//! Configurable checkbox progress palette (vimwiki's `g:vimwiki_listsyms`).
//!
//! A palette is a progression of glyphs from "empty" (index 0) to "done"
//! (the last index). The default `" .oOX"` is the stock vimwiki palette.
//! A separate `rejected` glyph (`-`) is fixed by convention.
//!
//! The palette maps glyphs to a normalised five-bucket [`CheckboxState`] for
//! the AST (so the HTML renderer keeps its fixed `done0..done4` classes) while
//! still letting the LSP cycle/toggle commands operate on the real glyphs.

use crate::ast::CheckboxState;

const REJECTED: char = '-';

/// An ordered checkbox progress palette. Always holds at least two glyphs.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct ListSyms {
    progression: Vec<char>,
}

impl Default for ListSyms {
    fn default() -> Self {
        Self {
            progression: " .oOX".chars().collect(),
        }
    }
}

impl ListSyms {
    /// Build a palette from a glyph string. Falls back to the default when
    /// fewer than two glyphs are supplied (a one-symbol palette can't express
    /// both "empty" and "done").
    pub fn new(s: &str) -> Self {
        let progression: Vec<char> = s.chars().collect();
        if progression.len() < 2 {
            Self::default()
        } else {
            Self { progression }
        }
    }

    pub fn len(&self) -> usize {
        self.progression.len()
    }

    pub fn is_empty(&self) -> bool {
        self.progression.is_empty()
    }

    pub fn empty_glyph(&self) -> char {
        self.progression[0]
    }

    pub fn done_glyph(&self) -> char {
        *self.progression.last().unwrap()
    }

    pub fn rejected_glyph(&self) -> char {
        REJECTED
    }

    pub fn glyph_at(&self, index: usize) -> char {
        self.progression[index.min(self.progression.len() - 1)]
    }

    pub fn index_of(&self, c: char) -> Option<usize> {
        self.progression.iter().position(|&g| g == c)
    }

    /// Progress rate (0..=100) for a glyph index.
    pub fn rate(&self, index: usize) -> i32 {
        let last = (self.progression.len() - 1) as i32;
        (index as i32) * 100 / last
    }

    /// Normalised five-bucket [`CheckboxState`] for a glyph, or `None` when the
    /// glyph is not part of this palette (and is not the rejected marker).
    pub fn state_of(&self, c: char) -> Option<CheckboxState> {
        if c == REJECTED {
            return Some(CheckboxState::Rejected);
        }
        let index = self.index_of(c)?;
        let rate = self.rate(index);
        // Round the rate to the nearest 25% bucket.
        Some(match (rate + 12) / 25 {
            0 => CheckboxState::Empty,
            1 => CheckboxState::Quarter,
            2 => CheckboxState::Half,
            3 => CheckboxState::ThreeQuarters,
            _ => CheckboxState::Done,
        })
    }

    /// Snap a rate (`-1` = rejected, else 0..=100) to a glyph. Intermediate
    /// rates distribute over the `n - 2` non-terminal glyphs using vimwiki's
    /// `ceil` rule, matching the stock five-symbol behaviour.
    pub fn glyph_for_rate(&self, rate: i32) -> char {
        if rate < 0 {
            return REJECTED;
        }
        if rate <= 0 {
            return self.empty_glyph();
        }
        if rate >= 100 {
            return self.done_glyph();
        }
        let mids = (self.progression.len().saturating_sub(2)).max(1) as f64;
        let index = ((rate as f64) / 100.0 * mids).ceil() as usize;
        self.glyph_at(index)
    }
}

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

    #[test]
    fn default_palette_matches_stock_vimwiki() {
        let s = ListSyms::default();
        assert_eq!(s.len(), 5);
        assert_eq!(s.empty_glyph(), ' ');
        assert_eq!(s.done_glyph(), 'X');
        assert_eq!(s.rejected_glyph(), '-');
        assert_eq!(s.rate(0), 0);
        assert_eq!(s.rate(1), 25);
        assert_eq!(s.rate(2), 50);
        assert_eq!(s.rate(3), 75);
        assert_eq!(s.rate(4), 100);
    }

    #[test]
    fn default_state_of_round_trips_each_glyph() {
        let s = ListSyms::default();
        assert_eq!(s.state_of(' '), Some(CheckboxState::Empty));
        assert_eq!(s.state_of('.'), Some(CheckboxState::Quarter));
        assert_eq!(s.state_of('o'), Some(CheckboxState::Half));
        assert_eq!(s.state_of('O'), Some(CheckboxState::ThreeQuarters));
        assert_eq!(s.state_of('X'), Some(CheckboxState::Done));
        assert_eq!(s.state_of('-'), Some(CheckboxState::Rejected));
        assert_eq!(s.state_of('?'), None);
    }

    #[test]
    fn default_glyph_for_rate_matches_legacy_buckets() {
        let s = ListSyms::default();
        assert_eq!(s.glyph_for_rate(-1), '-');
        assert_eq!(s.glyph_for_rate(0), ' ');
        assert_eq!(s.glyph_for_rate(25), '.');
        assert_eq!(s.glyph_for_rate(50), 'o');
        assert_eq!(s.glyph_for_rate(75), 'O');
        assert_eq!(s.glyph_for_rate(100), 'X');
    }

    #[test]
    fn short_input_falls_back_to_default() {
        assert_eq!(ListSyms::new(""), ListSyms::default());
        assert_eq!(ListSyms::new("x"), ListSyms::default());
    }

    #[test]
    fn custom_palette_buckets_to_nearest_state() {
        // 3 glyphs → rates 0 / 50 / 100.
        let s = ListSyms::new(" x✓");
        assert_eq!(s.state_of(' '), Some(CheckboxState::Empty));
        assert_eq!(s.state_of('x'), Some(CheckboxState::Half));
        assert_eq!(s.state_of('✓'), Some(CheckboxState::Done));
        assert_eq!(s.glyph_for_rate(50), 'x');
        assert_eq!(s.glyph_for_rate(100), '✓');
    }
}