//! # freedesktop-icons
//!
//! This crate provides a [freedesktop icon](https://specifications.freedesktop.org/icon-theme-spec/icon-theme-spec-latest.html#implementation_notes) lookup implementation.
//!
//! It exposes a single lookup function to find icons based on their `name`, `theme`, `size` and `scale`.
//!
//! ## Example
//!
//! **Simple lookup:**
//!
//! The following snippet get an icon from the default 'hicolor' theme
//! with the default scale (`1`) and the default size (`24`).
//!
//! ```rust
//! # fn main() {
//! use cosmic_freedesktop_icons::lookup;
//!
//! let icon = lookup("firefox").find();
//! # }
//!```
//!
//! **Complex lookup:**
//!
//! If you have specific requirements for your lookup you can use the provided builder functions:
//!
//! ```rust
//! # fn main() {
//! use cosmic_freedesktop_icons::lookup;
//!
//! let icon = lookup("firefox")
//!     .with_size(48)
//!     .with_scale(2)
//!     .with_theme("Arc")
//!     .find();
//! # }
//!```
//! **Cache:**
//!
//! If your application is going to repeat the same icon lookups multiple times
//! you can use the internal cache to improve performance.
//!
//! ```rust
//! # fn main() {
//! use cosmic_freedesktop_icons::lookup;
//!
//! let icon = lookup("firefox")
//!     .with_size(48)
//!     .with_scale(2)
//!     .with_theme("Arc")
//!     .with_cache()
//!     .find();
//! # }
//! ```
use theme::BASE_PATHS;

use crate::cache::{CACHE, CacheEntry};
use crate::theme::{THEMES, Theme, try_build_icon_path};
use std::collections::HashSet;
use std::hash::{Hash, Hasher};
use std::io::BufRead;
use std::path::PathBuf;
use std::time::Instant;

mod cache;
mod theme;

/// Return the list of installed themes on the system
///
/// ## Example
/// ```rust,no_run
/// # fn main() {
/// use cosmic_freedesktop_icons::list_themes;
///
/// let themes: Vec<String> = list_themes();
///
/// assert_eq!(themes, vec![
///     "Adwaita", "Arc", "Breeze Light", "HighContrast", "Papirus", "Papirus-Dark",
///     "Papirus-Light", "Breeze", "Breeze Dark", "Breeze", "ePapirus", "ePapirus-Dark", "Hicolor"
/// ])
/// # }
pub fn list_themes() -> Vec<String> {
    let mut themes = THEMES
        .values()
        .flatten()
        .map(|path| &path.index)
        .filter_map(|index| {
            let file = std::fs::File::open(index).ok()?;
            let mut reader = std::io::BufReader::new(file);

            let mut line = String::new();
            while let Ok(read) = reader.read_line(&mut line) {
                if read == 0 {
                    break;
                }

                if let Some(name) = line.strip_prefix("Name=") {
                    return Some(name.trim().to_owned());
                }

                line.clear();
            }

            None
        })
        .collect::<Vec<_>>();
    themes.dedup();
    themes
}

/// Return the default GTK theme if set.
///
/// ## Example
/// ```rust, no_run
/// use cosmic_freedesktop_icons::default_theme_gtk;
///
/// let theme = default_theme_gtk();
///
/// assert_eq!(Some("Adwaita"), theme.as_deref());
/// ```
pub fn default_theme_gtk() -> Option<String> {
    // Calling gsettings is the simplest way to retrieve the default icon theme without adding
    // GTK as a dependency. There seems to be several ways to set the default GTK theme
    // including a file in XDG_CONFIG_HOME as well as an env var. Gsettings is the most
    // straightforward method.
    let gsettings = std::process::Command::new("gsettings")
        .args(["get", "org.gnome.desktop.interface", "icon-theme"])
        .output()
        .ok()?;

    // Only return the theme if it's in the cache.
    if gsettings.status.success() {
        let name = String::from_utf8(gsettings.stdout).ok()?;
        let name = name.trim().trim_matches('\'');
        THEMES.get(name).and_then(|themes| {
            themes.first().and_then(|path| {
                let file = std::fs::File::open(&path.index).ok()?;
                let mut reader = std::io::BufReader::new(file);

                let mut line = String::new();
                while let Ok(read) = reader.read_line(&mut line) {
                    if read == 0 {
                        break;
                    }

                    if let Some(name) = line.strip_prefix("Name=") {
                        return Some(name.trim().to_owned());
                    }

                    line.clear();
                }

                None
            })
        })
    } else {
        None
    }
}

/// The lookup builder struct, holding all the lookup query parameters.
pub struct LookupBuilder<'a> {
    name: &'a str,
    cache: bool,
    force_svg: bool,
    scale: u16,
    size: u16,
    theme: &'a str,
}

