use std::collections::HashSet;

pub fn render_markdown(input: &str) -> String {
    let html = tetratto_shared::markdown::render_markdown_dirty(&parse_text_color(
        &parse_highlight(&parse_link(&parse_image(&parse_image_size(
            &parse_underline(&parse_comment(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.replace("<style>", "<span>:temp_style")
            .replace("</style>", "</span>:temp_style"),
        allowed_attributes,
    )
    .replace("<span>:temp_style", "<style>")
    .replace("</span>:temp_style", "</style>")
}

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);
            }
        }
    }
}

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

    for char in line.chars() {
        if open_1 && char != '~' {
            is_open = false;
            open_1 = false;
            buffer.push('!');
        }

        if close_1 && char != '!' {
            is_open = false;
            close_1 = false;
            buffer.push('~');
        }

        match char {
            '~' => {
                if open_1 {
                    open_1 = false;
                    is_open = true;
                } else if is_open {
                    // open close
                    close_1 = true;
                }
            }
            '!' => {
                if close_1 {
                    // close
                    let mut s: Vec<&str> = buffer.split(";").collect();
                    let text = s.pop().unwrap_or(&"").trim();
                    let mut style = String::new();

                    for (i, mut x) in s.iter().enumerate() {
                        if i == 0 {
                            // color
                            if x == &"default" {
                                x = &"currentColor";
                            }

                            style.push_str(&format!("text-decoration-color: {x};"));
                        } else if i == 1 {
                            // style
                            if x == &"default" {
                                x = &"solid";
                            }

                            style.push_str(&format!("text-decoration-style: {x};"));
                        } else if i == 2 {
                            // line
                            if x == &"default" {
                                x = &"underline";
                            }

                            style.push_str(&format!("text-decoration-line: {x};"));
                        } else if i == 3 {
                            // thickness
                            if x == &"default" {
                                x = &"1px";
                            }

                            style.push_str(&format!("text-decoration-thickness: {x}px;"));
                        }
                    }

                    // defaults
                    if s.get(1).is_none() {
                        style.push_str(&format!("text-decoration-style: solid;"));
                    }

                    if s.get(2).is_none() {
                        style.push_str(&format!("text-decoration-line: underline;"));
                    }

                    if s.get(3).is_none() {
                        style.push_str(&format!("text-decoration-thickness: 1px;"));
                    }

                    // ...
                    output.push_str(&format!("<span style=\"{style}\">{text}</span>"));
                    buffer.clear();

                    open_1 = false;
                    is_open = false;
                    close_1 = false;
                    continue;
                }

                // open
                open_1 = true;

                // flush buffer
                output.push_str(&buffer);
                buffer.clear();
            }
            _ => buffer.push(char),
        }
    }
}

fn parse_comment_line(output: &mut String, _: &mut String, line: &str) {
    if line.contains("]:") && line.starts_with("[") {
        return;
    }

    if line == "[..]" {
        output.push_str("  ");
        return;
    }

    output.push_str(line);
}

fn parse_image_size_line(output: &mut String, buffer: &mut String, line: &str) {
    let mut image_possible = false;
    let mut in_image = false;
    let mut in_size = false;
    let mut in_size_rhs = false;

    let mut size_lhs = String::new();
    let mut size_rhs = String::new();

    if !line.contains("{") {
        output.push_str(line);
        return;
    }

    for char in line.chars() {
        if image_possible && char != '[' {
            image_possible = false;
            output.push('!');
        }

        match char {
            '[' => {
                if image_possible {
                    in_image = true;
                    image_possible = false;
                    continue;
                }

                if in_image {
                    buffer.push(char);
                } else {
                    output.push(char);
                }
            }
            '{' => {
                if in_image {
                    in_size = true;
                    continue;
                }

                if in_image {
                    buffer.push(char);
                } else {
                    output.push(char);
                }
            }
            ':' => {
                if in_size {
                    in_size_rhs = true;
                    continue;
                }

