use unicode_script::{Script, UnicodeScript};

use crate::TextLineIndex;
use super::{Font, FontShapeGlyph, FontShapeLine, FontShapeSpan, FontShapeWord};
use super::fallback::{FontFallbackIter};

/// Fonts that match a pattern
pub struct FontMatches<'a> {
    pub locale: &'a str,
    pub fonts: Vec<Font<'a>>,
}

impl<'a> FontMatches<'a> {
    fn shape_fallback(
        &self,
        font: &'a Font<'a>,
        line: &str,
        start_word: usize,
        end_word: usize,
        span_rtl: bool,
    ) -> (Vec<FontShapeGlyph>, Vec<usize>) {
        let word = &line[start_word..end_word];

        let font_scale = font.rustybuzz.units_per_em() as f32;

        let mut buffer = rustybuzz::UnicodeBuffer::new();
        buffer.set_direction(if span_rtl {
            rustybuzz::Direction::RightToLeft
        } else {
            rustybuzz::Direction::LeftToRight
        });
        buffer.push_str(word);
        buffer.guess_segment_properties();

        let rtl = match buffer.direction() {
            rustybuzz::Direction::RightToLeft => true,
            //TODO: other directions?
            _ => false,
        };
        assert_eq!(rtl, span_rtl);

        let glyph_buffer = rustybuzz::shape(&font.rustybuzz, &[], buffer);
        let glyph_infos = glyph_buffer.glyph_infos();
        let glyph_positions = glyph_buffer.glyph_positions();

        let mut missing = Vec::new();
        let mut glyphs = Vec::with_capacity(glyph_infos.len());
        for (info, pos) in glyph_infos.iter().zip(glyph_positions.iter()) {
            let x_advance = pos.x_advance as f32 / font_scale;
            let y_advance = pos.y_advance as f32 / font_scale;
            let x_offset = pos.x_offset as f32 / font_scale;
            let y_offset = pos.y_offset as f32 / font_scale;

            //println!("  {:?} {:?}", info, pos);
            if info.glyph_id == 0 {
                missing.push(start_word + info.cluster as usize);
            }

            let inner = info.glyph_id as swash::GlyphId;
            glyphs.push(FontShapeGlyph {
                start: start_word + info.cluster as usize,
                end: end_word, // Set later
                x_advance,
                y_advance,
                x_offset,
                y_offset,
                font,
                inner,
            });
        }

        // Adjust end of glyphs
        if rtl {
            for i in 1..glyphs.len() {
                let next_start = glyphs[i - 1].start;
                let next_end = glyphs[i - 1].end;
                let prev = &mut glyphs[i];
                if prev.start == next_start {
                    prev.end = next_end;
                } else {
                    prev.end = next_start;
                }
            }
        } else {
            for i in (1..glyphs.len()).rev() {
                let next_start = glyphs[i].start;
                let next_end = glyphs[i].end;
                let prev = &mut glyphs[i - 1];
                if prev.start == next_start {
                    prev.end = next_end;
                } else {
                    prev.end = next_start;
                }
            }
        }

        (glyphs, missing)
    }

    fn shape_word(
        &self,
        line: &str,
        start_word: usize,
        end_word: usize,
        span_rtl: bool,
        blank: bool,
    ) -> FontShapeWord {
        //TODO: use smallvec?
        let mut scripts = Vec::new();
        for c in line[start_word..end_word].chars() {
            match c.script() {
                Script::Common |
                Script::Inherited |
                Script::Latin |
                Script::Unknown => (),
                script => if ! scripts.contains(&script) {
                    scripts.push(script);
                },
            }
        }

        log::trace!(
            "    Word {:?}{}: '{}'",
            scripts,
            if blank { " BLANK" } else { "" },
            &line[start_word..end_word],
        );

        //TODO: configure default family
        let mut font_iter = FontFallbackIter::new(
            &self.fonts,
            &["Fira Sans", "Fira Mono"],
            scripts,
            &self.locale
        );

        let (mut glyphs, mut missing) = self.shape_fallback(
            font_iter.next().unwrap(),
            line,
            start_word,
            end_word,
            span_rtl
        );

        //TODO: improve performance!
        while !missing.is_empty() {
            let font = match font_iter.next() {
                Some(some) => some,
                None => break,
            };

            log::trace!("Evaluating fallback with font '{}'", font.info.family);
            let (mut fb_glyphs, fb_missing) = self.shape_fallback(
                font,
                line,
                start_word,
                end_word,
                span_rtl
            );

            // Insert all matching glyphs
            let mut fb_i = 0;
            while fb_i < fb_glyphs.len() {
                let start = fb_glyphs[fb_i].start;
                let end = fb_glyphs[fb_i].end;