/// Build an icon lookup for the given icon name.
///
/// ## Example
/// ```rust
/// # fn main() {
/// use cosmic_freedesktop_icons::lookup;
///
/// let icon = lookup("firefox").find();
/// # }
pub fn lookup(name: &str) -> LookupBuilder<'_> {
    LookupBuilder::new(name)
}

impl<'a> LookupBuilder<'a> {
    /// Restrict the lookup to the given icon size.
    ///
    /// ## Example
    /// ```rust
    /// # fn main() {
    /// use cosmic_freedesktop_icons::lookup;
    ///
    /// let icon = lookup("firefox")
    ///     .with_size(48)
    ///     .find();
    /// # }
    #[inline]
    pub fn with_size(mut self, size: u16) -> Self {
        self.size = size;
        self
    }

    /// Restrict the lookup to the given scale.
    ///
    /// ## Example
    /// ```rust
    /// # fn main() {
    /// use cosmic_freedesktop_icons::lookup;
    ///
    /// let icon = lookup("firefox")
    ///     .with_scale(2)
    ///     .find();
    /// # }
    #[inline]
    pub fn with_scale(mut self, scale: u16) -> Self {
        self.scale = scale;
        self
    }

    /// Add the given theme to the current lookup :
    /// ## Example
    /// ```rust
    /// # fn main() {
    /// use cosmic_freedesktop_icons::lookup;
    ///
    /// let icon = lookup("firefox")
    ///     .with_theme("Papirus")
    ///     .find();
    /// # }
    #[inline]
    pub fn with_theme<'b: 'a>(mut self, theme: &'b str) -> Self {
        self.theme = theme;
        self
    }

    /// Store the result of the lookup in cache, subsequent
    /// lookup will first try to get the cached icon.
    /// This can drastically increase lookup performances for application
    /// that repeat the same lookups, an application launcher for instance.
    ///
    /// ## Example
    /// ```rust
    /// # fn main() {
    /// use cosmic_freedesktop_icons::lookup;
    ///
    /// let icon = lookup("firefox")
    ///     .with_scale(2)
    ///     .with_cache()
    ///     .find();
    /// # }
    #[inline]
    pub fn with_cache(mut self) -> Self {
        self.cache = true;
        self
    }

    /// By default [`find`] will prioritize Png over Svg icon.
    /// Use this if you need to prioritize Svg icons. This could be useful
    /// if you need a modifiable icon, to match a user theme for instance.
    ///
    /// ## Example
    /// ```rust
    /// # fn main() {
    /// use cosmic_freedesktop_icons::lookup;
    ///
    /// let icon = lookup("firefox")
    ///     .force_svg()
    ///     .find();
    /// # }
    #[inline]
    pub fn force_svg(mut self) -> Self {
        self.force_svg = true;
        self
    }

    /// Execute the current lookup
    /// if no icon is found in the current theme fallback to
    /// `/usr/share/icons/hicolor` theme and then to `/usr/share/pixmaps`.
    #[inline]
    pub fn find(self) -> Option<PathBuf> {
        if self.name.is_empty() {
            return None;
        }

        // Lookup for an icon in the given theme and fallback to 'hicolor' default theme
        self.lookup_in_theme()
    }

    fn new<'b: 'a>(name: &'b str) -> Self {
        Self {
            name,
            cache: false,
            force_svg: false,
            scale: 1,
            size: 24,
            theme: "hicolor",
        }
    }

    // Recursively lookup for icon in the given theme and its parents
    fn lookup_in_theme(&self) -> Option<PathBuf> {
        // If cache is activated, attempt to get the icon there first
        // If the icon was previously search but not found, we return
        // `None` early, otherwise, attempt to perform a lookup
        if self.cache {
            match self.cache_lookup(self.theme) {
                CacheEntry::Found(icon) => return Some(icon),
                CacheEntry::NotFound(last_check)
                    if last_check.duration_since(Instant::now()).as_secs() < 5 =>
                {
                    return None;
                }
                _ => (),
            }
        }

