peek() == Some(&'{') {
                    chars.next();
                    let var_name = consume_until(&mut chars, '}')?;
                    expand_env_var(&var_name, &mut result, path)?;
                } else {
                    let var_name = consume_var_name(&mut chars);
                    if var_name.is_empty() {
                        result.push('$');
                    } else {
                        expand_env_var(&var_name, &mut result, path)?;
                    }
                }
            }
            '~' if result.is_empty() => result.push_str(&home_dir().to_string_lossy()),
            _ => result.push(c),
        }
    }

    Ok(result)
}

fn consume_until(
    chars: &mut std::iter::Peekable<std::str::Chars>,
    delimiter: char,
) -> PathResult<String> {
    let mut var_name = String::new();

    for c in chars.by_ref() {
        if c == delimiter {
            return Ok(var_name);
        }
        var_name.push(c);
    }

    Err(PathError::UnclosedVariable {
        input: format!("${{{var_name}"),
    })
}

fn consume_var_name(chars: &mut std::iter::Peekable<std::str::Chars>) -> String {
    let mut var_name = String::new();

    while let Some(&c) = chars.peek() {
        if c.is_alphanumeric() || c == '_' {
            var_name.push(chars.next().unwrap());
        } else {
            break;
        }
    }

    var_name
}

fn expand_env_var(var_name: &str, result: &mut String, original: &str) -> PathResult<()> {
    match var_name {
        "HOME" => result.push_str(&home_dir().to_string_lossy()),
        "XDG_CONFIG_HOME" => result.push_str(&xdg_config_home().to_string_lossy()),
        "XDG_DATA_HOME" => result.push_str(&xdg_data_home().to_string_lossy()),
        "XDG_CACHE_HOME" => result.push_str(&xdg_cache_home().to_string_lossy()),
        _ => {
            let value = env::var(var_name).map_err(|_| {
                PathError::MissingEnvVar {
                    input: original.into(),
                    var: var_name.into(),
                }
            })?;
            result.push_str(&value);
        }
    }
    Ok(())
}

#[cfg(test)]
mod tests {
    use std::env;

    use serial_test::serial;

    use super::*;

    #[test]
    fn test_expand_variables_simple() {
        env::set_var("TEST_VAR", "test_value");

        let result = expand_variables("$TEST_VAR/path").unwrap();
        assert_eq!(result, "test_value/path");

        env::remove_var("TEST_VAR");
    }

    #[test]
    fn test_expand_variables_braces() {
        env::set_var("TEST_VAR_BRACES", "test_value");

        let result = expand_variables("${TEST_VAR_BRACES}/path").unwrap();
        assert_eq!(result, "test_value/path");

        env::remove_var("TEST_VAR_BRACES");
    }

    #[test]
    fn test_expand_variables_missing_braces() {
        env::set_var("TEST_VAR_MISSING_BRACES", "test_value");

        let result = expand_variables("${TEST_VAR_MISSING_BRACES");
        assert!(result.is_err());

        env::remove_var("TEST_VAR_MISSING_BRACES");
    }

    #[test]
    fn test_expand_variables_missing_var() {
        let result = expand_variables("$THIS_VAR_DOESNT_EXIST");
        assert!(result.is_err());
    }

    #[test]
    fn test_consume_var_name() {
        let mut chars = "VAR_NAME_123/extra".chars().peekable();
        let var_name = consume_var_name(&mut chars);
        assert_eq!(var_name, "VAR_NAME_123");
    }

    #[test]
    #[serial]
    fn test_xdg_directories() {
        // We need to set HOME to have a predictable home directory for the test
        env::set_var("HOME", "/tmp/home");
        let home = home_dir();
        assert_eq!(home, PathBuf::from("/tmp/home"));

        // Test without XDG variables set
        env::remove_var("XDG_CONFIG_HOME");
        env::remove_var("XDG_DATA_HOME");
        env::remove_var("XDG_CACHE_HOME");

        let config = xdg_config_home();
        let data = xdg_data_home();
        let cache = xdg_cache_home();

        assert_eq!(config, home.join(".config"));
        assert_eq!(data, home.join(".local/share"));
        assert_eq!(cache, home.join(".cache"));
        assert!(config.is_absolute());
        assert!(data.is_absolute());
        assert!(cache.is_absolute());

        // Test with XDG variables set
        env::set_var("XDG_CONFIG_HOME", "/tmp/config");
        env::set_var("XDG_DATA_HOME", "/tmp/data");
        env::set_var("XDG_CACHE_HOME", "/tmp/cache");

        assert_eq!(xdg_config_home(), PathBuf::from("/tmp/config"));
        assert_eq!(xdg_data_home(), PathBuf::from("/tmp/data"));
        assert_eq!(xdg_cache_home(), PathBuf::from("/tmp/cache"));

        env::remove_var("XDG_CONFIG_HOME");
        env::remove_var("XDG_DATA_HOME");
        env::remove_var("XDG_CACHE_HOME");
        env::remove_var("HOME");
    }

