use std::{
    io::{stdout, BufWriter, Write},
    path::PathBuf,
    str::FromStr,
};

use syntect::{
    dumps::{dump_to_uncompressed_file, from_uncompressed_dump_file},
    highlighting::{Color, FontStyle, ScopeSelectors, ThemeSet},
    parsing::{ParseState, ScopeStack, SyntaxSet, SyntaxSetBuilder},
};

fn main() {
    match std::env::var("CGIT_SYNTECT_MODE").as_deref().ok() {
        Some("compile") => compile(),
        Some("theme") => theme(),
        None | Some("") | Some("highlight") => highlight(),
        _ => panic!("unknown mode"),
    }
}

fn compile() {
    let mut args = std::env::args();
    args.next(); // arg0
    let input: PathBuf = args.next().unwrap().into();
    let output: PathBuf = args.next().unwrap().into();
    let mut builder = SyntaxSetBuilder::new();
    builder.add_plain_text_syntax();
    builder.add_from_folder(input, true).unwrap();
    let set = builder.build();
    dump_to_uncompressed_file(&set, output).unwrap();
}

fn theme() {
    let mut args = std::env::args();
    args.next(); // arg0
    let input: PathBuf = args.next().unwrap().into();
    let css_path: PathBuf = args.next().unwrap().into();
    let scopes_path: PathBuf = args.next().unwrap().into();

    let theme = ThemeSet::get_theme(input).unwrap();
    let mut css_gen = Vec::new();
    let mut scopes_gen = Vec::new();

    let mut global_css = String::new();
    global_css.push_str(".highlight {\n");
    if let Some(bg) = theme.settings.background {
        global_css.push_str("  background-color: #");
        global_css.extend(hex_color(bg));
        global_css.push_str(";\n");
    }
    global_css.push_str("}\n");
    css_gen.push(global_css);

    for (idx, item) in theme.scopes.into_iter().enumerate() {
        let selectors_str = selectors_to_string(item.scope);

        let mut css = String::new();

        css.push_str(&format!("/* {selectors_str} */\n"));
        css.push_str(&format!(".hl-style{idx} {{\n"));

        if let Some(fg) = item.style.foreground {
            css.push_str("  color: #");
            css.extend(hex_color(fg));
            css.push_str(";\n");
        }

        if let Some(bg) = item.style.background {
            css.push_str("  background-color: #");
            css.extend(hex_color(bg));
            css.push_str(";\n");
        }

        if let Some(font) = item.style.font_style {
            if font.contains(FontStyle::BOLD) {
                css.push_str("  font-weight: bold;\n");
            }
            if font.contains(FontStyle::UNDERLINE) {
                css.push_str("  text-decoration: underline;\n");
            }
            if font.contains(FontStyle::ITALIC) {
                css.push_str("  font-style: italic;\n");
            }
        }

        css.push_str("}\n");
        css_gen.push(css);

        scopes_gen.push(selectors_str);
    }

    std::fs::write(css_path, css_gen.join("\n")).unwrap();
    std::fs::write(scopes_path, scopes_gen.join("\n")).unwrap();
}

fn selectors_to_string(selectors: ScopeSelectors) -> String {
    let mut scopes = Vec::new();
    for scope in selectors.selectors {
        let mut ser = String::new();
        ser.push_str(scope.path.to_string().trim());
        for exc in scope.excludes {
            ser.push_str(" -");
            ser.push_str(exc.to_string().trim());
        }
        scopes.push(ser);
    }
    scopes.join(", ")
}

fn hex_color(color: Color) -> [char; 8] {
    const HEX_DIGIT_LOOKUP: &[u8; 16] = b"0123456789abcdef";
    [
        HEX_DIGIT_LOOKUP[(color.r >> 4) as usize] as char,
        HEX_DIGIT_LOOKUP[(color.r & 0xf) as usize] as char,
        HEX_DIGIT_LOOKUP[(color.g >> 4) as usize] as char,
        HEX_DIGIT_LOOKUP[(color.g & 0xf) as usize] as char,
        HEX_DIGIT_LOOKUP[(color.b >> 4) as usize] as char,
        HEX_DIGIT_LOOKUP[(color.b & 0xf) as usize] as char,
        HEX_DIGIT_LOOKUP[(color.a >> 4) as usize] as char,
        HEX_DIGIT_LOOKUP[(color.a & 0xf) as usize] as char,
    ]
}

