use crate::composite::{Composite, CompositeStyle};
use crate::compound::Compound;
use crate::line::*;
use crate::tbl::{TableRow};
use std::cmp;

/// count the number of '#' at start. Return 0 if they're
/// not followed by a ' ' or if they're too many
fn header_level(src: &str) -> usize {
    let src = src.as_bytes();
    let mut l: usize = src.len();
    if l > 2 {
        l = cmp::min(src.len() - 1, MAX_HEADER_DEPTH + 1);
        for i in 0..l {
            match src[i] {
                b'#' => {}
                b' ' => {
                    return i;
                }
                _ => {
                    return 0;
                }
            }
        }
    }
    0
}

#[test]
fn header_level_count() {
    assert_eq!(header_level(""), 0);
    assert_eq!(header_level("#"), 0);
    assert_eq!(header_level("# "), 0); // we don't allow empty headers
    assert_eq!(header_level("# A"), 1);
    assert_eq!(header_level(" "), 0);
    assert_eq!(header_level("test"), 0);
    assert_eq!(header_level("###b"), 0);
    assert_eq!(header_level("###"), 0);
    assert_eq!(header_level("### b"), 3);
    assert_eq!(header_level(" a b"), 0);
    assert_eq!(header_level("# titre"), 1);
    assert_eq!(header_level("#### *titre*"), 4);
    assert_eq!(header_level("######## a b"), 8);
    assert_eq!(header_level("######### a b"), 0); // too deep
}

/// The structure parsing a line or part of a line.
/// A LineParser initialized from a markdown string exposes 2 main methods:
/// * `line` parses a line which is supposed to be part of a markdown text. This
///       method shouln't really be used externally: a text can be parsed in a whole
///       using `Text::from`
/// * `inline` parses a snippet which isn't supposed to be part of a markdown text.
///       Some types of lines aren't produced this ways as they don't make sense out of
///       a text: ListItem, TableRow, Code.
///
/// Normally not used directly but though `line::from(str)`
pub struct LineParser<'s> {
    src: &'s str,
    idx: usize, // current index in string, in bytes
    bold: bool,
    italic: bool,
    code: bool,
}

impl<'s> LineParser<'s> {
    pub fn from(src: &'s str) -> LineParser<'_> {
        LineParser {
            src,
            idx: 0,
            bold: false,
            italic: false,
            code: false,
        }
    }
    fn close_compound(&mut self, end: usize, tag_length: usize, compounds: &mut Vec<Compound<'s>>) {
        if end > self.idx {
            compounds.push(Compound::new(
                &self.src,
                self.idx,
                end,
                self.bold,
                self.italic,
                self.code,
            ));
        }
        self.idx = end + tag_length;
    }
    fn code_compound_from_idx(&self, idx: usize) -> Compound<'s> {
        Compound::new(&self.src, idx, self.src.len(), false, false, true)
    }
    fn parse_compounds(&mut self, stop_on_pipe: bool) -> Vec<Compound<'s>> {
        let mut compounds = Vec::new();
        let mut after_first_star = false;
        for (idx, char) in self.src.char_indices().skip(self.idx) {
            if self.code {
                // only one thing matters: whether we're closing the inline code
                if char == '`' {
                    self.close_compound(idx, 1, &mut compounds);
                    self.code = false;
                }
            } else if after_first_star {
                match char {
                    '*' => {
                        // this is the second star
                        self.close_compound(idx - 1, 2, &mut compounds);
                        self.bold ^= true;
                    }
                    '|' if stop_on_pipe => {
                        self.close_compound(idx - 1, 1, &mut compounds);
                        return compounds;
                    }
                    _ => {
                        // there was only one star
                        // Note that we don't handle a tag just after a star (execpt in code)
                        self.close_compound(idx - 1, 1, &mut compounds);
                        self.italic ^= true;
                    }
                }
                after_first_star = false;
            } else {
                match char {
                    '*' => {
                        after_first_star = true;
                        // we don't know yet if it's one or two stars
                    }
                    '|' if stop_on_pipe => {
                        self.close_compound(idx, 0, &mut compounds);
                        return compounds;
                    }
                    '`' => {
                        self.close_compound(idx, 1, &mut compounds);
                        self.code = true;
                    }
                    _ => {}
                }
            }
        }
        let mut idx = self.src.len();
        if after_first_star {
            idx -= 1;
        }
        self.close_compound(idx, 0, &mut compounds);
        compounds
    }
    fn parse_cells(&mut self) -> Vec<Composite<'s>> {
        let mut cells = Vec::new();
        while self.idx < self.src.len() {
            self.idx += 1;
            let style = if self.src[self.idx..].starts_with("* ") {
                self.idx += 2;
                CompositeStyle::ListItem
            } else {
                CompositeStyle::Paragraph
            };
            self.code = false;
            self.bold = false;
            self.italic = false;
            let compounds = self.parse_compounds(true);
            let mut composite = Composite { style, compounds };
            composite.trim_spaces();
            cells.push(composite);
        }
        if cells.len() > 0 && cells[cells.len()-1].compounds.len()==0 {
            cells.pop();
        }
        cells
    }
    pub fn inline(&mut self) -> Composite<'s> {
        assert_eq!(self.idx, 0, "A LineParser can only be consumed once");
        Composite {
            style: CompositeStyle::Paragraph,
            compounds: self.parse_compounds(false)
        }
    }
    pub fn line(&mut self) -> Line<'s> {
        assert_eq!(self.idx, 0, "A LineParser can only be consumed once");
        if self.src.starts_with("|") {
            let tr = TableRow {
                cells: self.parse_cells(),
            };
            return match tr.as_table_alignments() {
                Some(aligns) => Line::TableAlignments(aligns),
                None => Line::TableRow(tr),
            };
        }
        if self.src.starts_with("    ") {
            return Line::new_code(self.code_compound_from_idx(4));
        }
        if self.src.starts_with("\t") {
            return Line::new_code(self.code_compound_from_idx(1));
        }
        if self.src.starts_with("* ") {
            self.idx = 2;
            return Line::new_list_item(self.parse_compounds(false));
        }
        let header_level = header_level(self.src);
        if header_level > 0 {
            self.idx = header_level + 1;
            return Line::new_header(header_level as u8, self.parse_compounds(false));
        }
        Line::new_paragraph(self.parse_compounds(false))
    }
}

