use crate::term::BufWrite as _;
use std::convert::TryInto as _;

#[derive(Clone, Debug)]
pub struct Grid {
    size: Size,
    pos: Pos,
    saved_pos: Pos,
    rows: Vec<crate::row::Row>,
    scroll_top: u16,
    scroll_bottom: u16,
    origin_mode: bool,
    saved_origin_mode: bool,
    scrollback: std::collections::VecDeque<crate::row::Row>,
    scrollback_len: usize,
    scrollback_offset: usize,
}

impl Grid {
    pub fn new(size: Size, scrollback_len: usize) -> Self {
        Self {
            size,
            pos: Pos::default(),
            saved_pos: Pos::default(),
            rows: vec![crate::row::Row::new(size.cols); size.rows as usize],
            scroll_top: 0,
            scroll_bottom: size.rows - 1,
            origin_mode: false,
            saved_origin_mode: false,
            scrollback: std::collections::VecDeque::new(),
            scrollback_len,
            scrollback_offset: 0,
        }
    }

    fn new_row(&self) -> crate::row::Row {
        crate::row::Row::new(self.size.cols)
    }

    pub fn clear(&mut self) {
        self.pos = Pos::default();
        self.saved_pos = Pos::default();
        for row in self.drawing_rows_mut() {
            row.clear(crate::attrs::Attrs::default());
        }
        self.scroll_top = 0;
        self.scroll_bottom = self.size.rows - 1;
        self.origin_mode = false;
        self.saved_origin_mode = false;
    }

    pub fn size(&self) -> Size {
        self.size
    }

    pub fn set_size(&mut self, size: Size) {
        if size.cols != self.size.cols {
            for row in &mut self.rows {
                row.wrap(false);
            }
        }

        if self.scroll_bottom == self.size.rows - 1 {
            self.scroll_bottom = size.rows - 1;
        }

        self.size = size;
        for row in &mut self.rows {
            row.resize(size.cols as usize, crate::cell::Cell::default());
        }
        self.rows.resize(size.rows as usize, self.new_row());

        if self.scroll_bottom >= size.rows {
            self.scroll_bottom = size.rows - 1;
        }
        if self.scroll_bottom < self.scroll_top {
            self.scroll_top = 0;
        }

        self.row_clamp_top(false);
        self.row_clamp_bottom(false);
        self.col_clamp();
    }

    pub fn pos(&self) -> Pos {
        self.pos
    }

    pub fn set_pos(&mut self, mut pos: Pos) {
        if self.origin_mode {
            pos.row = pos.row.saturating_add(self.scroll_top);
        }
        self.pos = pos;
        self.row_clamp_top(self.origin_mode);
        self.row_clamp_bottom(self.origin_mode);
        self.col_clamp();
    }

    pub fn save_cursor(&mut self) {
        self.saved_pos = self.pos;
        self.saved_origin_mode = self.origin_mode;
    }

    pub fn restore_cursor(&mut self) {
        self.pos = self.saved_pos;
        self.origin_mode = self.saved_origin_mode;
    }

    pub fn visible_rows(&self) -> impl Iterator<Item = &crate::row::Row> {
        let scrollback_len = self.scrollback.len();
        let rows_len = self.rows.len();
        self.scrollback
            .iter()
            .skip(scrollback_len - self.scrollback_offset)
            .chain(self.rows.iter().take(rows_len - self.scrollback_offset))
    }

    pub fn drawing_rows(&self) -> impl Iterator<Item = &crate::row::Row> {
        self.rows.iter()
    }

    pub fn drawing_rows_mut(
        &mut self,
    ) -> impl Iterator<Item = &mut crate::row::Row> {
        self.rows.iter_mut()
    }

    pub fn visible_row(&self, pos: Pos) -> Option<&crate::row::Row> {
        self.visible_rows().nth(pos.row as usize)
    }

    pub fn drawing_row(&self, pos: Pos) -> Option<&crate::row::Row> {
        self.drawing_rows().nth(pos.row as usize)
    }

    pub fn drawing_row_mut(
        &mut self,
        pos: Pos,
    ) -> Option<&mut crate::row::Row> {
        self.drawing_rows_mut().nth(pos.row as usize)
    }

    pub fn current_row_mut(&mut self) -> &mut crate::row::Row {
        self.drawing_row_mut(self.pos)
            .expect("cursor not pointing to a cell")
    }

