use regex::Regex;

/// Convert the Xpath selectors to CSS selector
///
/// ## Things it supports
/// Any tag (including *), contains(), text(), indexed, any attribute (@id, @class, @anything).
///
/// ## Things it does not support
/// Move up to a parent tag (//a/../p) and maybe something else I'm not aware of...
///
/// ## Examples
///
/// Basic usage:
/// ```
/// let result = cssifier::cssifier("//a/p");
/// assert_eq!(result, Some("a p".to_string()));
///
/// let result = cssifier::cssifier("//a/p[@id='hello']");
/// assert_eq!(result, Some("a p#hello".to_string()));
///
/// let result = cssifier::cssifier("//a/p[contains(text(), 'hello')]");
/// assert_eq!(result, Some("a p:contains(hello)".to_string()));
///
/// let result = cssifier::cssifier("*random selector//*"); // Invalid selectors throw a empty string (WIP)
/// assert_eq!(result, Some("".to_string()));
/// ```
pub fn cssifier<S: AsRef<str>>(xpath: S) -> Option<String> {
    // Trait to &str
    let xpath = xpath.as_ref();

    // Ultra magic regex to parse XPath selectors
    let reg = Regex::new(r#"(?P<node>(^id\(["']?(?P<idvalue>\s*[\w/:][-/\w\s,:;.]*)["']?\)|(?P<nav>//?)(?P<tag>([a-zA-Z][a-zA-Z0-9]{0,10}|\*))(\[((?P<matched>(?P<mattr>@?[.a-zA-Z_:][-\w:.]*(\(\))?)=["'](?P<mvalue>\s*[\w/:][-/\w\s,:;.]*))["']|(?P<contained>contains\((?P<cattr>@?[.a-zA-Z_:][-\w:.]*(\(\))?),\s*["'](?P<cvalue>\s*[\w/:][-/\w\s,:;.]*)["']\)))\])?(\[(?P<nth>\d)\])?))"#).unwrap();
    let mut css = String::new();
    let mut position = 0;

    while position < xpath.len() {
        let node = reg.captures(&xpath[position..])?;
        let find = reg.find(&xpath[position..])?;

        // See the nav identifier
        let nav = match position {
            0 => "",
            _ => {
                if node.name("nav")?.as_str() != "//" {
                    " "
                } else {
                    " > "
                }
            }
        };

        // See the tag name
        let tag = if node.name("tag")?.as_str() == "*" {
            ""
        } else {
            match node.name("tag") {
                Some(tag) => tag.as_str(),
                _ => "",
            }
        };

        // See the idenfitier attribute of the tag
        let attr = if node.name("idvalue").is_some() {
            format!("#{}", node.name("idvalue")?.as_str().replace(" ", "#"))
        } else if node.name("matched").is_some() {
            let mattr = node.name("mattr")?.as_str();
            let mvalue = node.name("mvalue")?.as_str();

            if mattr == "@id" {
                format!("#{}", mvalue.replace(" ", "#"))
            } else if mattr == "@class" {
                format!(".{}", mvalue.replace(" ", "."))
            } else if mattr == "text()" || mattr == "." {
                format!(":contains(^{}$)", mvalue)
            } else if !mattr.is_empty() {
                let new_mvalue = if mvalue.contains(' ') {
                    format!("\"{}\"", mvalue)
                } else {
                    mvalue.to_string()
                };
                format!("[{}={}]", mattr.replace("@", ""), new_mvalue)
            } else {
                String::from("")
            }
        } else if node.name("contained").is_some() {
            let cattr = node.name("cattr")?.as_str();
            let cvalue = node.name("cvalue")?.as_str();

            if cattr.starts_with('@') {
                format!("[{}*={}]", cattr.replace("@", ""), cvalue)
            } else if cattr == "text()" {
                format!(":contains({})", cvalue)
            } else {
                String::from("")
            }
        } else {
            String::from("")
        };

        // See the child type
        let nth = if node.name("nth").is_some() {
            format!(":nth-of-type({})", node.name("nth")?.as_str())
        } else {
            String::from("")
        };

        // Paste all the magic :sparkles:
        css = format!("{}{}{}{}{}", css, nav, tag, attr, nth);
        position += find.end();
    }

    Some(css)
}

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

    #[test]
    fn it_works() {
        assert_eq!(cssifier("//a/b").unwrap(), "a b");
        assert_eq!(cssifier("//a/b[@id='hello']").unwrap(), "a b#hello");
        assert_eq!(
            cssifier("//a/b[contains(text(), 'hello')]").unwrap(),
            "a b:contains(hello)"
        );
        assert_eq!(cssifier("*random shit//*").unwrap(), "");
    }
}