use std::rc::Rc;

mod rope;
use rope::Rope;
pub use rope::{CharIterator, CharWithPointIterator};

mod reader;
pub use reader::TextBufferReader;

mod writer;
pub use writer::TextBufferWriter;

/// A block of text, usually containing the contents of a text file.
#[derive(Clone)]
pub struct TextBuffer {
    contents: Rc<Rope>,
}

/// A location in a [TextBuffer]
#[derive(Clone, Copy, Debug, Default, PartialEq)]
pub enum Point {
    /// The end of the buffer
    #[default]
    Start,
    LineColumn(usize, usize),
    End,
}

impl TextBuffer {
    /// Create a new empty [TextBuffer]
    pub fn new() -> Self {
        Self {
            contents: Rope::empty(),
        }
    }

    /// The size of the contents in bytes
    pub fn num_bytes(&self) -> usize {
        self.contents.total_bytes()
    }

    /// The size of the contents in characters
    pub fn num_chars(&self) -> usize {
        self.contents.total_chars()
    }

    /// The total number of lines in the contents
    pub fn num_lines(&self) -> usize {
        let num_chars = self.num_chars();
        if num_chars == 0 {
            0
        } else {
            self.contents.total_lines()
        }
    }

    /// Insert `text` at `point`.
    pub fn insert_text(&mut self, text: impl Into<String>, point: Point) {
        match point {
            Point::Start => {
                self.contents = self.contents.insert_at_char_index(0, text);
            }
            Point::LineColumn(_, _) => {
                todo!()
            }
            Point::End => {
                self.contents = self
                    .contents
                    .insert_at_char_index(self.contents.total_chars(), text);
            }
        }
    }

    pub fn insert_char(&self, c: char, point: Point) -> Self {
        let contents = match point {
            Point::Start => self.contents.insert_at_char_index(0, c),
            Point::LineColumn(line_num, column_num) => {
                self.contents
                    .insert_at_line_and_column(line_num - 1, column_num, c)
            }
            Point::End => self
                .contents
                .insert_at_char_index(self.contents.total_chars(), c),
        };
        Self { contents }
    }

    pub fn delete_at_char_index(&mut self, start: usize, length: usize) -> bool {
        match self.contents.delete_at_char_index(start, length) {
            Ok(r) => {
                self.contents = r;
                true
            }
            Err(_) => false,
        }
    }

    pub fn iter_chars(&self) -> CharIterator {
        self.contents.iter_chars()
    }

    pub fn iter_chars_with_point(&self) -> CharWithPointIterator {
        self.contents.iter_chars_with_point()
    }
}

impl Default for TextBuffer {
    fn default() -> Self {
        Self::new()
    }
}

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

    #[test]
    fn new_creates_empty_buffer() {
        let target = TextBuffer::new();
        assert_eq!(0, target.num_bytes());
        assert_eq!(0, target.num_chars());
        assert_eq!(0, target.num_lines());
    }

    #[test]
    fn insert_char_at_end_increases_counts_as_expected() {
        let target = TextBuffer::new();
        let target = target.insert_char('A', Point::End);
        assert_eq!(1, target.num_bytes());
        assert_eq!(1, target.num_chars());
        assert_eq!(1, target.num_lines());
        let target = target.insert_char(' ', Point::End);
        assert_eq!(2, target.num_bytes());
        assert_eq!(2, target.num_chars());
        assert_eq!(1, target.num_lines());
        let target = target.insert_char('c', Point::End);
        assert_eq!(3, target.num_bytes());
        assert_eq!(3, target.num_chars());
        assert_eq!(1, target.num_lines());
        let target = target.insert_char('a', Point::End);
        assert_eq!(4, target.num_bytes());
        assert_eq!(4, target.num_chars());
        assert_eq!(1, target.num_lines());
        let target = target.insert_char('t', Point::End);
        assert_eq!(5, target.num_bytes());
        assert_eq!(5, target.num_chars());
        assert_eq!(1, target.num_lines());
        let target = target.insert_char('\n', Point::End);
        assert_eq!(6, target.num_bytes());
        assert_eq!(6, target.num_chars());
        assert_eq!(1, target.num_lines());
        let target = target.insert_char('A', Point::End);
        assert_eq!(7, target.num_bytes());
        assert_eq!(7, target.num_chars());
        assert_eq!(2, target.num_lines());
        let target = target.insert_char('\n', Point::End);
        assert_eq!(8, target.num_bytes());
        assert_eq!(8, target.num_chars());
        assert_eq!(2, target.num_lines());
        let target = target.insert_char('\n', Point::End);
        assert_eq!(9, target.num_bytes());
        assert_eq!(9, target.num_chars());
        assert_eq!(3, target.num_lines());
        let target = target.insert_char('*', Point::End);
        assert_eq!(10, target.num_bytes());
        assert_eq!(10, target.num_chars());
        assert_eq!(4, target.num_lines());
        let target = target.insert_char('*', Point::End);
        assert_eq!(11, target.num_bytes());
        assert_eq!(11, target.num_chars());
        assert_eq!(4, target.num_lines());
        let target = target.insert_char(' ', Point::End);
        assert_eq!(12, target.num_bytes());
        assert_eq!(12, target.num_chars());
        assert_eq!(4, target.num_lines());
        let target = target.insert_char('猫', Point::End);
        assert_eq!(15, target.num_bytes());
        assert_eq!(13, target.num_chars());
        assert_eq!(4, target.num_lines());
        let target = target.insert_char(' ', Point::End);
        assert_eq!(16, target.num_bytes());
        assert_eq!(14, target.num_chars());
        assert_eq!(4, target.num_lines());
        let target = target.insert_char('\n', Point::End);
        assert_eq!(17, target.num_bytes());
        assert_eq!(15, target.num_chars());
        assert_eq!(4, target.num_lines());
        let target = target.insert_char('_', Point::End);
        assert_eq!(18, target.num_bytes());
        assert_eq!(16, target.num_chars());
        assert_eq!(5, target.num_lines());
    }

    #[test]
    fn insert_text_at_end_increases_counts_as_expected() {
        let mut target = TextBuffer::new();
        target.insert_text("The", Point::End);
        assert_eq!(3, target.num_bytes());
        assert_eq!(3, target.num_chars());
        assert_eq!(1, target.num_lines());
        target.insert_text(" ", Point::End);
        assert_eq!(4, target.num_bytes());
        assert_eq!(4, target.num_chars());
        assert_eq!(1, target.num_lines());
        target.insert_text("quick brown", Point::End);
        assert_eq!(15, target.num_bytes());
        assert_eq!(15, target.num_chars());
        assert_eq!(1, target.num_lines());
        target.insert_text(" fox\n", Point::End);
        assert_eq!(20, target.num_bytes());
        assert_eq!(20, target.num_chars());
        assert_eq!(1, target.num_lines());
        target.insert_text("jumps over the lazy 猫.", Point::End);
        assert_eq!(44, target.num_bytes());
        assert_eq!(42, target.num_chars());
        assert_eq!(2, target.num_lines());
    }
}