// Copyright (c) 2022 Marceline Cramer
// SPDX-License-Identifier: Apache-2.0

use std::collections::HashMap;

use canary_script::api::{DrawContext, Font, TextLayout};
use canary_script::{Color, Vec2};

#[derive(Default)]
pub struct TextCache {
    layouts: Vec<OwnedText>,
    fonts: Vec<HashMap<String, usize>>,
}

impl TextCache {
    pub fn insert(&mut self, font: Font, text: &str) -> (usize, f32) {
        let font_idx = font.get_id() as usize;
        if let Some(font_cache) = self.fonts.get(font_idx) {
            if let Some(layout_idx) = font_cache.get(text) {
                return (*layout_idx, self.get(*layout_idx).width);
            }
        } else {
            let new_size = font_idx + 1;
            self.fonts.resize_with(new_size, Default::default);
        }

        let index = self.layouts.len();
        let layout = TextLayout::new(&font, text);
        let width = layout.get_bounds().width().max(0.0);

        self.layouts.push(OwnedText {
            font,
            layout,
            width,
        });

        self.fonts[font_idx].insert(text.to_string(), index);

        (index, width)
    }

    pub fn get(&self, index: usize) -> Text<'_> {
        self.layouts[index].borrow()
    }
}

/// Processed text that can be laid out.
pub struct Content {
    pub words: Vec<Word>,
}

impl Content {
    pub fn from_plain(cache: &mut TextCache, font: Font, text: &str) -> Self {
        use textwrap::word_splitters::{split_words, WordSplitter};
        use textwrap::WordSeparator;

        let separator = WordSeparator::new();
        let words = separator.find_words(text);

        // TODO: crate feature to enable hyphenation support?
        let splitter = WordSplitter::NoHyphenation;
        let split_words = split_words(words, &splitter);

        let mut words = Vec::new();
        for split_word in split_words {
            let (word, word_width) = cache.insert(font, split_word.word);
            let (whitespace, whitespace_width) = cache.insert(font, "_");
            let (penalty, penalty_width) = cache.insert(font, split_word.penalty);

            words.push(Word {
                word,
                word_width,
                whitespace,
                whitespace_width,
                penalty,
                penalty_width,
            });
        }

        Self { words }
    }

    pub fn layout(&self, cache: &TextCache, width: f32) -> Layout {
        use textwrap::wrap_algorithms::wrap_optimal_fit;
        let fragments = self.words.as_slice();
        let line_widths = &[width as f64];
        let penalties = Default::default();

        // Should never fail with reasonable input. Check [wrap_optimal_fit] docs for more info.
        let wrapped_lines = wrap_optimal_fit(fragments, line_widths, &penalties).unwrap();

        let mut lines = Vec::new();
        for line in wrapped_lines {
            lines.push(Line::from_word_line(cache, line));
        }

        Layout { lines }
    }
}

/// An atomic fragment of processed text that is ready to be laid out.
///
/// May or may not correspond to a single English "word".
///
/// Please see [textwrap::core::Word] and [textwrap::core::Fragment] for more information.
#[derive(Debug)]
pub struct Word {
    pub word: usize,
    pub word_width: f32,
    pub whitespace: usize,
    pub whitespace_width: f32,
    pub penalty: usize,
    pub penalty_width: f32,
}

impl textwrap::core::Fragment for Word {
    fn width(&self) -> f64 {
        self.word_width as f64
    }

    fn whitespace_width(&self) -> f64 {
        self.whitespace_width as f64
    }

    fn penalty_width(&self) -> f64 {
        self.penalty_width as f64
    }
}

#[derive(Debug)]
pub struct OwnedText {
    pub font: Font,
    pub layout: TextLayout,
    pub width: f32,
}

impl OwnedText {
    pub fn borrow(&self) -> Text<'_> {
        Text {
            font: self.font,
            layout: &self.layout,
            width: self.width,
        }
    }
}

/// A single piece of renderable text.
#[derive(Debug)]
pub struct Text<'a> {
    /// The font that this fragment has been laid out with.
    pub font: Font,

    /// The draw-ready [TextLayout] of this fragment.
    pub layout: &'a TextLayout,

    /// The width of this text.
    pub width: f32,
}

/// A finished, wrapped text layout.
pub struct Layout {
    pub lines: Vec<Line>,
}

impl Layout {
    pub fn draw(
        &self,
        cache: &TextCache,
        ctx: &DrawContext,
        scale: f32,
        line_height: f32,
        color: Color,
    ) {
        let mut cursor = Vec2::ZERO;
        for line in self.lines.iter() {
            let ctx = ctx.with_offset(cursor);
            line.draw(cache, &ctx, scale, color);
            cursor.y += line_height;
        }
    }
}

/// A finished line of a layout.
pub struct Line {
    pub fragments: Vec<Fragment>,
}

impl Line {
    pub fn from_word_line(cache: &TextCache, words: &[Word]) -> Self {
        let last_idx = words.len() - 1;
        let mut fragments = Vec::new();

        let mut add_word = |index: usize, hidden: bool| {
            let text = cache.get(index);

            fragments.push(Fragment {
                font: text.font,
                text: index,
                offset: Vec2::ZERO,
                advance: text.width,
                hidden,
            });
        };

        for (idx, word) in words.iter().enumerate() {
            add_word(word.word, false);

            if idx == last_idx {
                add_word(word.penalty, false);
            } else {
                add_word(word.whitespace, true);
            }
        }

        Self { fragments }
    }

    pub fn draw(&self, cache: &TextCache, ctx: &DrawContext, scale: f32, color: Color) {
        let mut cursor = Vec2::ZERO;
        for fragment in self.fragments.iter() {
            if !fragment.hidden {
                let text = cache.get(fragment.text);
                let offset = cursor + fragment.offset;
                ctx.draw_text_layout(text.layout, offset, scale, color);
            }

            cursor.x += fragment.advance * scale;
        }
    }
}

/// A finished fragment in a layout.
pub struct Fragment {
    /// The font of this fragment.
    pub font: Font,

    /// The index into the [TextCache] of the content of this fragment.
    pub text: usize,

    /// The offset for drawing the text layout.
    pub offset: Vec2,

    /// The horizontal advance to draw the next fragment.
    pub advance: f32,

    /// Whether this fragment should be skipped while drawing.
    pub hidden: bool,
}