    pub fn visible_cell(&self, pos: Pos) -> Option<&crate::cell::Cell> {
        self.visible_row(pos).and_then(|r| r.get(pos.col))
    }

    pub fn drawing_cell(&self, pos: Pos) -> Option<&crate::cell::Cell> {
        self.drawing_row(pos).and_then(|r| r.get(pos.col))
    }

    pub fn drawing_cell_mut(
        &mut self,
        pos: Pos,
    ) -> Option<&mut crate::cell::Cell> {
        self.drawing_row_mut(pos).and_then(|r| r.get_mut(pos.col))
    }

    pub fn current_cell(&self) -> &crate::cell::Cell {
        self.drawing_cell(self.pos)
            .expect("cursor not pointing to a cell")
    }

    pub fn current_cell_mut(&mut self) -> &mut crate::cell::Cell {
        self.drawing_cell_mut(self.pos)
            .expect("cursor not pointing to a cell")
    }

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

    pub fn scrollback(&self) -> usize {
        self.scrollback_offset
    }

    pub fn set_scrollback(&mut self, rows: usize) {
        self.scrollback_offset = rows.min(self.scrollback.len());
    }

    pub fn write_contents(&self, contents: &mut String) {
        let mut wrapping = false;
        for row in self.visible_rows() {
            row.write_contents(contents, 0, self.size.cols, wrapping);
            if !row.wrapped() {
                contents.push_str("\n");
            }
            wrapping = row.wrapped();
        }

        while contents.ends_with('\n') {
            contents.truncate(contents.len() - 1);
        }
    }

    pub fn write_contents_formatted(
        &self,
        contents: &mut Vec<u8>,
    ) -> crate::attrs::Attrs {
        crate::term::ClearAttrs::default().write_buf(contents);
        crate::term::ClearScreen::default().write_buf(contents);

        let mut prev_attrs = crate::attrs::Attrs::default();
        let mut prev_pos = Pos::default();
        let mut wrapping = false;
        for (i, row) in self.visible_rows().enumerate() {
            let i = i.try_into().unwrap();
            let (new_pos, new_attrs) = row.write_contents_formatted(
                contents,
                0,
                self.size.cols,
                i,
                wrapping,
                prev_pos,
                prev_attrs,
            );
            prev_pos = new_pos;
            prev_attrs = new_attrs;
            wrapping = row.wrapped();
        }

        // writing a character to the last column of a row doesn't wrap the
        // cursor immediately - it waits until the next character is actually
        // drawn. it is only possible for the cursor to have this kind of
        // position after drawing a character though, so if we end in this
        // position, we need to redraw the character at the end of the row.
        if prev_pos != self.pos && self.pos.col >= self.size.cols {
            let mut pos = Pos {
                row: self.pos.row,
                col: self.size.cols - 1,
            };
            if self.visible_cell(pos).unwrap().is_wide_continuation() {
                pos.col = self.size.cols - 2;
            }
            let cell = self.visible_cell(pos).unwrap();
            if cell.has_contents() {
                crate::term::MoveFromTo::new(prev_pos, pos)
                    .write_buf(contents);
                contents.extend(cell.contents().as_bytes());
            } else {
                // if the cell doesn't have contents, we can't have gotten
                // here by drawing a character in the last column. this means
                // that as far as i'm aware, we have to have reached here from
                // a newline when we were already after the end of an earlier
                // row. in the case where we are already after the end of an
                // earlier row, we can just write a few newlines, otherwise we
                // also need to do the same as above to get ourselves to after
                // the end of a row.
                let orig_row = pos.row;
                let mut found = false;
                for i in (0..orig_row).rev() {
                    pos.row = i;
                    pos.col = self.size.cols - 1;
                    if self.visible_cell(pos).unwrap().is_wide_continuation()
                    {
                        pos.col = self.size.cols - 2;
                    }
                    let cell = self.visible_cell(pos).unwrap();
                    if cell.has_contents() {
                        if prev_pos.row != i || prev_pos.col < self.size.cols
                        {
                            crate::term::MoveFromTo::new(prev_pos, pos)
                                .write_buf(contents);
                            contents.extend(cell.contents().as_bytes());
                        }
                        contents.extend(
                            "\n".repeat((orig_row - i) as usize).as_bytes(),
                        );
                        found = true;
                        break;
                    }
                }

