use std::fmt;
use std::io;
use std::io::Write;

use crossterm::Command;
use crossterm::queue;
use crossterm::style::Attribute as CAttribute;
use crossterm::style::Color as CColor;
use crossterm::style::Colors;
use crossterm::style::Print;
use crossterm::style::SetAttribute;
use crossterm::style::SetBackgroundColor;
use crossterm::style::SetColors;
use crossterm::style::SetForegroundColor;
use ratatui::style::Color;
use ratatui::style::Modifier;
use ratatui::text::Span;

#[derive(Debug, Clone, PartialEq, Eq)]
pub struct SetScrollRegion(pub std::ops::Range<u16>);

impl Command for SetScrollRegion {
    fn write_ansi(&self, f: &mut impl fmt::Write) -> fmt::Result {
        write!(f, "\x1b[{};{}r", self.0.start, self.0.end)
    }

    #[cfg(windows)]
    fn execute_winapi(&self) -> std::io::Result<()> {
        panic!("tried to execute SetScrollRegion command using WinAPI, use ANSI instead");
    }

    #[cfg(windows)]
    fn is_ansi_code_supported(&self) -> bool {
        // TODO(nornagon): is this supported on Windows?
        true
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct ResetScrollRegion;

impl Command for ResetScrollRegion {
    fn write_ansi(&self, f: &mut impl fmt::Write) -> fmt::Result {
        write!(f, "\x1b[r")
    }

    #[cfg(windows)]
    fn execute_winapi(&self) -> std::io::Result<()> {
        panic!("tried to execute ResetScrollRegion command using WinAPI, use ANSI instead");
    }

    #[cfg(windows)]
    fn is_ansi_code_supported(&self) -> bool {
        // TODO(nornagon): is this supported on Windows?
        true
    }
}

struct ModifierDiff {
    pub from: Modifier,
    pub to: Modifier,
}

impl ModifierDiff {
    fn queue<W>(self, mut w: W) -> io::Result<()>
    where
        W: io::Write,
    {
        use crossterm::style::Attribute as CAttribute;
        let removed = self.from - self.to;
        if removed.contains(Modifier::REVERSED) {
            queue!(w, SetAttribute(CAttribute::NoReverse))?;
        }
        if removed.contains(Modifier::BOLD) {
            queue!(w, SetAttribute(CAttribute::NormalIntensity))?;
            if self.to.contains(Modifier::DIM) {
                queue!(w, SetAttribute(CAttribute::Dim))?;
            }
        }
        if removed.contains(Modifier::ITALIC) {
            queue!(w, SetAttribute(CAttribute::NoItalic))?;
        }
        if removed.contains(Modifier::UNDERLINED) {
            queue!(w, SetAttribute(CAttribute::NoUnderline))?;
        }
        if removed.contains(Modifier::DIM) {
            queue!(w, SetAttribute(CAttribute::NormalIntensity))?;
        }
        if removed.contains(Modifier::CROSSED_OUT) {
            queue!(w, SetAttribute(CAttribute::NotCrossedOut))?;
        }
        if removed.contains(Modifier::SLOW_BLINK) || removed.contains(Modifier::RAPID_BLINK) {
            queue!(w, SetAttribute(CAttribute::NoBlink))?;
        }

        let added = self.to - self.from;
        if added.contains(Modifier::REVERSED) {
            queue!(w, SetAttribute(CAttribute::Reverse))?;
        }
        if added.contains(Modifier::BOLD) {
            queue!(w, SetAttribute(CAttribute::Bold))?;
        }
        if added.contains(Modifier::ITALIC) {
            queue!(w, SetAttribute(CAttribute::Italic))?;
        }
        if added.contains(Modifier::UNDERLINED) {
            queue!(w, SetAttribute(CAttribute::Underlined))?;
        }
        if added.contains(Modifier::DIM) {
            queue!(w, SetAttribute(CAttribute::Dim))?;
        }
        if added.contains(Modifier::CROSSED_OUT) {
            queue!(w, SetAttribute(CAttribute::CrossedOut))?;
        }
        if added.contains(Modifier::SLOW_BLINK) {
            queue!(w, SetAttribute(CAttribute::SlowBlink))?;
        }
        if added.contains(Modifier::RAPID_BLINK) {
            queue!(w, SetAttribute(CAttribute::RapidBlink))?;
        }

        Ok(())
    }
}

fn write_spans<'a, I>(mut writer: &mut impl Write, content: I) -> io::Result<()>
where
    I: Iterator<Item = &'a Span<'a>>,
{
    let mut fg = Color::Reset;
    let mut bg = Color::Reset;
    let mut last_modifier = Modifier::empty();
    for span in content {
        let mut modifier = Modifier::empty();
        modifier.insert(span.style.add_modifier);
        modifier.remove(span.style.sub_modifier);
        if modifier != last_modifier {
            let diff = ModifierDiff {
                from: last_modifier,
                to: modifier,
            };
            diff.queue(&mut writer)?;
            last_modifier = modifier;
        }
        let next_fg = span.style.fg.unwrap_or(Color::Reset);
        let next_bg = span.style.bg.unwrap_or(Color::Reset);
        if next_fg != fg || next_bg != bg {
            queue!(
                writer,
                SetColors(Colors::new(next_fg.into(), next_bg.into()))
            )?;
            fg = next_fg;
            bg = next_bg;
        }

        queue!(writer, Print(span.content.clone()))?;
    }

    queue!(
        writer,
        SetForegroundColor(CColor::Reset),
        SetBackgroundColor(CColor::Reset),
        SetAttribute(crossterm::style::Attribute::Reset),
    )
}

#[cfg(test)]
mod tests {
    #![allow(clippy::unwrap_used)]
    use super::*;

    #[test]
    fn writes_bold_then_regular_spans() {
        use ratatui::style::Stylize;

        let spans = ["A".bold(), "B".into()];

        let mut actual: Vec<u8> = Vec::new();
        write_spans(&mut actual, spans.iter()).unwrap();

        let mut expected: Vec<u8> = Vec::new();
        queue!(
            expected,
            SetAttribute(crossterm::style::Attribute::Bold),
            Print("A"),
            SetAttribute(crossterm::style::Attribute::NormalIntensity),
            Print("B"),
            SetForegroundColor(CColor::Reset),
            SetBackgroundColor(CColor::Reset),
            SetAttribute(crossterm::style::Attribute::Reset),
        )
        .unwrap();

        assert_eq!(
            String::from_utf8(actual).unwrap(),
            String::from_utf8(expected).unwrap()
        );
    }
}