/// Tests of line parsing
#[cfg(test)]
mod tests {
    use crate::composite::*;
    use crate::compound::*;
    use crate::line::*;

    #[test]
    fn simple_line_parsing() {
        assert_eq!(
            Line::from("Hello **World**. *Code*: `sqrt(π/2)`"),
            Line::new_paragraph(vec![
                Compound::raw_str("Hello "),
                Compound::raw_str("World").bold(),
                Compound::raw_str(". "),
                Compound::raw_str("Code").italic(),
                Compound::raw_str(": "),
                Compound::raw_str("sqrt(π/2)").code(),
            ])
        );
    }

    #[test]
    fn nested_styles_parsing() {
        assert_eq!(
            Line::from("*Italic then **bold and italic `and some *code*`** and italic*"),
            Line::new_paragraph(vec![
                Compound::raw_str("Italic then ").italic(),
                Compound::raw_str("bold and italic ").bold().italic(),
                Compound::raw_str("and some *code*").bold().italic().code(),
                Compound::raw_str(" and italic").italic(),
            ])
        );
    }

    #[test]
    fn line_of_code() {
        assert_eq!(
            Line::from("    let r = Math.sin(π/2) * 7"),
            Line::new_code(Compound::raw_str("let r = Math.sin(π/2) * 7").code(),)
        );
    }

    #[test]
    fn standard_header() {
        assert_eq!(
            Line::from("### just a title"),
            Line::new_header(3, vec![Compound::raw_str("just a title"),])
        );
    }

    #[test]
    fn list_item() {
        assert_eq!(
            Line::from("* *list* item"),
            Line::new_list_item(vec![
                Compound::raw_str("list").italic(),
                Compound::raw_str(" item"),
            ])
        );
    }

    #[test]
    fn styled_header() {
        assert_eq!(
            Line::from("## a header with some **bold**!"),
            Line::new_header(
                2,
                vec![
                    Compound::raw_str("a header with some "),
                    Compound::raw_str("bold").bold(),
                    Compound::raw_str("!"),
                ]
            )
        );
    }

    #[test]
    fn table_row() {
        assert_eq!(
            Line::from("| bla |*italic*|hi!|"),
            Line::new_table_row(vec![
                Composite {
                    style: CompositeStyle::Paragraph,
                    compounds: vec![Compound::raw_str("bla"),],
                },
                Composite {
                    style: CompositeStyle::Paragraph,
                    compounds: vec![Compound::raw_str("italic").italic(),],
                },
                Composite {
                    style: CompositeStyle::Paragraph,
                    compounds: vec![Compound::raw_str("hi!"),],
                }
            ])
        );
    }

    #[test]
    fn table_alignments() {
        assert_eq!(
            Line::from("|-----|:--|:-:|----:"),
            Line::new_table_alignments(vec![
                Alignment::Unspecified,
                Alignment::Left,
                Alignment::Center,
                Alignment::Right,
            ])
        );
    }
}