use crate::ComponentStyle;

use chrono::{Datelike, Month};
use embedded_graphics::{
  mono_font::{
    ascii::{FONT_10X20, FONT_4X6, FONT_6X9, FONT_8X13},
    MonoFont, MonoTextStyle,
  },
  pixelcolor::{BinaryColor, PixelColor},
  prelude::*,
  primitives::{Line, PrimitiveStyle, Rectangle},
  text::Text,
};
use embedded_layout::prelude::*;
use num_traits::cast::FromPrimitive;

fn font(height: u32) -> MonoFont<'static> {
  if height < 8 {
    return FONT_4X6;
  } else if height < 10 {
    return FONT_6X9;
  } else if height < 14 {
    return FONT_8X13;
  } else {
    return FONT_10X20;
  }
}

pub struct CalendarDay<C> {
  pub top_left: Point,
  pub size: Size,
  pub fg_color: C,
  pub bg_color: C,
  pub border: u32,
  pub day_of_month: u32,
  pub has_event: bool,
}

impl<C> Drawable for CalendarDay<C>
where
  C: PixelColor + From<BinaryColor>,
{
  type Color = C;
  type Output = ();

  fn draw<D>(&self, target: &mut D) -> Result<Self::Output, D::Error>
  where
    D: DrawTarget<Color = C>,
  {
    // Adding based on border so that the borders overlap
    let date_rect = Rectangle::new(
      self.top_left,
      self.size + Size::new(self.border / 2 + 1, self.border / 2 + 1),
    );
    date_rect
      .into_styled(PrimitiveStyle::with_fill(self.bg_color))
      .draw(target)?;
    date_rect
      .into_styled(PrimitiveStyle::with_stroke(self.fg_color, self.border))
      .draw(target)?;

    let text = format!("{}", self.day_of_month);
    let date_font = font(self.size.height / 2);
    let text_style = MonoTextStyle::new(&date_font, self.fg_color);
    Text::new(&text, self.top_left, text_style)
      .align_to(&date_rect, horizontal::Center, vertical::Center)
      .draw(target)?;

    if self.has_event {
      let event_padding: i32 = 2 + self.size.height as i32 / 10;
      Line::new(
        self.top_left + Point::new(event_padding, self.size.height as i32 - event_padding),
        self.top_left
          + Point::new(
            self.size.width as i32 - event_padding,
            self.size.height as i32 - event_padding,
          ),
      )
      .into_styled(PrimitiveStyle::with_stroke(self.fg_color, 2))
      .draw(target)?;
    }

    Ok(())
  }
}

pub struct CalendarMonth<C> {
  pub top_left: Point,
  pub size: Size,
  pub border: u32,
  pub fg_color: C,
  pub bg_color: C,
  pub month: chrono::Month,
}

impl<C> Drawable for CalendarMonth<C>
where
  C: PixelColor + From<BinaryColor>,
{
  type Color = C;
  type Output = ();

  fn draw<D>(&self, target: &mut D) -> Result<Self::Output, D::Error>
  where
    D: DrawTarget<Color = C>,
  {
    let rect = Rectangle::new(
      self.top_left,
      self.size + Size::new(self.border / 2 + 1, self.border / 2 + 1),
    );
    rect
      .into_styled(PrimitiveStyle::with_stroke(self.fg_color, self.border))
      .draw(target)?;

    let month_font = font((self.size.height as f32 * 0.8 - 2.) as u32);
    let text_style = MonoTextStyle::new(&month_font, self.fg_color);
    Text::new(self.month.name(), self.top_left, text_style)
      .align_to(&rect, horizontal::Center, vertical::Center)
      .draw(target)?;

    Ok(())
  }
}

pub struct Calendar<C> {
  pub top_left: Point,
  pub size: Size,
  pub border: u32,
  pub fg_color: C,
  pub bg_color: C,
  // If hi_color is None, the fg and bg colors are inverted instead.
  pub hi_color: Option<C>,
}

impl<C> Drawable for Calendar<C>
where
  C: PixelColor + From<BinaryColor>,
{
  type Color = C;
  type Output = ();

  fn draw<D>(&self, target: &mut D) -> Result<Self::Output, D::Error>
  where
    D: DrawTarget<Color = C>,
  {
    let border = self.border;

    let date_now = chrono::offset::Local::now().date();
    let first_day = date_now.with_day(1).unwrap();
    let last_day = date_now
      .with_day(1)
      .unwrap()
      .with_month(date_now.month() % 11 + 1)
      .unwrap()
      .pred();

    let empty_squares = first_day.weekday().num_days_from_monday();
    let squares_needed = empty_squares + last_day.day();
    let month_needs_separate_row = empty_squares < 4;
    let mut rows_needed = squares_needed / 7 + 1;
    if month_needs_separate_row {
      rows_needed += 1;
    }

    let width = self.size.width / 7;
    let height = self.size.height / rows_needed;

    let month_width = if month_needs_separate_row {
      width * 7
    } else {
      width * empty_squares
    };
    let calendar_month = CalendarMonth {
      border,
      top_left: self.top_left,
      size: Size::new(month_width, height),
      fg_color: self.fg_color,
      bg_color: self.bg_color,
      month: Month::from_u32(date_now.month()).unwrap(),
    };
    calendar_month.draw(target)?;