                // this can happen if you get the cursor off the end of a row,
                // and then do something to clear the end of the current row
                // without moving the cursor (IL, DL, ED, EL, etc). we know
                // there can't be something in the last column because we
                // would have caught that above, so it should be safe to
                // overwrite it.
                if !found {
                    pos.row = orig_row;
                    crate::term::MoveFromTo::new(prev_pos, pos)
                        .write_buf(contents);
                    contents.push(b' ');
                    crate::term::SaveCursor::default().write_buf(contents);
                    crate::term::Backspace::default().write_buf(contents);
                    crate::term::EraseChar::new(1).write_buf(contents);
                    crate::term::RestoreCursor::default().write_buf(contents);
                }
            }
        } else {
            crate::term::MoveFromTo::new(prev_pos, self.pos)
                .write_buf(contents);
        }

        prev_attrs
    }

    pub fn write_contents_diff(
        &self,
        contents: &mut Vec<u8>,
        prev: &Self,
        mut prev_attrs: crate::attrs::Attrs,
    ) -> crate::attrs::Attrs {
        let mut prev_pos = prev.pos;
        let mut wrapping = false;
        for (i, (row, prev_row)) in
            self.visible_rows().zip(prev.visible_rows()).enumerate()
        {
            let i = i.try_into().unwrap();
            let (new_pos, new_attrs) = row.write_contents_diff(
                contents,
                prev_row,
                0,
                self.size.cols,
                i,
                wrapping,
                prev_pos,
                prev_attrs,
            );
            prev_pos = new_pos;
            prev_attrs = new_attrs;
            wrapping = row.wrapped();
        }

        // writing a character to the last column of a row doesn't wrap the
        // cursor immediately - it waits until the next character is actually
        // drawn. it is only possible for the cursor to have this kind of
        // position after drawing a character though, so if we end in this
        // position, we need to redraw the character at the end of the row.
        if prev_pos != self.pos && self.pos.col >= self.size.cols {
            let mut pos = Pos {
                row: self.pos.row,
                col: self.size.cols - 1,
            };
            if self.visible_cell(pos).unwrap().is_wide_continuation() {
                pos.col = self.size.cols - 2;
            }
            let cell = self.visible_cell(pos).unwrap();
            if cell.has_contents() {
                crate::term::MoveFromTo::new(prev_pos, pos)
                    .write_buf(contents);
                contents.extend(cell.contents().as_bytes());
            } else {
                // if the cell doesn't have contents, we can't have gotten
                // here by drawing a character in the last column. this means
                // that as far as i'm aware, we have to have reached here from
                // a newline when we were already after the end of an earlier
                // row. in the case where we are already after the end of an
                // earlier row, we can just write a few newlines, otherwise we
                // also need to do the same as above to get ourselves to after
                // the end of a row.
                let orig_row = pos.row;
                let mut found = false;
                for i in (0..orig_row).rev() {
                    pos.row = i;
                    pos.col = self.size.cols - 1;
                    if self.visible_cell(pos).unwrap().is_wide_continuation()
                    {
                        pos.col = self.size.cols - 2;
                    }
                    let cell = self.visible_cell(pos).unwrap();
                    if cell.has_contents() {
                        if prev_pos.row != i || prev_pos.col < self.size.cols
                        {
                            crate::term::MoveFromTo::new(prev_pos, pos)
                                .write_buf(contents);
                            contents.extend(cell.contents().as_bytes());
                        }
                        contents.extend(
                            "\n".repeat((orig_row - i) as usize).as_bytes(),
                        );
                        found = true;
                        break;
                    }
                }

