// font-kit/src/sources/fontconfig.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 contains the fonts installed on the system, as reported by the Fontconfig
//! library.
//!
//! On macOS and Windows, the Cargo feature `source-fontconfig` can be used to opt into fontconfig
//! support. To prefer it over the native font source (only if you know what you're doing), use the
//! `source-fontconfig-default` feature.

use fontconfig::fontconfig::{FcBool, FcConfig, FcFontList, FcInitLoadConfigAndFonts, FcObjectSet};
use fontconfig::fontconfig::{FcObjectSetAdd, FcObjectSetCreate, FcObjectSetDestroy, FcPattern};
use fontconfig::fontconfig::{FcPatternAddString, FcPatternCreate, FcPatternDestroy};
use fontconfig::fontconfig::{FcPatternGetInteger, FcPatternGetString, FcResultMatch};
use std::ffi::{CStr, CString};
use std::os::raw::{c_char, c_uchar};
use std::path::PathBuf;
use std::ptr;
use std::slice;

use error::SelectionError;
use family_handle::FamilyHandle;
use family_name::FamilyName;
use handle::Handle;
use properties::Properties;
use source::Source;

#[allow(dead_code, non_upper_case_globals)]
const FcFalse: FcBool = 0;
#[allow(non_upper_case_globals)]
const FcTrue: FcBool = 1;

const FC_FAMILY: &'static [u8] = b"family\0";
const FC_FILE: &'static [u8] = b"file\0";
const FC_INDEX: &'static [u8] = b"index\0";
const FC_POSTSCRIPT_NAME: &'static [u8] = b"postscriptname\0";

/// A source that contains the fonts installed on the system, as reported by the Fontconfig
/// library.
///
/// On macOS and Windows, the Cargo feature `source-fontconfig` can be used to opt into fontconfig
/// support. To prefer it over the native font source (only if you know what you're doing), use the
/// `source-fontconfig-default` feature.
pub struct FontconfigSource {
    fontconfig: *mut FcConfig,
}

impl FontconfigSource {
    /// Initializes Fontconfig and prepares it for queries.
    pub fn new() -> FontconfigSource {
        unsafe {
            FontconfigSource {
                fontconfig: FcInitLoadConfigAndFonts(),
            }
        }
    }

    /// Returns the names of all families installed on the system.
    pub fn all_families(&self) -> Result<Vec<String>, SelectionError> {
        unsafe {
            let pattern = FcPatternObject::new();

            // We want the file path and the font index.
            let mut object_set = FcObjectSetObject::new();
            object_set.push_string(FC_FAMILY);

            let font_set = FcFontList(self.fontconfig, pattern.pattern, object_set.object_set);
            if font_set.is_null() {
                return Err(SelectionError::NotFound)
            }

            let font_patterns = slice::from_raw_parts((*font_set).fonts,
                                                      (*font_set).nfont as usize);

            let mut result_families = vec![];
            for font_pattern in font_patterns {
                let family = match fc_pattern_get_string(*font_pattern, FC_FAMILY) {
                    None => continue,
                    Some(family) => family,
                };
                result_families.push(family);
            }

            result_families.sort();
            result_families.dedup();

            if !result_families.is_empty() {
                Ok(result_families)
            } else {
                Err(SelectionError::NotFound)
            }
        }
    }

    /// Looks up a font family by name and returns the handles of all the fonts in that family.
    pub fn select_family_by_name(&self, family_name: &str)
                                 -> Result<FamilyHandle, SelectionError> {
        unsafe {
            let mut pattern = FcPatternObject::new();
            pattern.push_string(FC_FAMILY, family_name.to_owned());