fn highlight() {
    let mut args = std::env::args();
    args.next(); // arg0
    let highlight_file: PathBuf = args.next().unwrap().into();

    let syntax_dump = std::env::var("CGIT_SYNTECT_SYNTAXES")
        .map(PathBuf::from)
        .unwrap_or_else(|_| PathBuf::from("/usr/share/cgit-syntect/syntax.packdump"));
    let set: SyntaxSet = from_uncompressed_dump_file(syntax_dump).unwrap();

    let scope_dump = std::env::var("CGIT_SYNTECT_SCOPES")
        .map(PathBuf::from)
        .unwrap_or_else(|_| PathBuf::from("/usr/share/cgit-syntect/scopes"));
    let scopes = std::fs::read_to_string(scope_dump)
        .unwrap()
        .lines()
        .map(ScopeSelectors::from_str)
        .map(|sels| sels.unwrap())
        .collect::<Vec<_>>();

    let mut line = String::new();
    std::io::stdin().read_line(&mut line).unwrap();
    if !line.ends_with('\n') {
        line.push('\n');
    }

    let file_name = highlight_file
        .file_name()
        .and_then(|n| n.to_str())
        .unwrap_or("");
    let extension = highlight_file
        .extension()
        .and_then(|x| x.to_str())
        .unwrap_or("");
    let syntax = set
        .find_syntax_by_extension(file_name)
        .or_else(|| set.find_syntax_by_extension(extension))
        .or_else(|| set.find_syntax_by_first_line(&line))
        .unwrap_or_else(|| set.find_syntax_plain_text());

    let mut stdout = BufWriter::new(stdout().lock());

    write!(&mut stdout, r#"<pre class="highlight"><code>"#).unwrap();

    let mut parse = ParseState::new(syntax);
    let mut stack = ScopeStack::new();
    loop {
        let mut cursor = 0;
        let ops = parse.parse_line(&line, &set).unwrap();
        let mut spans = Vec::new();

        for (at, op) in ops {
            if at != cursor {
                let mut max_power = f64::NEG_INFINITY;
                let mut selected = None;
                for (idx, scope) in scopes.iter().enumerate() {
                    if let Some(power) = scope.does_match(stack.as_slice()) {
                        if power.0 > max_power {
                            max_power = power.0;
                            selected = Some(idx);
                        }
                    }
                }
                spans.push((&line[cursor..at], selected));
            }
            stack.apply(&op).unwrap();
            cursor = at;
        }

        if line.len() != cursor {
            spans.push((&line[cursor..], None));
        }

        for (section, class) in spans {
            if let Some(idx) = class {
                write!(&mut stdout, r#"<span class="hl-style{idx}">"#).unwrap();
            }
            for ch in section.chars() {
                match ch {
                    '>' => write!(&mut stdout, "&gt;").unwrap(),
                    '<' => write!(&mut stdout, "&lt;").unwrap(),
                    '&' => write!(&mut stdout, "&amp;").unwrap(),
                    '\'' => write!(&mut stdout, "&#39;").unwrap(),
                    '"' => write!(&mut stdout, "&quot;").unwrap(),
                    _ => write!(&mut stdout, "{ch}").unwrap(),
                }
            }
            if class.is_some() {
                write!(&mut stdout, "</span>").unwrap();
            }
        }

        stdout.flush().unwrap();
        line.clear();
        if std::io::stdin().read_line(&mut line).unwrap() == 0 {
            write!(&mut stdout, "\n").unwrap();
            break;
        }
        if !line.ends_with('\n') {
            line.push('\n');
        }
    }

    write!(&mut stdout, "</code></pre>").unwrap();
}