use std::collections::HashSet;

pub fn render_markdown(input: &str) -> String {
    let html = tetratto_shared::markdown::render_markdown_dirty(&parse_text_color(
        &parse_highlight(input),
    ));

    let mut allowed_attributes = HashSet::new();
    allowed_attributes.insert("id");
    allowed_attributes.insert("class");
    allowed_attributes.insert("ref");
    allowed_attributes.insert("aria-label");
    allowed_attributes.insert("lang");
    allowed_attributes.insert("title");
    allowed_attributes.insert("align");
    allowed_attributes.insert("src");
    allowed_attributes.insert("style");

    tetratto_shared::markdown::clean_html(html, allowed_attributes)
}

fn parse_text_color_line(output: &mut String, buffer: &mut String, line: &str) {
    let mut in_color_buffer = false;
    let mut in_main_buffer = false;
    let mut color_buffer = String::new();
    let mut close_1 = false;

    for char in line.chars() {
        if close_1 && char != '%' {
            // we expected to see another percentage to close the main buffer,
            // not getting that means this wasn't meant to be a color
            buffer.push('%');
            in_main_buffer = false;
            close_1 = false;
        }

        match char {
            '%' => {
                if in_color_buffer {
                    in_color_buffer = false;
                    in_main_buffer = true;
                    continue;
                }

                if in_main_buffer {
                    // ending
                    if !close_1 {
                        close_1 = true;
                        continue;
                    }

                    // by this point, we have:   !
                    // %color_buffer%main_buffer%%
                    output.push_str(&format!(
                        "<span style=\"color: {color_buffer}\">{buffer}</span>\n"
                    ));

                    color_buffer.clear();
                    buffer.clear();

                    // ...
                    in_main_buffer = false;
                    close_1 = false;
                    continue;
                }

                // start
                // flush buffer
                output.push_str(&buffer);
                buffer.clear();

                // toggle open
                in_color_buffer = true;
            }
            ' ' => {
                if in_color_buffer == true {
                    buffer.push_str(&color_buffer);
                    color_buffer.clear();
                }

                buffer.push(char);
            }
            _ => {
                if in_color_buffer {
                    color_buffer.push(char)
                } else {
                    buffer.push(char)
                }
            }
        }
    }
}

fn parse_highlight_line(output: &mut String, buffer: &mut String, line: &str) {
    let mut open_1 = false;
    let mut open_2 = false;
    let mut close_1 = false;
    let mut is_open = false;

    for char in line.chars() {
        if close_1 && char != '=' {
            buffer.push('=');
            close_1 = false;
        }

        match char {
            '=' => {
                if !is_open {
                    // flush buffer
                    output.push_str(&buffer);
                    buffer.clear();

                    // toggle open
                    open_1 = true;
                    is_open = true;
                } else {
                    if open_1 {
                        // this is the second open we've recieved
                        open_2 = true;
                        open_1 = false;
                        continue;
                    }

                    if close_1 {
                        // this is the second close we've received
                        output.push_str(&format!("<mark>{buffer}</mark>\n"));
                        buffer.clear();
                        open_1 = false;
                        open_2 = false;
                        close_1 = false;
                        is_open = false;
                        continue;
                    }

                    close_1 = true;
                }
            }
            _ => {
                if open_1 {
                    open_1 = false;
                    buffer.push('=');
                }

                if open_2 && is_open {
                    open_2 = false;
                }

                buffer.push(char);
            }
        }
    }
}

/// Helper macro to quickly allow parsers to ignore fenced code blocks.
macro_rules! parser_ignores_pre {
    ($body:ident, $input:ident) => {{
        let mut in_pre_block = false;
        let mut output = String::new();
        let mut buffer = String::new();

        for line in $input.split("\n") {
            if line.starts_with("```") {
                in_pre_block = !in_pre_block;
                output.push_str(&format!("{line}\n"));
                continue;
            }

            if in_pre_block {
                output.push_str(&format!("{line}\n"));
                continue;
            }

            $body(&mut output, &mut buffer, line);
            output.push_str(&format!("{buffer}\n"));
            buffer.clear();
        }

        output
    }};
}

pub fn parse_text_color(input: &str) -> String {
    parser_ignores_pre!(parse_text_color_line, input)
}

pub fn parse_highlight(input: &str) -> String {
    parser_ignores_pre!(parse_highlight_line, input)
}