use rowan::NodeOrToken;
use crate::pipeline::Change;

pub fn apply_changes(content: &str, mut changes: Vec<Change>, debug: bool) -> String {
    let mut last_pos = 0;
    let mut ncontent = String::new();

    changes.sort_by_key(|change| change.node.text_range().start());

    for change in changes {
        use crate::queries::Operator::*;
        match change.kind {
            Remove => {
                let (before, after) = remove_node(&change.node);
                if last_pos > before { continue }
                ncontent += &content[last_pos..before];
                if debug {
                    println!("removing: {}", &content[before..after])
                }
                last_pos = after;
            }
            Keep => {
                let (before, after) = surrounding_noise(&change.node);
                let (before, after) = eat_whitespace(&before, &after);
                // let (before, after) = (change.node.text_range().start().into(), change.node.text_range().end().into());
                let (before, after) = (before.text_range().start().into(), after.text_range().end().into());
                if debug {
                    println!("keeping: {}", &content[before..after])
                };
                ncontent += &content[before..after];
                // last_pos = after;
            }
        }
    }

    ncontent += &content[last_pos..];

    ncontent
}



// TODO: does rnix really not have an alias for this?
type NixNodeOrToken = NodeOrToken<rowan::SyntaxNode<rnix::NixLanguage>, rowan::SyntaxToken<rnix::NixLanguage>>;

/// eat all tokens of the given kind (backwards or forwards)
fn eat_kind(node: &NixNodeOrToken, kind: rnix::SyntaxKind, backwards: bool) ->  NixNodeOrToken {
    let mut span = node.clone();

    loop {
        span = match if backwards { span.prev_sibling_or_token() } else { span.next_sibling_or_token() } {
            Some(NodeOrToken::Token(t))
                if t.kind() == kind
                => NodeOrToken::Token(t),
            _ => break
        };
    }
    span
}


/// eat whitespace outwards both ways
fn eat_whitespace(begin: &NixNodeOrToken, end: &NixNodeOrToken)
                  -> (NixNodeOrToken, NixNodeOrToken) {
    let begin = eat_kind(begin, rnix::SyntaxKind::TOKEN_WHITESPACE, true);
    let end = eat_kind(end, rnix::SyntaxKind::TOKEN_WHITESPACE, false);
    (begin, end)
}

/// for a node, get all the "syntactic noise" which surrounds it
/// (i.e. brackets, whitespace, etc.) which should be removed if
/// the node itself is removed, except the final bit of whitespace
/// potentially separating it from neighbouring nodes, which should
/// be handled separately to keep formatting nice
fn surrounding_noise(node: &rnix::SyntaxNode) -> (NixNodeOrToken, NixNodeOrToken) {

    fn eat_matching_parens(begin: &NixNodeOrToken, end: &NixNodeOrToken)
        -> Option<(NixNodeOrToken, NixNodeOrToken)> {
        match (begin.prev_sibling_or_token(), end.next_sibling_or_token()) {
            (Some(begin), Some(end))
                if begin.kind() == rnix::SyntaxKind::TOKEN_L_PAREN
                && end.kind() == rnix::SyntaxKind::TOKEN_R_PAREN
                => Some((begin, end)),
            _ => None
        }
    }

    let (mut begin, mut end): (NixNodeOrToken, NixNodeOrToken) =
        (NodeOrToken::Node(node.clone()), NodeOrToken::Node(node.clone()));

    loop {
        let (a, b) = eat_whitespace(&begin, &end);
        // println!("loop: {begin}, {end}");
        // println!("loop: {a}, {b}");
        // println!("{:?}", (begin.prev_sibling_or_token(), end.next_sibling_or_token()));
        if let Some(res) = eat_matching_parens(&a, &b) {
            // println!("ate parens!");
            (begin, end) = res;
        } else {
          break
        }
    }

    (begin, end)
}


fn remove_node(node: &rnix::SyntaxNode) -> (usize, usize) {
    let (before, after) = surrounding_noise(node);

    let (mut prev, /*mut*/ next) =
        eat_whitespace(&before, &after);

    // println!("{prev:?}, {next:?}");
    if let Some(t) = prev.as_token().map(|t| t.prev_token()).flatten() {
        if t.kind() == rnix::SyntaxKind::TOKEN_WHITESPACE {
            prev = NodeOrToken::Token(t);
        }
    };
    // if let Some(t) = next.as_token().map(|t| t.next_token()).flatten() {
    //     if t.kind() == rnix::SyntaxKind::TOKEN_WHITESPACE {
    //         next = NodeOrToken::Token(t);
    //     }
    // };
    // println!("{prev:?}, {next:?}");


    if prev.kind() == rnix::SyntaxKind::TOKEN_WHITESPACE
        && next.kind() == rnix::SyntaxKind::TOKEN_WHITESPACE {
            // println!("inside if!");
            if prev.to_string().lines().count() < next.to_string().lines().count() {
                let start: usize = (node.text_range().start() - prev.text_range().len()).into();
                let end: usize = node.text_range().end().into();
                (start + previous_indentation(&node).unwrap_or(0)
                 , end + next_indentation(&node).unwrap_or(0))
            } else {
                let start: usize = node.text_range().start().into();
                let end: usize = (node.text_range().end() + next.text_range().len()).into();
                (start, end)
                // (start - previous_indentation(&node).unwrap_or(0),
                //  end - next_indentation(&node).unwrap_or(0))
            }
        }
    else {
        (prev.text_range().start().into(), next.text_range().end().into())
    }
}

fn indentation_of_string(string: &str) -> Option<usize> {
    if string.contains("\n") {
        None
    } else {
        Some(string.lines().last().unwrap().len())
    }
}

fn previous_indentation(node: &rnix::SyntaxNode) -> Option<usize> {
    let whitespace_token = node.prev_sibling_or_token()?;

    if whitespace_token.kind() == rnix::SyntaxKind::TOKEN_WHITESPACE {
        indentation_of_string(&whitespace_token.to_string())
    } else {
        None
    }
}

fn next_indentation(node: &rnix::SyntaxNode) -> Option<usize> {
    let whitespace_token = node.next_sibling_or_token()?;

    if whitespace_token.kind() == rnix::SyntaxKind::TOKEN_WHITESPACE {
        indentation_of_string(&whitespace_token.to_string())
        // Some(whitespace_token.to_string().lines().last().unwrap().len())
    } else {
        None
    }
}