use std::cmp;
use std::collections::VecDeque;

use console_draw::{Damage, TextScreen, V2DisplayMap};
use drm::buffer::Buffer;
use drm::control::Device;
use graphics_ipc::V2GraphicsHandle;
use inputd::ConsumerHandle;
use orbclient::{Event, EventOption};
use redox_scheme::scheme::SchemeSync;
use redox_scheme::{CallerCtx, OpenResult};
use scheme_utils::FpathWriter;
use syscall::schemev2::NewFdFlags;
use syscall::{Error, Result, EACCES, EBADF, EINVAL, ENOENT};

pub struct FbbootlogScheme {
    pub input_handle: ConsumerHandle,
    display_map: Option<V2DisplayMap>,
    text_screen: console_draw::TextScreen,
    text_buffer: console_draw::TextBuffer,
    is_scrollback: bool,
    scrollback_offset: usize,
    shift: bool,
}

impl FbbootlogScheme {
    pub fn new() -> FbbootlogScheme {
        let mut scheme = FbbootlogScheme {
            input_handle: ConsumerHandle::bootlog_vt().expect("fbbootlogd: Failed to open vt"),
            display_map: None,
            text_screen: console_draw::TextScreen::new(),
            text_buffer: console_draw::TextBuffer::new(1000),
            is_scrollback: false,
            scrollback_offset: 1000,
            shift: false,
        };

        scheme.handle_handoff();

        scheme
    }

    pub fn handle_handoff(&mut self) {
        let new_display_handle = match self.input_handle.open_display_v2() {
            Ok(display) => V2GraphicsHandle::from_file(display).unwrap(),
            Err(err) => {
                eprintln!("fbbootlogd: No display present yet: {err}");
                return;
            }
        };

        match V2DisplayMap::new(new_display_handle) {
            Ok(display_map) => self.display_map = Some(display_map),
            Err(err) => {
                eprintln!("fbbootlogd: failed to open display: {}", err);
                return;
            }
        };

        eprintln!("fbbootlogd: mapped display");
    }

    pub fn handle_input(&mut self, ev: &Event) {
        match ev.to_option() {
            EventOption::Key(key_event) => {
                if key_event.scancode == 0x2A || key_event.scancode == 0x36 {
                    self.shift = key_event.pressed;
                } else if !key_event.pressed || !self.shift {
                    return;
                }
                match key_event.scancode {
                    0x48 => {
                        // Up
                        if self.scrollback_offset >= 1 {
                            self.scrollback_offset -= 1;
                        }
                    }
                    0x49 => {
                        // Page up
                        if self.scrollback_offset >= 10 {
                            self.scrollback_offset -= 10;
                        } else {
                            self.scrollback_offset = 0;
                        }
                    }
                    0x50 => {
                        // Down
                        self.scrollback_offset += 1;
                    }
                    0x51 => {
                        // Page down
                        self.scrollback_offset += 10;
                    }
                    0x47 => {
                        // Home
                        self.scrollback_offset = 0;
                    }
                    0x4F => {
                        // End
                        self.scrollback_offset = self.text_buffer.lines_max;
                    }
                    _ => return,
                }
            }
            _ => return,
        }
        self.handle_scrollback_render();
    }

    fn handle_scrollback_render(&mut self) {
        let Some(map) = &mut self.display_map else {
            return;
        };
        let buffer_len = self.text_buffer.lines.len();
        // for both extra space on wrapping text and a scrollback indicator
        let spare_lines = 3;
        self.is_scrollback = true;
        self.scrollback_offset = cmp::min(
            self.scrollback_offset,
            buffer_len - map.buffer.buffer().size().1 as usize / 16 + spare_lines,
        );
        let mut i = self.scrollback_offset;
        self.text_screen
            .write(map, b"\x1B[1;1H\x1B[2J", &mut VecDeque::new());

        let mut total_damage = Damage::NONE;
        while i < buffer_len {
            let mut damage =
                self.text_screen
                    .write(map, &self.text_buffer.lines[i][..], &mut VecDeque::new());
            i += 1;
            let yd = (damage.y + damage.height) as usize;
            if i == buffer_len || yd + spare_lines * 16 > map.buffer.buffer().size().1 as usize {
                // render until end of screen
                damage.height = map.buffer.buffer().size().1 - damage.y;
                total_damage = total_damage.merge(damage);
                self.is_scrollback = i < buffer_len;
                break;
            } else {
                total_damage = total_damage.merge(damage);
            }
        }
        map.dirty_fb(total_damage).unwrap();
    }

    fn handle_resize(map: &mut V2DisplayMap, text_screen: &mut TextScreen) {
        let mode = match map
            .display_handle
            .first_display()
            .and_then(|handle| Ok(map.display_handle.get_connector(handle, true)?.modes()[0]))
        {
            Ok(mode) => mode,
            Err(err) => {
                eprintln!("fbbootlogd: failed to get display size: {}", err);
                return;
            }
        };

        if (u32::from(mode.size().0), u32::from(mode.size().1)) != map.buffer.buffer().size() {
            match text_screen.resize(map, mode) {
                Ok(()) => eprintln!("fbbootlogd: mapped display"),
                Err(err) => {
                    eprintln!("fbbootlogd: failed to create or map framebuffer: {}", err);
                    return;
                }
            }
        }
    }
}

const SCHEME_ROOT_ID: usize = 1;

impl SchemeSync for FbbootlogScheme {
    fn scheme_root(&mut self) -> Result<usize> {
        Ok(SCHEME_ROOT_ID)
    }

    fn openat(
        &mut self,
        dirfd: usize,
        path_str: &str,
        _flags: usize,
        _fcntl_flags: u32,
        _ctx: &CallerCtx,
    ) -> Result<OpenResult> {
        if dirfd != SCHEME_ROOT_ID {
            return Err(Error::new(EACCES));
        }
        if !path_str.is_empty() {
            return Err(Error::new(ENOENT));
        }

        Ok(OpenResult::ThisScheme {
            number: 0,
            flags: NewFdFlags::empty(),
        })
    }

    fn fpath(&mut self, _id: usize, buf: &mut [u8], _ctx: &CallerCtx) -> Result<usize> {
        FpathWriter::with_legacy(buf, "fbbootlog", |_| Ok(()))
    }

    fn fsync(&mut self, _id: usize, _ctx: &CallerCtx) -> Result<()> {
        Ok(())
    }

    fn read(
        &mut self,
        _id: usize,
        _buf: &mut [u8],
        _offset: u64,
        _fcntl_flags: u32,
        _ctx: &CallerCtx,
    ) -> Result<usize> {
        Err(Error::new(EINVAL))
    }

    fn write(
        &mut self,
        id: usize,
        buf: &[u8],
        _offset: u64,
        _fcntl_flags: u32,
        _ctx: &CallerCtx,
    ) -> Result<usize> {
        if id == SCHEME_ROOT_ID {
            return Err(Error::new(EBADF));
        }
        if let Some(map) = &mut self.display_map {
            Self::handle_resize(map, &mut self.text_screen);
            self.text_buffer.write(buf);

            if !self.is_scrollback {
                let damage = self.text_screen.write(map, buf, &mut VecDeque::new());

                if let Some(map) = &mut self.display_map {
                    map.dirty_fb(damage).unwrap();
                }
            }
        }

        Ok(buf.len())
    }
}