//! Text objects: the word, the quoted text or the bracketed text the cursor
//! is in, for `diw`, `ca"` or `yi(`.

use std::ops::Range;

use super::motion::{Class, class_at, line_end, line_start, next, previous};
use crate::input::command::TextObject;

/// What a text object covers at `at` (with its edges when `around`), or
/// `None` when the cursor isn't in one.
pub fn range(text: &str, at: usize, object: TextObject, around: bool) -> Option<Range<usize>> {
    match object {
        TextObject::Word => word(text, at, around),
        TextObject::Quotes => quotes(text, at, around),
        TextObject::Parens => parens(text, at, around),
    }
}

/// `iw`: the word (or the run of spaces) the cursor is on. `aw`: the word
/// and the spaces after it, or else the ones before it.
fn word(text: &str, at: usize, around: bool) -> Option<Range<usize>> {
    let (start, end) = (line_start(text, at), line_end(text, at));
    let class = class_at(text, at).filter(|_| at < end)?;
    let run = |from: usize, class: Class| {
        let mut to = from;
        while to < end && class_at(text, to) == Some(class) {
            to = next(text, to);
        }
        to
    };
    let mut first = at;
    while first > start && class_at(text, previous(text, first)) == Some(class) {
        first = previous(text, first);
    }
    let last = run(at, class);
    if !around {
        return Some(first..last);
    }
    if class == Class::Blank {
        // On spaces, `aw` takes them and the word after.
        return Some(first..class_at(text, last).map_or(last, |after| run(last, after)));
    }
    let spaces_after = run(last, Class::Blank);
    if spaces_after > last {
        return Some(first..spaces_after);
    }
    let mut spaces_before = first;
    while spaces_before > start && class_at(text, previous(text, spaces_before)) == Some(Class::Blank) {
        spaces_before = previous(text, spaces_before);
    }
    Some(spaces_before..last)
}

/// `i"`: the text between the quotes the cursor is in or on, on its line;
/// the first quoted text after the cursor when it's in none. `a"`: the
/// quotes too, and the spaces after them (or else before), as in vim.
fn quotes(text: &str, at: usize, around: bool) -> Option<Range<usize>> {
    let (start, end) = (line_start(text, at), line_end(text, at));
    let quotes: Vec<usize> = text[start..end].match_indices('"').map(|(found, _)| start + found).collect();
    let (open, close) = match quotes.iter().position(|&quote| quote == at) {
        Some(index) if index % 2 == 0 => (index, index + 1),
        Some(index) => (index - 1, index),
        None => {
            let before = quotes.iter().filter(|&&quote| quote < at).count();
            if before % 2 == 1 { (before - 1, before) } else { (before, before + 1) }
        }
    };
    let (open, close) = (*quotes.get(open)?, *quotes.get(close)?);
    if !around {
        return Some(open + 1..close);
    }
    // Quotes and spaces are one byte each.
    let after = close + 1 + text[close + 1..end].len() - text[close + 1..end].trim_start_matches(' ').len();
    let before = if after > close + 1 { open } else { start + text[start..open].trim_end_matches(' ').len() };
    Some(before..after)
}

/// `i(`: what's between the brackets around the cursor (they can be on
/// other lines). `a(`: the brackets too.
fn parens(text: &str, at: usize, around: bool) -> Option<Range<usize>> {
    let open = if text[at..].starts_with('(') {
        at
    } else {
        let mut depth = 0;
        let mut found = None;
        for (index, c) in text[..at].char_indices().rev() {
            match c {
                ')' => depth += 1,
                '(' if depth == 0 => {
                    found = Some(index);
                    break;
                }
                '(' => depth -= 1,
                _ => {}
            }
        }
        found?
    };
    let mut depth = 0;
    let mut close = None;
    for (index, c) in text[open + 1..].char_indices() {
        match c {
            '(' => depth += 1,
            ')' if depth == 0 => {
                close = Some(open + 1 + index);
                break;
            }
            ')' => depth -= 1,
            _ => {}
        }
    }
    let close = close?;
    Some(if around { open..close + 1 } else { open + 1..close })
}

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

    /// The text an object covers, the cursor at '|' in `marked`.
    fn covered(marked: &str, object: TextObject, around: bool) -> Option<String> {
        let at = marked.find('|').unwrap();
        let text = marked.replacen('|', "", 1);
        range(&text, at, object, around).map(|range| text[range].to_string())
    }

    #[test]
    fn words() {
        assert_eq!(covered("raised b|eds here", TextObject::Word, false).unwrap(), "beds");
        assert_eq!(covered("raised b|eds here", TextObject::Word, true).unwrap(), "beds ");
        assert_eq!(covered("raised b|eds", TextObject::Word, true).unwrap(), " beds", "no space after");
        assert_eq!(covered("raised |  beds", TextObject::Word, true).unwrap(), "   beds", "on spaces");
        assert_eq!(covered("|", TextObject::Word, false), None, "nothing on an empty line");
    }

    #[test]
    fn quotes_and_brackets() {
        let quoted = "say \"hi there\" now";
        assert_eq!(covered("say \"hi th|ere\" now", TextObject::Quotes, false).unwrap(), "hi there");
        assert_eq!(covered("say \"hi th|ere\" now", TextObject::Quotes, true).unwrap(), "\"hi there\" ");
        assert_eq!(
            covered("s|ay \"hi there\" now", TextObject::Quotes, false).unwrap(),
            "hi there",
            "the next pair"
        );
        assert_eq!(covered(&format!("{quoted}|"), TextObject::Quotes, false), None);
        assert_eq!(covered("f(a, (b|), c)", TextObject::Parens, false).unwrap(), "b");
        assert_eq!(covered("f(a, (b), |c)", TextObject::Parens, true).unwrap(), "(a, (b), c)");
        assert_eq!(covered("f(a,\n|b)", TextObject::Parens, false).unwrap(), "a,\nb", "across lines");
        assert_eq!(covered("no |brackets", TextObject::Parens, false), None);
    }
}