                // this can happen if you get the cursor off the end of a row,
                // and then do something to clear the end of the current row
                // without moving the cursor (IL, DL, ED, EL, etc). we know
                // there can't be something in the last column because we
                // would have caught that above, so it should be safe to
                // overwrite it.
                if !found {
                    pos.row = orig_row;
                    crate::term::MoveFromTo::new(prev_pos, pos)
                        .write_buf(contents);
                    contents.push(b' ');
                    crate::term::SaveCursor::default().write_buf(contents);
                    crate::term::Backspace::default().write_buf(contents);
                    crate::term::EraseChar::new(1).write_buf(contents);
                    crate::term::RestoreCursor::default().write_buf(contents);
                }
            }
        } else {
            crate::term::MoveFromTo::new(prev_pos, self.pos)
                .write_buf(contents);
        }

        prev_attrs
    }

    pub fn erase_all(&mut self, attrs: crate::attrs::Attrs) {
        for row in self.drawing_rows_mut() {
            row.clear(attrs);
        }
    }

    pub fn erase_all_forward(&mut self, attrs: crate::attrs::Attrs) {
        let pos = self.pos;
        for row in self.drawing_rows_mut().skip(pos.row as usize + 1) {
            row.clear(attrs);
        }

        self.erase_row_forward(attrs);
    }

    pub fn erase_all_backward(&mut self, attrs: crate::attrs::Attrs) {
        let pos = self.pos;
        for row in self.drawing_rows_mut().take(pos.row as usize) {
            row.clear(attrs);
        }

        self.erase_row_backward(attrs);
    }

    pub fn erase_row(&mut self, attrs: crate::attrs::Attrs) {
        self.current_row_mut().clear(attrs);
    }

    pub fn erase_row_forward(&mut self, attrs: crate::attrs::Attrs) {
        let size = self.size;
        let pos = self.pos;
        let row = self.current_row_mut();
        for col in pos.col..size.cols {
            row.erase(col as usize, attrs);
        }
    }

    pub fn erase_row_backward(&mut self, attrs: crate::attrs::Attrs) {
        let size = self.size;
        let pos = self.pos;
        let row = self.current_row_mut();
        for col in 0..=pos.col.min(size.cols - 1) {
            row.erase(col as usize, attrs);
        }
    }

    pub fn insert_cells(&mut self, count: u16) {
        let size = self.size;
        let pos = self.pos;
        let wide =
            pos.col < size.cols && self.current_cell().is_wide_continuation();
        let row = self.current_row_mut();
        for _ in 0..count {
            if wide {
                row.get_mut(pos.col).unwrap().set_wide_continuation(false);
            }
            row.insert(pos.col as usize, crate::cell::Cell::default());
            if wide {
                row.get_mut(pos.col).unwrap().set_wide_continuation(true);
            }
        }
        row.truncate(size.cols as usize);
    }

    pub fn delete_cells(&mut self, count: u16) {
        let size = self.size;
        let pos = self.pos;
        let row = self.current_row_mut();
        for _ in 0..(count.min(size.cols - pos.col)) {
            row.remove(pos.col as usize);
        }
        row.resize(size.cols as usize, crate::cell::Cell::default());
    }

    pub fn erase_cells(&mut self, count: u16, attrs: crate::attrs::Attrs) {
        let size = self.size;
        let pos = self.pos;
        let row = self.current_row_mut();
        for col in pos.col..((pos.col + count).min(size.cols)) {
            row.clear_wide(col);
            row.erase(col as usize, attrs);
        }
    }

    pub fn insert_lines(&mut self, count: u16) {
        for _ in 0..count {
            self.rows.remove(self.scroll_bottom as usize);
            self.rows.insert(self.pos.row as usize, self.new_row());
        }
    }

    pub fn delete_lines(&mut self, count: u16) {
        for _ in 0..(count.min(self.size.rows - self.pos.row)) {
            self.rows
                .insert(self.scroll_bottom as usize + 1, self.new_row());
            self.rows.remove(self.pos.row as usize);
        }
    }

    pub fn scroll_up(&mut self, count: u16) {
        for _ in 0..(count.min(self.size.rows - self.scroll_top)) {
            self.rows
                .insert(self.scroll_bottom as usize + 1, self.new_row());
            let removed = self.rows.remove(self.scroll_top as usize);
            if self.scrollback_len > 0 && !self.scroll_region_active() {
                self.scrollback.push_back(removed);
                while self.scrollback.len() > self.scrollback_len {
                    self.scrollback.pop_front();
                }
                if self.scrollback_offset > 0 {
                    self.scrollback_offset =
                        self.scrollback.len().min(self.scrollback_offset + 1);
                }
            }
        }
    }

    pub fn scroll_down(&mut self, count: u16) {
        for _ in 0..count {
            self.rows.remove(self.scroll_bottom as usize);
            self.rows.insert(self.scroll_top as usize, self.new_row());
        }
    }