        // Records theme paths that have already been searched.
        let searched_themes = &mut HashSet::new();
        // Record themes whose inherits have been searched.
        let search_inherits = &mut HashSet::new();

        // Then lookup in the given theme
        THEMES
            .get(self.theme)
            .or_else(|| THEMES.get("hicolor"))
            .and_then(|icon_themes| {
                let icon = icon_themes
                    .iter()
                    // Search the active icon themes
                    .find_map(|theme| self.search_theme(searched_themes, theme))
                    // Search the inherits of those icon themes.
                    .or_else(|| {
                        icon_themes.iter().find_map(|t| {
                            self.search_theme_inherits(search_inherits, searched_themes, t)
                        })
                    })
                    // Search the hicolor icon theme if it was not previously searched
                    .or_else(|| self.search_inherited_theme(searched_themes, "hicolor"))
                    .or_else(|| {
                        for theme_base_dir in BASE_PATHS.iter() {
                            if let Some(icon) =
                                try_build_icon_path(self.name, theme_base_dir, self.force_svg)
                            {
                                return Some(icon);
                            }
                        }
                        None
                    })
                    .or_else(|| {
                        let p = PathBuf::from(&self.name);
                        if let (Some(name), Some(parent)) = (p.file_stem(), p.parent()) {
                            try_build_icon_path(&name.to_string_lossy(), parent, self.force_svg)
                        } else {
                            None
                        }
                    });

                if self.cache {
                    self.store(self.theme, icon)
                } else {
                    icon
                }
            })
    }

    #[inline]
    pub fn cache_clear(&mut self) {
        CACHE.clear();
    }

    #[inline]
    pub fn cache_reset_none(&mut self) {
        CACHE.reset_none();
    }

    #[inline]
    fn cache_lookup(&self, theme: &str) -> CacheEntry {
        CACHE.get(theme, self.size, self.scale, self.name)
    }

    #[inline]
    fn store(&self, theme: &str, icon: Option<PathBuf>) -> Option<PathBuf> {
        CACHE.insert(theme, self.size, self.scale, self.name, &icon);
        icon
    }

    /// Search a theme by its path for a matching icon if not already searched.
    fn search_theme(&self, searched_themes: &mut HashSet<u64>, theme: &Theme) -> Option<PathBuf> {
        // Store hash of the theme.
        let theme_hash = {
            let mut hasher = std::hash::DefaultHasher::new();
            theme.path.0.hash(&mut hasher);
            hasher.finish()
        };

        if searched_themes.insert(theme_hash) {
            return theme.try_get_icon(self.name, self.size, self.scale, self.force_svg);
        }

        None
    }

    // Search the inherits of a theme if not already searched.
    fn search_theme_inherits(
        &self,
        search_inherits: &mut HashSet<u64>,
        searched_themes: &mut HashSet<u64>,
        theme: &Theme,
    ) -> Option<PathBuf> {
        // Store hash of the theme.
        let theme_hash = {
            let mut hasher = std::hash::DefaultHasher::new();
            theme.path.0.hash(&mut hasher);
            hasher.finish()
        };

        if search_inherits.insert(theme_hash) {
            let Ok(file) = theme::read_ini_theme(&theme.index) else {
                return None;
            };

            let Ok(file) = std::str::from_utf8(file.as_ref()) else {
                return None;
            };

            // Search all inherited themes that we haven't already searched
            return theme
                .inherits(file)
                .into_iter()
                .find_map(|parent| self.search_inherited_theme(searched_themes, parent));
        }

        None
    }

    /// Search the inherits of a theme by its name if not already searched.
    fn search_inherited_theme(
        &self,
        searched_themes: &mut HashSet<u64>,
        theme: &str,
    ) -> Option<PathBuf> {
        THEMES
            .get(theme)?
            .iter()
            .find_map(|t| self.search_theme(searched_themes, t))
    }
}

// WARNING: these test are highly dependent on your installed icon-themes.
// If you want to run them, make sure you have 'Papirus' and 'Arc' icon-themes installed.
#[cfg(test)]
mod test {
    use crate::{CACHE, CacheEntry, lookup};
    use speculoos::prelude::*;
    use std::path::PathBuf;

