// Copyright 2019 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

use {
    anyhow::{format_err, Error},
    char_set::CharSet,
    font_info::{FontAssetSource, FontInfo, FontInfoLoader},
    std::{collections::BTreeSet, path::PathBuf},
};

/// An implementation of [`FakeFontInfoLoader`] that doesn't read the font file, but instead claims
/// that the font file contains exactly the code points that appear in the file name, plus the
/// `index`. For `postscript_name`, it returns the name of the file without the extension.
pub(crate) struct FakeFontInfoLoaderImpl {}

impl FakeFontInfoLoaderImpl {
    pub fn new() -> Self {
        FakeFontInfoLoaderImpl {}
    }
}

impl FontInfoLoader for FakeFontInfoLoaderImpl {
    fn load_font_info<S, E>(&self, source: S, index: u32) -> Result<FontInfo, Error>
    where
        S: TryInto<FontAssetSource, Error = E>,
        E: Sync + Send + Into<Error>,
    {
        let source: FontAssetSource = source.try_into().map_err(|e| e.into())?;
        let path = match source {
            FontAssetSource::Stream(_) => {
                return Err(format_err!("FakeFontInfoLoaderImpl only supports file paths"));
            }
            FontAssetSource::FilePath(path) => PathBuf::from(path),
        };

        let file_name = path
            .file_name()
            .and_then(|x| x.to_str())
            .ok_or_else(|| format_err!("Couldn't get file name from {:?}", path))?;
        let mut chars: BTreeSet<u32> = file_name.chars().map(|c| c as u32).collect();
        chars.insert(index);
        let chars: Vec<u32> = chars.into_iter().collect();

        let char_set = CharSet::new(chars);
        let mut postscript_name =
            file_name.split('.').next().unwrap_or("Postscript-Name").to_string();
        // Postscript names must be unique
        if index > 0 {
            postscript_name.push_str(format!("-{}", index).as_str());
        }
        let full_name = postscript_name.replace("-", " ");

        Ok(FontInfo {
            char_set,
            postscript_name: Some(postscript_name),
            full_name: Some(full_name),
        })
    }
}

#[cfg(test)]
mod tests {
    use {super::*, char_collection::char_collect, pretty_assertions::assert_eq};

    #[test]
    fn test_load_font_info() -> Result<(), Error> {
        let loader = FakeFontInfoLoaderImpl::new();
        let source = FontAssetSource::FilePath(
            "DIRECTORY/abcdefghijklmnopqrstuvwxyz-0123456789.ttf".to_string(),
        );

        let actual = loader.load_font_info(source, 0x999)?;
        let expected = FontInfo {
            char_set: char_collect!('a'..='z', '0'..='9', '-', '.', '\u{999}').into(),
            postscript_name: Some("abcdefghijklmnopqrstuvwxyz-0123456789-2457".to_string()),
            full_name: Some("abcdefghijklmnopqrstuvwxyz 0123456789 2457".to_string()),
        };

        assert_eq!(actual, expected);
        Ok(())
    }
}