//! Keyboard dispatch and normal-mode commands.
use crate::motion::{self, Find};
use crate::parse::{self, MAX_COUNT, Parsed};
use crate::{Doc, Error, ExCommand, Key, KeyCode, Mode, Outcome, Result, Vim};

impl Vim {
    pub(crate) fn handle_key(&mut self, key: Key, doc: &mut Doc, out: &mut Outcome) -> Result<bool> {
        if self.invalid_count {
            if !matches!(key.code, KeyCode::Char(ch) if ch.is_ascii_digit()) {
                self.invalid_count = false;
            }
            return Ok(true);
        }
        if self.mode == Mode::CommandLine {
            return self.command_key(key, doc, out);
        }
        if matches!(self.mode, Mode::Insert | Mode::Replace) {
            return self.insert_key(key, doc);
        }
        if key.code == KeyCode::Esc || key.ctrl && matches!(key.code, KeyCode::Char('[' | 'c')) {
            self.pending.clear();
            self.mode = Mode::Normal;
            doc.anchor = None;
            doc.normal_cursor();
            return Ok(true);
        }
        let Some(token) = key_token(key) else {
            return Ok(false);
        };
        let visual = matches!(self.mode, Mode::Visual | Mode::VisualLine);
        if self.pending.is_empty() && [":", "/", "?"].contains(&token.as_str()) {
            self.prompt = token.chars().next().unwrap_or(':');
            self.mode = Mode::CommandLine;
            self.command_line.clear();
            return Ok(true);
        }
        self.pending.push_str(&token);
        let Some(parsed) = parse::parse(&self.pending, visual)? else {
            return Ok(true);
        };
        self.pending.clear();
        self.execute(&parsed, doc, out)
    }

    fn execute(&mut self, parsed: &Parsed, doc: &mut Doc, out: &mut Outcome) -> Result<bool> {
        if let Some(operator) = parsed.operator {
            return self.apply_operator(operator, parsed, doc, out).map(|()| true);
        }
        let command = parsed.command.as_str();
        if matches!(self.mode, Mode::Visual | Mode::VisualLine) && ["~", "u", "U"].contains(&command) {
            let operator = match command {
                "u" => parse::Operator::Lower,
                "U" => parse::Operator::Upper,
                _ => parse::Operator::Toggle,
            };
            return self
                .apply_operator(
                    operator,
                    &Parsed {
                        count: parsed.count,
                        explicit: parsed.explicit,
                        register: parsed.register,
                        operator: Some(operator),
                        command: "selection".into(),
                    },
                    doc,
                    out,
                )
                .map(|()| true);
        }
        let count = parsed.count;
        match command {
            "i" => self.enter_insert(Mode::Insert, count),
            "a" => {
                doc.cursor = doc.next(doc.cursor);
                self.enter_insert(Mode::Insert, count);
            }
            "I" => {
                doc.cursor = first_nonblank(doc, doc.cursor);
                self.enter_insert(Mode::Insert, count);
            }
            "A" => {
                doc.cursor = doc.line_end(doc.cursor);
                self.enter_insert(Mode::Insert, count);
            }
            "R" => self.enter_insert(Mode::Replace, count),
            "o" | "O" => self.open_line(doc, command == "o", count)?,
            "v" | "V" => {
                let target = if command == "v" { Mode::Visual } else { Mode::VisualLine };
                if self.mode == target {
                    self.mode = Mode::Normal;
                    doc.anchor = None;
                } else {
                    if doc.anchor.is_none() {
                        doc.anchor = Some(doc.cursor);
                    }
                    self.mode = target;
                }
            }
            "x" | "X" | "s" | "S" | "C" | "D" | "Y" => self.single_operator(parsed, doc, out)?,
            "p" | "P" => self.paste(doc, parsed, command == "p")?,
            "J" => Self::join(doc, count)?,
            "~" => Self::toggle(doc, count)?,
            "u" | "<C-r>" => {
                self.repeat.history_action = true;
                for _ in 0..count {
                    let changed = if command == "u" { self.history.undo(doc) } else { self.history.redo(doc) };
                    if !changed {
                        break;
                    }
                }
                doc.anchor = None;
                doc.normal_cursor();
            }
            "." => self.dot(doc, out, count)?,
            "n" | "N" => self.search_next(doc, command == "N", count)?,
            "*" => {
                self.search.word(doc)?;
                self.search_next(doc, false, count)?;
            }
            "gx" | "gf" => {
                if has_link(doc, command == "gf") {
                    out.ex = Some(if command == "gf" { ExCommand::OpenWikilink } else { ExCommand::FollowLink });
                } else {
                    return Err(Error::Invalid("no link under cursor".into()));
                }
            }
            "za" => out.ex = Some(ExCommand::Fold),
            "gt" => out.ex = Some(ExCommand::NextBuffer),
            "gT" => out.ex = Some(ExCommand::PrevBuffer),
            _ => return self.other_command(parsed, doc),
        }
        Ok(true)
    }