                // Skip clusters that are not missing, or where the fallback font is missing
                if !missing.contains(&start) || fb_missing.contains(&start) {
                    fb_i += 1;
                    continue;
                }

                let mut missing_i = 0;
                while missing_i < missing.len() {
                    if missing[missing_i] >= start && missing[missing_i] < end {
                        // println!("No longer missing {}", missing[missing_i]);
                        missing.remove(missing_i);
                    } else {
                        missing_i += 1;
                    }
                }

                // Find prior glyphs
                let mut i = 0;
                while i < glyphs.len() {
                    if glyphs[i].start >= start && glyphs[i].end <= end {
                        break;
                    } else {
                        i += 1;
                    }
                }

                // Remove prior glyphs
                while i < glyphs.len() {
                    if glyphs[i].start >= start && glyphs[i].end <= end {
                        let _glyph = glyphs.remove(i);
                        // log::trace!("Removed {},{} from {}", _glyph.start, _glyph.end, i);
                    } else {
                        break;
                    }
                }

                while fb_i < fb_glyphs.len() {
                    if fb_glyphs[fb_i].start >= start && fb_glyphs[fb_i].end <= end {
                        let fb_glyph = fb_glyphs.remove(fb_i);
                        // log::trace!("Insert {},{} from font {} at {}", fb_glyph.start, fb_glyph.end, font_i, i);
                        glyphs.insert(i, fb_glyph);
                        i += 1;
                    } else {
                        break;
                    }
                }
            }
        }

        // Debug missing font fallbacks
        font_iter.check_missing(&line[start_word..end_word]);

        /*
        for glyph in glyphs.iter() {
            log::trace!("'{}': {}, {}, {}, {}", &line[glyph.start..glyph.end], glyph.x_advance, glyph.y_advance, glyph.x_offset, glyph.y_offset);
        }
        */

        FontShapeWord { blank, glyphs }
    }

    fn shape_span(
        &self,
        line: &str,
        start_span: usize,
        end_span: usize,
        line_rtl: bool,
        span_rtl: bool,
    ) -> FontShapeSpan {
        let span = &line[start_span..end_span];

        log::trace!(
            "  Span {}: '{}'",
            if span_rtl { "RTL" } else { "LTR" },
            span
        );

        let mut words = Vec::new();

        let mut start_word = 0;
        for (end_lb, _) in unicode_linebreak::linebreaks(span) {
            let mut start_lb = end_lb;
            for (i, c) in span[start_word..end_lb].char_indices() {
                if start_word + i == end_lb {
                    break;
                } else if c.is_whitespace() {
                    start_lb = start_word + i;
                }
            }
            if start_word < start_lb {
                words.push(self.shape_word(
                    line,
                    start_span + start_word,
                    start_span + start_lb,
                    span_rtl,
                    false,
                ));
            }
            if start_lb < end_lb {
                words.push(self.shape_word(
                    line,
                    start_span + start_lb,
                    start_span + end_lb,
                    span_rtl,
                    true,
                ));
            }
            start_word = end_lb;
        }

        // Reverse glyphs in RTL lines
        if line_rtl {
            for word in words.iter_mut() {
                word.glyphs.reverse();
            }
        }

        // Reverse words in spans that do not match line direction
        if line_rtl != span_rtl {
            words.reverse();
        }

        FontShapeSpan {
            rtl: span_rtl,
            words,
        }
    }

    pub fn shape_line(&self, line_i: TextLineIndex, line: &str) -> FontShapeLine {
        let mut spans = Vec::new();

        let bidi = unicode_bidi::BidiInfo::new(line, None);
        let rtl = if bidi.paragraphs.is_empty() {
            false
        } else {
            assert_eq!(bidi.paragraphs.len(), 1);
            let para_info = &bidi.paragraphs[0];
            let line_rtl = para_info.level.is_rtl();

            log::trace!("Line {}: '{}'", if line_rtl { "RTL" } else { "LTR" }, line);

            let paragraph = unicode_bidi::Paragraph::new(&bidi, &para_info);

            let mut start = 0;
            let mut span_rtl = line_rtl;
            for i in paragraph.para.range.clone() {
                let next_rtl = paragraph.info.levels[i].is_rtl();
                if span_rtl != next_rtl {
                    spans.push(self.shape_span(line, start, i, line_rtl, span_rtl));
                    span_rtl = next_rtl;
                    start = i;
                }
            }
            spans.push(self.shape_span(line, start, line.len(), line_rtl, span_rtl));

            line_rtl
        };

        FontShapeLine { line_i, rtl, spans }
    }
}