                if in_image {
                    buffer.push(char);
                } else {
                    output.push(char);
                }
            }
            '}' => {
                if in_size && in_size_rhs {
                    // end
                    output.push_str(&format!(
                        "<span style=\"width: {size_lhs}; height: {size_rhs}\" class=\"img_sizer\">![{buffer}</span>"
                    ));

                    size_lhs = String::new();
                    size_rhs = String::new();
                    in_image = false;
                    in_size = false;
                    in_size_rhs = false;
                    image_possible = false;

                    buffer.clear();
                    continue;
                }

                if in_image {
                    buffer.push(char);
                } else {
                    output.push(char);
                }
            }
            '!' => {
                // flush buffer
                output.push_str(&buffer);
                buffer.clear();

                // ...
                image_possible = true
            }
            _ => {
                if in_image {
                    if in_size {
                        if in_size_rhs {
                            size_rhs.push(char);
                        } else {
                            size_lhs.push(char);
                        }
                    } else {
                        buffer.push(char);
                    }
                } else {
                    output.push(char)
                }
            }
        }
    }
}

fn parse_image_line(output: &mut String, buffer: &mut String, line: &str) {
    let mut image_possible = false;
    let mut in_image = false;
    let mut in_alt = false;
    let mut in_src = false;
    let mut alt = String::new();

    for char in line.chars() {
        if image_possible && char != '[' {
            image_possible = false;
            output.push('!');
        }

        match char {
            '[' => {
                if image_possible {
                    in_image = true;
                    image_possible = false;
                    in_alt = true;
                    continue;
                }

                if in_image {
                    buffer.push(char);
                } else {
                    output.push(char);
                }
            }
            ']' => {
                if in_alt {
                    in_alt = false;
                    in_src = true;
                    continue;
                }

                output.push(char);
            }
            '(' => {
                if in_src {
                    continue;
                }

                if in_image {
                    buffer.push(char);
                } else {
                    output.push(char);
                }
            }
            ')' => {
                if in_image {
                    // end
                    output.push_str(&format!(
                        "<img loading=\"lazy\" alt=\"{alt}\" src=\"{buffer}\" />"
                    ));

                    alt = String::new();
                    in_alt = false;
                    in_src = false;
                    in_image = false;
                    image_possible = false;

                    buffer.clear();
                    continue;
                }

                output.push(char);
            }
            '!' => {
                // flush buffer
                output.push_str(&buffer);
                buffer.clear();

                // ...
                image_possible = true;
            }
            _ => {
                if in_image {
                    if in_alt {
                        alt.push(char)
                    } else {
                        buffer.push(char);
                    }
                } else {
                    output.push(char)
                }
            }
        }
    }
}

fn parse_link_line(output: &mut String, buffer: &mut String, line: &str) {
    let mut in_link = false;
    let mut in_text = false;
    let mut in_src = false;
    let mut text = String::new();

    for (i, char) in line.chars().enumerate() {
        match char {
            '[' => {
                // flush buffer
                output.push_str(&buffer);
                buffer.clear();

                // scan for closing, otherwise quit
                let haystack = &line[i..];

                if !haystack.contains("]") {
                    output.push('[');
                    continue;
                }

                // ...
                in_link = true;
                in_text = true;
            }
            ']' => {
                if in_text {
                    in_text = false;
                    in_src = true;
                    continue;
                }

                output.push(char);
            }
            '(' => {
                if in_src {
                    continue;
                }

                if in_link {
                    buffer.push(char);
                } else {
                    output.push(char);
                }
            }
            ')' => {
                if in_link {
                    // end
                    output.push_str(&format!(
                        "<a href=\"{buffer}\" rel=\"noopener noreferrer\">{text}</a>"
                    ));

                    text = String::new();
                    in_text = false;
                    in_src = false;
                    in_link = false;

                    buffer.clear();
                    continue;
                }

                output.push(char);
            }
            _ => {
                if in_link {
                    if in_text {
                        text.push(char)
                    } else {
                        buffer.push(char);
                    }
                } else {
                    output.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)
}

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

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

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

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

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