    for i in empty_squares..squares_needed {
      let x = i % 7;
      let mut y = i / 7;
      if month_needs_separate_row {
        y = y + 1;
      }
      let day_of_month = i - empty_squares + 1;
      let is_weekend = date_now
        .with_day(day_of_month)
        .unwrap()
        .weekday()
        .num_days_from_monday()
        >= 5;
      let is_today = day_of_month == date_now.day();

      let (mut fg_color, mut bg_color, mut border) = match is_weekend ^ is_today {
        false => (self.fg_color, self.bg_color, border),
        true => (self.bg_color, self.fg_color, 0),
      };
      if is_today && self.hi_color.is_some() {
        (fg_color, bg_color, border) = (self.bg_color, self.hi_color.unwrap(), 0);
      }

      let calendar_day = CalendarDay {
        border,
        top_left: self.top_left + Point::new((width * x) as i32, (height * y) as i32),
        size: Size::new(width, height),
        fg_color,
        bg_color,
        day_of_month: i - empty_squares + 1,
        has_event: i - empty_squares + 1 == date_now.day(),
      };
      calendar_day.draw(target)?;
    }

    Ok(())
  }
}

pub struct ScrollingWeek {
  day: chrono::NaiveDate,
}

impl ScrollingWeek {
  pub fn succ(&self) -> ScrollingWeek {
    let start_of_next_month = self
      .day
      .with_month(self.day.month() % 11 + 1)
      .unwrap()
      .with_day(1)
      .unwrap();

    let days_until_next_month =
      start_of_next_month.num_days_from_ce() - self.day.num_days_from_ce();
    let day_of_week = self.day.weekday().number_from_monday() as i32;

    let days_to_skip = if days_until_next_month < 7 {
      days_until_next_month
    } else {
      8 - day_of_week
    };

    ScrollingWeek {
      day: self
        .day
        .checked_add_signed(chrono::Duration::days(days_to_skip as i64))
        .unwrap(),
    }
  }

  pub fn month(&self) -> chrono::Month {
    chrono::Month::from_u32(self.day.month()).unwrap()
  }

  pub fn week(&self) -> u32 {
    self.day.iso_week().week()
  }

  pub fn year(&self) -> i32 {
    self.day.year()
  }
}

pub struct ScrollingCalendar<C> {
  pub top_left: Point,
  pub size: Size,
  pub style: ComponentStyle<C>,
  pub day: chrono::NaiveDate,
  pub weeks: u32,
}

impl<C> Drawable for ScrollingCalendar<C>
where
  C: PixelColor + From<BinaryColor>,
{
  type Color = C;
  type Output = ();

  fn draw<D>(&self, target: &mut D) -> Result<Self::Output, D::Error>
  where
    D: DrawTarget<Color = C>,
  {
    let height = self.size.height / (1 + self.weeks * 2);
    let mut week = ScrollingWeek {
      day: chrono::NaiveDate::from_isoywd(
        self.day.year(),
        self.day.iso_week().week(),
        chrono::Weekday::Mon,
      ),
    };

    for i in 0..self.weeks * 2 {
      week = week.succ();

      let calendar_week = CalendarWeek {
        top_left: Point::new(self.top_left.x, self.top_left.y + (height * i) as i32),
        size: Size::new(self.size.width, height),
        style: self.style.clone(),
        year: week.year(),
        month: week.month(),
        week: week.week(),
      };
      calendar_week.draw(target)?;
    }

    Ok(())
  }
}

pub struct CalendarWeek<C> {
  pub top_left: Point,
  pub size: Size,
  pub style: ComponentStyle<C>,
  pub year: i32,
  pub month: chrono::Month,
  pub week: u32,
}

impl<C> Drawable for CalendarWeek<C>
where
  C: PixelColor + From<BinaryColor>,
{
  type Color = C;
  type Output = ();

  fn draw<D>(&self, target: &mut D) -> Result<Self::Output, D::Error>
  where
    D: DrawTarget<Color = C>,
  {
    let monday = chrono::NaiveDate::from_isoywd(self.year, self.week, chrono::Weekday::Mon);
    let sunday = chrono::NaiveDate::from_isoywd(self.year, self.week, chrono::Weekday::Sun);
    let week_starts_in_prev_month = monday.month() != self.month.number_from_month();
    let week_ends_in_next_month = sunday.month() != self.month.number_from_month();
    let first_day = match week_starts_in_prev_month {
      true => sunday.with_day(1).unwrap(),
      false => monday,
    };
    let last_day = match week_ends_in_next_month {
      true => sunday.with_day(1).unwrap().pred(),
      false => sunday,
    };

    let width = self.size.width / 7;

    let mut weekday = first_day.weekday();
    for i in first_day.weekday().number_from_monday()..(last_day.weekday().number_from_monday() + 1)
    {
      let day = chrono::NaiveDate::from_isoywd(self.year, self.week, weekday);

      let (fg_color, bg_color) = match weekday.num_days_from_monday() < 5 {
        true => (self.style.fg_color, self.style.bg_color),
        false => (self.style.bg_color, self.style.fg_color),
      };

      let style = ComponentStyle {
        fg_color,
        bg_color,
        ..self.style
      };

      let calendar_day = CalendarDay {
        top_left: self.top_left + Point::new((width * weekday.num_days_from_monday()) as i32, 0),
        size: Size::new(width, self.size.height),
        border: self.style.border,
        fg_color,
        bg_color,
        day_of_month: day.day(),
        has_event: true,
      };
      calendar_day.draw(target)?;

      weekday = weekday.succ();
    }

    Ok(())
  }
}