    fn other_command(&mut self, parsed: &Parsed, doc: &mut Doc) -> Result<bool> {
        let mut chars = parsed.command.chars();
        let first = chars.next();
        let second = chars.next();
        if first == Some('m') && second.is_some_and(|mark| mark.is_ascii_lowercase()) && chars.next().is_none() {
            if let Some(mark) = second {
                self.marks.insert(mark, doc.cursor);
            }
            return Ok(true);
        }
        if matches!(first, Some('\'' | '`')) && chars.next().is_none() {
            let mark = second.ok_or_else(|| Error::Invalid("missing mark".into()))?;
            let position = *self.marks.get(&mark).ok_or_else(|| Error::Invalid("mark not set".into()))?;
            if !doc.text.is_char_boundary(position) {
                return Err(Error::Invalid("mark outside document".into()));
            }
            doc.cursor = if first == Some('\'') { first_nonblank(doc, position) } else { position };
            return Ok(true);
        }
        if first == Some('r') && chars.next().is_none() {
            return Self::replace_character(doc, second, parsed.count).map(|()| true);
        }
        if matches!(self.mode, Mode::Visual | Mode::VisualLine) && matches!(first, Some('i' | 'a')) && chars.next().is_none() {
            let range = second
                .and_then(|kind| crate::textobject::range(doc, kind, first == Some('a'), parsed.count))
                .ok_or_else(|| Error::Invalid("text object not found".into()))?;
            doc.anchor = Some(range.start);
            doc.cursor = doc.prev(range.end);
            return Ok(true);
        }
        let Some(target) = motion::resolve(doc, &parsed.command, parsed.count, parsed.explicit, self.viewport, self.last_find) else {
            return Ok(false);
        };
        self.remember_find(&parsed.command);
        doc.cursor = target.target;
        doc.normal_cursor();
        Ok(true)
    }

    pub(crate) fn remember_find(&mut self, command: &str) {
        let mut chars = command.chars();
        if let (Some(kind @ ('f' | 'F' | 't' | 'T')), Some(needle)) = (chars.next(), chars.next()) {
            self.last_find = Some(Find { needle, forward: kind.is_lowercase(), till: matches!(kind, 't' | 'T') });
        }
    }

    pub(crate) fn search_next(&self, doc: &mut Doc, reverse: bool, count: usize) -> Result<()> {
        doc.cursor = self.search.find(doc, reverse, count).ok_or_else(|| Error::Invalid("pattern not found".into()))?;
        Ok(())
    }

    fn dot(&mut self, doc: &mut Doc, out: &mut Outcome, count: usize) -> Result<()> {
        if self.repeat.replaying {
            return Err(Error::Invalid("recursive repeat".into()));
        }
        self.repeat.dot_action = true;
        let keys = self.repeat.last.clone();
        if keys.len().checked_mul(count).is_none_or(|size| size > MAX_COUNT) {
            return Err(Error::Limit("repeat execution"));
        }
        self.repeat.replaying = true;
        for _ in 0..count {
            for key in &keys {
                let effect = self.handle(*key, doc);
                if effect.message.is_some() {
                    self.repeat.replaying = false;
                    return Err(Error::Invalid(effect.message.unwrap_or_default()));
                }
                if effect.clipboard_set.is_some() {
                    out.clipboard_set = effect.clipboard_set;
                }
            }
        }
        self.repeat.replaying = false;
        Ok(())
    }
}

pub(crate) fn first_nonblank(doc: &Doc, pos: usize) -> usize {
    let start = doc.line_start(pos);
    doc.slice(start, doc.line_end(start))
        .and_then(|line| line.char_indices().find(|(_, ch)| !ch.is_whitespace()))
        .map_or(start, |(offset, _)| start.saturating_add(offset))
}

fn key_token(key: Key) -> Option<String> {
    if key.alt {
        return None;
    }
    if key.ctrl {
        return match key.code {
            KeyCode::Char(ch @ ('r' | 'd' | 'u')) => Some(format!("<C-{ch}>")),
            _ => None,
        };
    }
    Some(match key.code {
        KeyCode::Char(ch) => ch.to_string(),
        KeyCode::Left | KeyCode::Backspace => "h".into(),
        KeyCode::Right => "l".into(),
        KeyCode::Up => "k".into(),
        KeyCode::Down | KeyCode::Enter => "j".into(),
        KeyCode::Home => "0".into(),
        KeyCode::End => "$".into(),
        KeyCode::PageUp => "<C-u>".into(),
        KeyCode::PageDown => "<C-d>".into(),
        KeyCode::Tab | KeyCode::F(_) | KeyCode::Esc => return None,
    })
}

fn has_link(doc: &Doc, wiki_only: bool) -> bool {
    let start = doc.line_start(doc.cursor);
    let end = doc.line_end(doc.cursor);
    let Some(line) = doc.slice(start, end) else {
        return false;
    };
    let cursor = doc.cursor.saturating_sub(start);
    for (offset, _) in line.match_indices("[[") {
        if let Some(close) = line.get(offset.saturating_add(2)..).and_then(|tail| tail.find("]]")) {
            let finish = offset.saturating_add(2).saturating_add(close).saturating_add(2);
            if cursor >= offset && cursor < finish {
                return true;
            }
        }
    }
    if wiki_only {
        return false;
    }
    for (offset, _) in line.match_indices('[') {
        if let Some(tail) = line.get(offset..)
            && let Some(separator) = tail.find("](")
            && let Some(close) = tail.get(separator.saturating_add(2)..).and_then(|part| part.find(')'))
        {
            let finish = offset.saturating_add(separator).saturating_add(2).saturating_add(close).saturating_add(1);
            if cursor >= offset && cursor < finish {
                return true;
            }
        }
    }
    false
}

#[cfg(test)]
mod tests {
    use super::*;
    #[test]
    fn host_modifiers_are_not_inserted_into_pending_commands() {
        let mut vim = Vim::new();
        let mut doc = Doc::new("text".into()).unwrap();
        let effect = vim.handle(Key { alt: true, ..Key::char('x') }, &mut doc);
        assert!(!effect.consumed);
        assert_eq!(vim.pending(), "");
    }
    #[test]
    fn markdown_effects_require_a_link_at_cursor() {
        let mut doc = Doc::new("[label](note) outside".into()).unwrap();
        assert!(has_link(&doc, false));
        assert!(!has_link(&doc, true));
        doc.cursor = doc.text.find("outside").unwrap();
        assert!(!has_link(&doc, false));
    }
}