    #[test]
    #[serial]
    fn test_resolve_path() {
        env::set_var("HOME", "/tmp/home");

        assert!(resolve_path("").is_err());

        // Absolute path
        assert_eq!(
            resolve_path("/absolute/path").unwrap(),
            PathBuf::from("/absolute/path")
        );

        // Relative path
        let expected_relative = env::current_dir().unwrap().join("relative/path");
        assert_eq!(resolve_path("relative/path").unwrap(), expected_relative);

        // Tilde path
        let home = home_dir();
        assert_eq!(resolve_path("~/path").unwrap(), home.join("path"));
        assert_eq!(resolve_path("~").unwrap(), home);

        // Tilde not at start
        let expected_tilde_middle = env::current_dir().unwrap().join("not/at/~/start");
        assert_eq!(
            resolve_path("not/at/~/start").unwrap(),
            expected_tilde_middle
        );
        env::remove_var("HOME");

        // Unclosed variable
        let result = resolve_path("${VAR");
        assert!(result.is_err());

        // Missing variable
        let result = resolve_path("${VAR}");
        assert!(result.is_err());
    }

    #[test]
    #[serial]
    fn test_home_dir() {
        // Test with HOME set
        env::set_var("HOME", "/tmp/home");
        assert_eq!(home_dir(), PathBuf::from("/tmp/home"));

        // Test with HOME unset
        env::remove_var("HOME");
        let expected = PathBuf::from(format!("/home/{}", get_username()));
        assert_eq!(home_dir(), expected);
    }

    #[test]
    #[serial]
    fn test_expand_variables_edge_cases() {
        env::set_var("HOME", "/tmp/home");

        // Dollar at the end
        assert_eq!(expand_variables("path/$").unwrap(), "path/$");

        // Dollar with invalid char
        assert_eq!(
            expand_variables("path/$!invalid").unwrap(),
            "path/$!invalid"
        );

        // Multiple variables
        env::set_var("VAR1", "val1");
        env::set_var("VAR2", "val2");
        assert_eq!(expand_variables("$VAR1/${VAR2}").unwrap(), "val1/val2");
        env::remove_var("VAR1");
        env::remove_var("VAR2");

        // Tilde expansion
        let home_str = home_dir().to_string_lossy().to_string();
        assert_eq!(
            expand_variables("~/path").unwrap(),
            format!("{}/path", home_str)
        );
        assert_eq!(expand_variables("~").unwrap(), home_str);
        assert_eq!(expand_variables("a/~/b").unwrap(), "a/~/b");
        env::remove_var("HOME");
    }

    #[test]
    #[serial]
    fn test_resolve_path_invalid_cwd() {
        let temp_dir = tempfile::tempdir().unwrap();
        let invalid_path = temp_dir.path().join("invalid");
        std::fs::create_dir(&invalid_path).unwrap();

        let original_cwd = env::current_dir().unwrap();
        env::set_current_dir(&invalid_path).unwrap();
        std::fs::remove_dir(&invalid_path).unwrap();

        let result = resolve_path("relative/path");
        assert!(result.is_err());

        // Restore cwd
        env::set_current_dir(original_cwd).unwrap();
    }

    #[test]
    #[serial]
    fn test_expand_env_var_special_vars() {
        env::set_var("HOME", "/tmp/home");
        env::remove_var("XDG_CONFIG_HOME");
        env::remove_var("XDG_DATA_HOME");
        env::remove_var("XDG_CACHE_HOME");

        let mut result = String::new();
        expand_env_var("HOME", &mut result, "$HOME").unwrap();
        assert_eq!(result, "/tmp/home");

        result.clear();
        expand_env_var("XDG_CONFIG_HOME", &mut result, "$XDG_CONFIG_HOME").unwrap();
        assert_eq!(result, "/tmp/home/.config");

        result.clear();
        expand_env_var("XDG_DATA_HOME", &mut result, "$XDG_DATA_HOME").unwrap();
        assert_eq!(result, "/tmp/home/.local/share");

        result.clear();
        expand_env_var("XDG_CACHE_HOME", &mut result, "$XDG_CACHE_HOME").unwrap();
        assert_eq!(result, "/tmp/home/.cache");

        env::remove_var("HOME");
    }

    #[test]
    #[serial]
    fn test_desktop_dir() {
        // User mode
        env::set_var("XDG_DATA_HOME", "/tmp/data");
        let desktop = desktop_dir(false);
        assert_eq!(desktop, PathBuf::from("/tmp/data/applications"));

        // System mode
        let desktop = desktop_dir(true);
        assert_eq!(desktop, PathBuf::from("/usr/local/share/applications"));
    }

    #[test]
    #[serial]
    fn test_icons_dir() {
        // User mode
        env::set_var("XDG_DATA_HOME", "/tmp/data");
        let icons = icons_dir(false);
        assert_eq!(icons, PathBuf::from("/tmp/data/icons/hicolor"));

        // System mode
        let icons = icons_dir(true);
        assert_eq!(icons, PathBuf::from("/usr/local/share/icons/hicolor"));
    }
}