    pub fn set_scroll_region(&mut self, top: u16, bottom: u16) {
        let bottom = bottom.min(self.size().rows - 1);
        if top < bottom {
            self.scroll_top = top;
            self.scroll_bottom = bottom;
        } else {
            self.scroll_top = 0;
            self.scroll_bottom = self.size().rows - 1;
        }
        self.pos.row = self.scroll_top;
        self.pos.col = 0;
    }

    fn in_scroll_region(&self) -> bool {
        self.pos.row >= self.scroll_top && self.pos.row <= self.scroll_bottom
    }

    fn scroll_region_active(&self) -> bool {
        self.scroll_top != 0 || self.scroll_bottom != self.size.rows - 1
    }

    pub fn set_origin_mode(&mut self, mode: bool) {
        self.origin_mode = mode;
        self.set_pos(Pos { row: 0, col: 0 })
    }

    pub fn row_inc_clamp(&mut self, count: u16) {
        let in_scroll_region = self.in_scroll_region();
        self.pos.row = self.pos.row.saturating_add(count);
        self.row_clamp_bottom(in_scroll_region);
    }

    pub fn row_inc_scroll(&mut self, count: u16) {
        let in_scroll_region = self.in_scroll_region();
        self.pos.row = self.pos.row.saturating_add(count);
        let lines = self.row_clamp_bottom(in_scroll_region);
        self.scroll_up(lines);
    }

    pub fn row_dec_clamp(&mut self, count: u16) {
        let in_scroll_region = self.in_scroll_region();
        self.pos.row = self.pos.row.saturating_sub(count);
        self.row_clamp_top(in_scroll_region);
    }

    pub fn row_dec_scroll(&mut self, count: u16) {
        let in_scroll_region = self.in_scroll_region();
        // need to account for clamping by both row_clamp_top and by
        // saturating_sub
        let extra_lines = if count > self.pos.row {
            count - self.pos.row
        } else {
            0
        };
        self.pos.row = self.pos.row.saturating_sub(count);
        let lines = self.row_clamp_top(in_scroll_region);
        self.scroll_down(lines + extra_lines);
    }

    pub fn row_set(&mut self, i: u16) {
        self.pos.row = i;
    }

    pub fn col_inc(&mut self, count: u16) {
        self.pos.col = self.pos.col.saturating_add(count);
    }

    pub fn col_inc_clamp(&mut self, count: u16) {
        self.pos.col = self.pos.col.saturating_add(count);
        self.col_clamp();
    }

    pub fn col_dec(&mut self, count: u16) {
        self.pos.col = self.pos.col.saturating_sub(count);
    }

    pub fn col_tab(&mut self) {
        self.pos.col -= self.pos.col % 8;
        self.pos.col += 8;
        self.col_clamp();
    }

    pub fn col_set(&mut self, i: u16) {
        self.pos.col = i;
        self.col_clamp();
    }

    pub fn col_wrap(&mut self, width: u16, wrap: bool) {
        if self.pos.col > self.size.cols - width {
            self.current_row_mut().wrap(wrap);
            self.pos.col = 0;
            self.row_inc_scroll(1);
        }
    }

    fn row_clamp_top(&mut self, limit_to_scroll_region: bool) -> u16 {
        if limit_to_scroll_region && self.pos.row < self.scroll_top {
            let rows = self.scroll_top - self.pos.row;
            self.pos.row = self.scroll_top;
            rows
        } else {
            0
        }
    }

    fn row_clamp_bottom(&mut self, limit_to_scroll_region: bool) -> u16 {
        let bottom = if limit_to_scroll_region {
            self.scroll_bottom
        } else {
            self.size.rows - 1
        };
        if self.pos.row > bottom {
            let rows = self.pos.row - bottom;
            self.pos.row = bottom;
            rows
        } else {
            0
        }
    }

    fn col_clamp(&mut self) {
        if self.pos.col > self.size.cols - 1 {
            self.pos.col = self.size.cols - 1;
        }
    }
}

#[derive(Copy, Clone, Debug, Default, Eq, PartialEq)]
pub struct Size {
    pub rows: u16,
    pub cols: u16,
}

#[derive(Copy, Clone, Debug, Default, Eq, PartialEq)]
pub struct Pos {
    pub row: u16,
    pub col: u16,
}