            // We want the file path and the font index.
            let mut object_set = FcObjectSetObject::new();
            object_set.push_string(FC_FILE);
            object_set.push_string(FC_INDEX);

            let font_set = FcFontList(self.fontconfig, pattern.pattern, object_set.object_set);
            assert!(!font_set.is_null());

            let font_patterns = slice::from_raw_parts((*font_set).fonts,
                                                      (*font_set).nfont as usize);

            let mut result_fonts = vec![];
            for font_pattern in font_patterns {
                result_fonts.push(self.create_font_handle_from_fontconfig_pattern(*font_pattern))
            }

            if !result_fonts.is_empty() {
                Ok(FamilyHandle::from_font_handles(result_fonts.into_iter()))
            } else {
                Err(SelectionError::NotFound)
            }
        }
    }

    /// 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> {
        unsafe {
            let mut pattern = FcPatternObject::new();
            pattern.push_string(FC_POSTSCRIPT_NAME, postscript_name.to_owned());

            // We want the file path and the font index.
            let mut object_set = FcObjectSetObject::new();
            object_set.push_string(FC_FILE);
            object_set.push_string(FC_INDEX);

            let font_set = FcFontList(self.fontconfig, pattern.pattern, object_set.object_set);
            assert!(!font_set.is_null());

            let font_patterns = slice::from_raw_parts((*font_set).fonts,
                                                      (*font_set).nfont as usize);
            if !font_patterns.is_empty() {
                Ok(self.create_font_handle_from_fontconfig_pattern(font_patterns[0]))
            } else {
                Err(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)
    }

    unsafe fn create_font_handle_from_fontconfig_pattern(&self, font_pattern: *mut FcPattern)
                                                         -> Handle {
        let font_path = fc_pattern_get_string(font_pattern, FC_FILE).unwrap();
        let font_index = fc_pattern_get_integer(font_pattern, FC_INDEX).unwrap() as u32;
        Handle::from_path(PathBuf::from(font_path), font_index)
    }
}

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

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

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

struct FcPatternObject {
    pattern: *mut FcPattern,
    c_strings: Vec<CString>,
}

impl Drop for FcPatternObject {
    #[inline]
    fn drop(&mut self) {
        unsafe {
            FcPatternDestroy(self.pattern)
        }
    }
}

impl FcPatternObject {
    fn new() -> FcPatternObject {
        unsafe {
            FcPatternObject {
                pattern: FcPatternCreate(),
                c_strings: vec![],
            }
        }
    }

    unsafe fn push_string(&mut self, object: &'static [u8], value: String) {
        let c_string = CString::new(value).unwrap();
        FcPatternAddString(self.pattern,
                           object.as_ptr() as *const c_char,
                           c_string.as_ptr() as *const c_uchar);
        self.c_strings.push(c_string)
    }
}

struct FcObjectSetObject {
    object_set: *mut FcObjectSet,
}

impl Drop for FcObjectSetObject {
    fn drop(&mut self) {
        unsafe {
            FcObjectSetDestroy(self.object_set)
        }
    }
}

impl FcObjectSetObject {
    fn new() -> FcObjectSetObject {
        unsafe {
            FcObjectSetObject {
                object_set: FcObjectSetCreate(),
            }
        }
    }

    unsafe fn push_string(&mut self, object: &'static [u8]) {
        assert_eq!(FcObjectSetAdd(self.object_set, object.as_ptr() as *const c_char), FcTrue);
    }
}

unsafe fn fc_pattern_get_string(pattern: *mut FcPattern, object: &'static [u8]) -> Option<String> {
    let mut string = ptr::null_mut();
    if FcPatternGetString(pattern,
                          object.as_ptr() as *const c_char,
                          0,
                          &mut string) != FcResultMatch {
        return None
    }
    if string.is_null() {
        return None
    }
    CStr::from_ptr(string as *const c_char).to_str().ok().map(|string| string.to_owned())
}

unsafe fn fc_pattern_get_integer(pattern: *mut FcPattern, object: &'static [u8]) -> Option<i32> {
    let mut integer = 0;
    if FcPatternGetInteger(pattern,
                           object.as_ptr() as *const c_char,
                           0,
                           &mut integer) != FcResultMatch {
        return None
    }
    Some(integer)
}