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    /*
     * Copyright (C) 2022  Aravinth Manivannan <realaravinth@batsense.net>
     *
     * This program is free software: you can redistribute it and/or modify
     * it under the terms of the GNU Affero General Public License as
     * published by the Free Software Foundation, either version 3 of the
     * License, or (at your option) any later version.
     *
     * This program is distributed in the hope that it will be useful,
     * but WITHOUT ANY WARRANTY; without even the implied warranty of
     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     * GNU Affero General Public License for more details.
     *
     * You should have received a copy of the GNU Affero General Public License
     * along with this program.  If not, see <https://www.gnu.org/licenses/>.
     */
    use std::path::Path;

    use syntect::highlighting::{Color, ThemeSet};
    use syntect::html::highlighted_html_for_string;
    use syntect::parsing::{SyntaxReference, SyntaxSet};

    pub trait GenerateHTML {
        fn generate(&mut self);
    }

    #[allow(dead_code)]
    pub const STYLE: &str = "
        ";

    thread_local! {
        pub(crate) static SYNTAX_SET: SyntaxSet = SyntaxSet::load_defaults_newlines();
    }

    pub struct SourcegraphQuery<'a> {
        pub filepath: &'a str,
        pub code: &'a str,
    }

    impl<'a> SourcegraphQuery<'a> {
        pub fn syntax_highlight(&self) -> String {
            //    let ss = SYNTAX_SET;
            let ts = ThemeSet::load_defaults();

            let theme = &ts.themes["InspiredGitHub"];
            let c = theme.settings.background.unwrap_or(Color::WHITE);
            let mut num = 1;
            let mut output = format!(
                "<style>
            .gist_file {{
                background-color:#{:02x}{:02x}{:02x};
            }}</style>",
                c.r, c.g, c.b
            );

            // highlighted_html_for_string(&q.code, syntax_set, syntax_def, theme),
            let html = SYNTAX_SET.with(|ss| {
                let language = self.determine_language(ss);
                highlighted_html_for_string(self.code, ss, language, theme)
            });
            let total_lines = html.lines().count();
            for (line_num, line) in html.lines().enumerate() {
                if !line.trim().is_empty() {
                    if line_num == 0 || line_num == total_lines - 1 {
                        output.push_str(line);
                    } else {
                        output.push_str(&format!("<div title='click for more options' id=\"line-{num}\"class=\"line\"><details class='line_links'><summary class='line_top-link'><a href=\"#line-{num}\"<span class=\"line-number\">{num}</span></a>{line}</summary><a href=\"#line-{num}\"<span class=\"line-link\">Permanant link</span></a><a href=\"#line-{num}\"<span class=\"line-link\">Highlight</span></a></details></div>"
                        ));
                        num += 1;
                    }
                }
            }
            output
        }

        // adopted from
        // https://github.com/sourcegraph/sourcegraph/blob/9fe138ae75fd64dce06b621572b252a9c9c8da70/docker-images/syntax-highlighter/crates/sg-syntax/src/lib.rs#L81
        // with minimum modifications. Crate was MIT licensed at the time(2022-03-12 11:11)
        fn determine_language<'b>(&self, syntax_set: &'b SyntaxSet) -> &'b SyntaxReference {
            if self.filepath.is_empty() {
                // Legacy codepath, kept for backwards-compatability with old clients.
                match syntax_set.find_syntax_by_first_line(self.code) {
                    Some(v) => {
                        return v;
                    }
                    None => unimplemented!(), //Err(json!({"error": "invalid extension"})),
                };
            }

            // Split the input path ("foo/myfile.go") into file name
            // ("myfile.go") and extension ("go").
            let path = Path::new(&self.filepath);
            let file_name = path.file_name().and_then(|n| n.to_str()).unwrap_or("");
            let extension = path.extension().and_then(|x| x.to_str()).unwrap_or("");

            // Override syntect's language detection for conflicting file extensions because
            // it's impossible to express this logic in a syntax definition.
            struct Override {
                extension: &'static str,
                prefix_langs: Vec<(&'static str, &'static str)>,
                default: &'static str,
            }
            let overrides = vec![Override {
                extension: "cls",
                prefix_langs: vec![("%", "TeX"), ("\\", "TeX")],
                default: "Apex",
            }];

            if let Some(Override {
                prefix_langs,
                default,
                ..
            }) = overrides.iter().find(|o| o.extension == extension)
            {
                let name = match prefix_langs
                    .iter()
                    .find(|(prefix, _)| self.code.starts_with(prefix))
                {
                    Some((_, lang)) => lang,
                    None => default,
                };
                return syntax_set
                    .find_syntax_by_name(name)
                    .unwrap_or_else(|| syntax_set.find_syntax_plain_text());
            }

            syntax_set
                // First try to find a syntax whose "extension" matches our file
                // name. This is done due to some syntaxes matching an "extension"
                // that is actually a whole file name (e.g. "Dockerfile" or "CMakeLists.txt")
                // see https://github.com/trishume/syntect/pull/170
                .find_syntax_by_extension(file_name)
                .or_else(|| syntax_set.find_syntax_by_extension(extension))
                .or_else(|| syntax_set.find_syntax_by_first_line(self.code))
                .unwrap_or_else(|| syntax_set.find_syntax_plain_text())
        }
    }

    #[cfg(test)]
    mod tests {
        use super::SourcegraphQuery;

        use syntect::parsing::SyntaxSet;

        #[test]
        fn cls_tex() {
            let syntax_set = SyntaxSet::load_defaults_newlines();
            let query = SourcegraphQuery {
                filepath: "foo.cls",
                code: "%",
            };
            let result = query.determine_language(&syntax_set);
            assert_eq!(result.name, "TeX");
            let _result = query.syntax_highlight();
        }

        //#[test]
        //fn cls_apex() {
        //    let syntax_set = SyntaxSet::load_defaults_newlines();
        //    let query = SourcegraphQuery {
        //        filepath: "foo.cls".to_string(),
        //        code: "/**".to_string(),
        //        extension: String::new(),
        //    };
        //    let result = determine_language(&query, &syntax_set);
        //    assert_eq!(result.unwrap().name, "Apex");
        //}
    }