    #[test]
    fn hicolor_firefox_24_png() {
        let firefox = lookup("firefox").find();

        asserting!("Firefox contains only a 16x16 and 32x32 icon, so 16x16 should be returned")
            .that(&firefox)
            .is_some()
            .is_equal_to(PathBuf::from(
                "/usr/share/icons/hicolor/16x16/apps/firefox.png",
            ));
    }

    #[test]
    fn hicolor_firefox_48_png() {
        let firefox = lookup("firefox").with_size(48).find();

        asserting!("Firefox has a 48x48 icon, so that should be returned")
            .that(&firefox)
            .is_some()
            .is_equal_to(PathBuf::from(
                "/usr/share/icons/hicolor/48x48/apps/firefox.png",
            ));
    }

    #[test]
    fn hicolor_firefox_svg_fallback_to_png() {
        let firefox = lookup("firefox").force_svg().find();

        asserting!("Lookup with no parameters should return an existing icon")
            .that(&firefox)
            .is_some()
            .is_equal_to(PathBuf::from(
                "/usr/share/icons/hicolor/16x16/apps/firefox.png",
            ));
    }

    #[test]
    fn cosmic_weather_storm_symbolic() {
        let firefox = lookup("weather-storm-symbolic").with_theme("Cosmic").find();

        asserting!("Is the cosmic icon theme installed?")
            .that(&firefox)
            .is_some()
            .is_equal_to(PathBuf::from(
                "/usr/share/icons/Cosmic/scalable/status/weather-storm-symbolic.svg",
            ));
    }

    #[test]
    fn cosmic_weather_storm_symbolic_force_svg() {
        let firefox = lookup("weather-storm-symbolic")
            .with_theme("Cosmic")
            .force_svg()
            .find();

        asserting!("Is the cosmic icon theme installed?")
            .that(&firefox)
            .is_some()
            .is_equal_to(PathBuf::from(
                "/usr/share/icons/Cosmic/scalable/status/weather-storm-symbolic.svg",
            ));
    }

    #[test]
    #[cfg(feature = "local_tests")]
    fn theme_lookup() {
        let firefox = lookup("firefox").with_theme("Papirus").find();

        asserting!("Lookup with no parameters should return an existing icon")
            .that(&firefox)
            .is_some()
            .is_equal_to(PathBuf::from(
                "/usr/share/icons/Papirus/24x24/apps/firefox.svg",
            ));
    }

    #[test]
    #[cfg(feature = "local_tests")]
    fn should_fallback_to_parent_theme() {
        let icon = lookup("video-single-display-symbolic")
            .with_theme("Arc")
            .find();

        asserting!("Lookup for an icon in the Arc theme should find the icon in its parent")
            .that(&icon)
            .is_some()
            .is_equal_to(PathBuf::from(
                "/usr/share/icons/Adwaita/symbolic/devices/video-single-display-symbolic.svg",
            ));
    }

    #[test]
    #[cfg(feature = "local_tests")]
    fn should_fallback_to_pixmaps_utlimately() {
        let archlinux_logo = lookup("archlinux-logo")
            .with_size(16)
            .with_scale(1)
            .with_theme("Papirus")
            .find();

        asserting!("When lookup fail in theme, icon should be found in '/usr/share/pixmaps'")
            .that(&archlinux_logo)
            .is_some()
            .is_equal_to(PathBuf::from("/usr/share/pixmaps/archlinux-logo.png"));
    }

    #[test]
    #[cfg(feature = "local_tests")]
    fn compare_to_linincon_with_theme() {
        let lin_wireshark = linicon::lookup_icon("wireshark")
            .next()
            .unwrap()
            .unwrap()
            .path;

        let wireshark = lookup("wireshark")
            .with_size(16)
            .with_scale(1)
            .with_theme("Papirus")
            .find();

        asserting!("Given the same input parameter, lookup should output be the same as linincon")
            .that(&wireshark)
            .is_some()
            .is_equal_to(lin_wireshark);
    }

    #[test]
    fn should_not_attempt_to_lookup_a_not_found_cached_icon() {
        let not_found = lookup("not-found").with_cache().find();

        assert_that!(not_found).is_none();

        let expected_cache_result = CACHE.get("hicolor", 24, 1, "not-found");

        assert!(
            matches!(expected_cache_result, CacheEntry::NotFound(..)),
            "When lookup fails a first time, subsequent attempts should fail from cache"
        );
    }
}