// font-kit/src/sources/mem.rs
//
// Copyright © 2018 The Pathfinder Project Developers.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

//! A source that keeps fonts in memory.

use crate::error::{FontLoadingError, SelectionError};
use crate::family_handle::FamilyHandle;
use crate::family_name::FamilyName;
use crate::font::Font;
use crate::handle::Handle;
use crate::properties::Properties;
use crate::source::Source;
use std::any::Any;

/// A source that keeps fonts in memory.
#[allow(missing_debug_implementations)]
pub struct MemSource {
    families: Vec<FamilyEntry>,
}

impl MemSource {
    /// Creates a new empty memory source.
    pub fn empty() -> MemSource {
        MemSource { families: vec![] }
    }

    /// Creates a new memory source that contains the given set of font handles.
    ///
    /// The fonts referenced by the handles are eagerly loaded into memory.
    pub fn from_fonts<I>(fonts: I) -> Result<MemSource, FontLoadingError>
    where
        I: Iterator<Item = Handle>,
    {
        let mut families = vec![];
        for handle in fonts {
            add_font(handle, &mut families)?;
        }
        families.sort_by(|a, b| a.family_name.cmp(&b.family_name));
        Ok(MemSource { families })
    }

    /// Add an existing font handle to a `MemSource`.
    ///
    /// Returns the font that was just added.
    ///
    /// Note that adding fonts to an existing `MemSource` is slower than creating a new one from a
    /// `Handle` iterator, since this method sorts after every addition, rather than once at the
    /// end.
    pub fn add_font(&mut self, handle: Handle) -> Result<Font, FontLoadingError> {
        let font = add_font(handle, &mut self.families)?;
        self.families
            .sort_by(|a, b| a.family_name.cmp(&b.family_name));
        Ok(font)
    }

    /// Add a number of existing font handles to a `MemSource`.
    ///
    /// Note that adding fonts to an existing `MemSource` is slower than creating a new one from a
    /// `Handle` iterator, because extra unnecessary sorting with occur with every call to this
    /// method.
    pub fn add_fonts(
        &mut self,
        handles: impl Iterator<Item = Handle>,
    ) -> Result<(), FontLoadingError> {
        for handle in handles {
            add_font(handle, &mut self.families)?;
        }
        self.families
            .sort_by(|a, b| a.family_name.cmp(&b.family_name));
        Ok(())
    }

    /// Returns paths of all fonts installed on the system.
    pub fn all_fonts(&self) -> Result<Vec<Handle>, SelectionError> {
        Ok(self
            .families
            .iter()
            .map(|family| family.font.clone())
            .collect())
    }

    /// Returns the names of all families installed on the system.
    pub fn all_families(&self) -> Result<Vec<String>, SelectionError> {
        let mut families = vec![];
        for family in &self.families {
            if families.last() == Some(&family.family_name) {
                continue;
            }

            families.push(family.family_name.clone());
        }

        Ok(families)
    }

    /// Looks up a font family by name and returns the handles of all the fonts in that family.
    ///
    /// FIXME(pcwalton): Case-insensitive comparison.
    pub fn select_family_by_name(&self, family_name: &str) -> Result<FamilyHandle, SelectionError> {
        let mut first_family_index = self
            .families
            .binary_search_by(|family| (*family.family_name).cmp(family_name))
            .map_err(|_| SelectionError::NotFound)?;

        while first_family_index > 0
            && self.families[first_family_index - 1].family_name == family_name
        {
            first_family_index -= 1
        }
        let mut last_family_index = first_family_index;
        while last_family_index + 1 < self.families.len()
            && self.families[last_family_index + 1].family_name == family_name
        {
            last_family_index += 1
        }

        let families = &self.families[first_family_index..(last_family_index + 1)];
        Ok(FamilyHandle::from_font_handles(
            families.iter().map(|family| family.font.clone()),
        ))
    }

    /// Selects a font by PostScript name, which should be a unique identifier.
    ///
    /// The default implementation, which is used by the DirectWrite and the filesystem backends,
    /// does a brute-force search of installed fonts to find the one that matches.
    pub fn select_by_postscript_name(
        &self,
        postscript_name: &str,
    ) -> Result<Handle, SelectionError> {
        self.families
            .iter()
            .filter(|family_entry| family_entry.postscript_name == postscript_name)
            .map(|family_entry| family_entry.font.clone())
            .next()
            .ok_or(SelectionError::NotFound)
    }

    /// Performs font matching according to the CSS Fonts Level 3 specification and returns the
    /// handle.
    #[inline]
    pub fn select_best_match(
        &self,
        family_names: &[FamilyName],
        properties: &Properties,
    ) -> Result<Handle, SelectionError> {
        <Self as Source>::select_best_match(self, family_names, properties)
    }
}

impl Source for MemSource {
    #[inline]
    fn all_fonts(&self) -> Result<Vec<Handle>, SelectionError> {
        self.all_fonts()
    }

    #[inline]
    fn all_families(&self) -> Result<Vec<String>, SelectionError> {
        self.all_families()
    }

    fn select_family_by_name(&self, family_name: &str) -> Result<FamilyHandle, SelectionError> {
        self.select_family_by_name(family_name)
    }

    fn select_by_postscript_name(&self, postscript_name: &str) -> Result<Handle, SelectionError> {
        self.select_by_postscript_name(postscript_name)
    }

    #[inline]
    fn as_any(&self) -> &dyn Any {
        self
    }

    #[inline]
    fn as_mut_any(&mut self) -> &mut dyn Any {
        self
    }
}

/// Adds a font, but doesn't sort. Returns the font that was created to check for validity.
fn add_font(handle: Handle, families: &mut Vec<FamilyEntry>) -> Result<Font, FontLoadingError> {
    let font = Font::from_handle(&handle)?;
    if let Some(postscript_name) = font.postscript_name() {
        families.push(FamilyEntry {
            family_name: font.family_name(),
            postscript_name,
            font: handle,
        })
    }
    Ok(font)
}

struct FamilyEntry {
    family_name: String,
    postscript_name: String,
    font: Handle,
}