use std::{
    cmp::{max, min},
    ffi::{CStr, CString, OsStr, c_void},
    fs,
    os::unix::ffi::OsStrExt,
    path::Path,
    ptr::{self, NonNull},
    slice,
};

use ::typst::{
    Document,
    layout::{Abs, FrameItem, Page, Point, Rect},
    model::Destination,
    text::{Glyph, TextItem},
};
use cairo::{Format, ImageSurface};

use crate::{
    typst::FrameItemIterator,
    zathura::{
        cairo_t, girara_list_t, zathura_document_get_data, zathura_document_get_path, zathura_document_s, zathura_document_set_data, zathura_document_set_number_of_pages, zathura_link_destination_type_e_ZATHURA_LINK_DESTINATION_UNKNOWN, zathura_link_destination_type_e_ZATHURA_LINK_DESTINATION_XYZ, zathura_link_free, zathura_link_new, zathura_link_target_s, zathura_link_type_e_ZATHURA_LINK_GOTO_DEST, zathura_link_type_e_ZATHURA_LINK_GOTO_REMOTE, zathura_link_type_e_ZATHURA_LINK_URI, zathura_page_get_document, zathura_page_get_index, zathura_page_set_data, zathura_page_set_height, zathura_page_set_width, zathura_page_t, zathura_rectangle_s, GiraraList, ZathuraResult
    },
};

mod typst;
mod zathura;
use typst::TypstDocument;

#[allow(non_upper_case_globals)]
#[unsafe(no_mangle)]
pub static zathura_plugin_6_7: zathura::zathura_plugin_definition_s =
    zathura::zathura_plugin_definition_s {
        name: c"zathura-typst".as_ptr(),
        version: zathura::zathura_plugin_version_s {
            major: 0,
            minor: 1,
            rev: 0,
        },
        functions: zathura::zathura_plugin_functions_s {
            document_open: Some(document_open),
            document_free: Some(document_free),
            document_index_generate: None, // TODO?
            document_save_as: Some(document_save_as),
            document_attachments_get: None,
            document_attachment_save: None,
            document_get_information: None, // TODO
            page_init: Some(page_init),
            page_clear: Some(page_clear),
            page_search_text: None, // TODO?
            page_links_get: Some(page_links_get),
            page_form_fields_get: None,
            page_images_get: None, // TODO?
            page_image_get_cairo: None,
            page_get_text: Some(page_get_text),
            page_get_selection: Some(page_get_selection),
            page_render_cairo: Some(page_render_cairo),
            page_get_label: None,
            page_get_signatures: None,
        },
        mime_types_size: 1,
        mime_types: {
            static MIMETYPES: &[&u8] = &[c"text/vnd.typst".to_bytes_with_nul().first().unwrap()];
            MIMETYPES.as_ptr() as *mut _
        },
    };

unsafe extern "C" fn document_open(doc: *mut zathura_document_s) -> ZathuraResult {
    let path = unsafe {
        Path::new(OsStr::from_bytes(
            CStr::from_ptr(zathura_document_get_path(doc)).to_bytes(),
        ))
    };
    let document = Box::new(TypstDocument::load(path));

    unsafe {
        zathura_document_set_number_of_pages(doc, document.doc.pages.len() as u32);
        zathura_document_set_data(doc, Box::into_raw(document) as _);
    }

    ZathuraResult::OK
}

unsafe extern "C" fn document_free(_: *mut zathura_document_s, data: *mut c_void) -> ZathuraResult {
    if !data.is_null() {
        drop(unsafe { Box::<TypstDocument>::from_raw(data as _) });
    }
    ZathuraResult::OK
}

unsafe extern "C" fn document_save_as(
    _: *mut zathura_document_s,
    data: *mut c_void,
    dst: *const i8,
) -> ZathuraResult {
    let typst_doc: &TypstDocument = unsafe { &*(data as *mut _) };
    let dst = Path::new(OsStr::from_bytes(unsafe { CStr::from_ptr(dst) }.to_bytes()));

    let Ok(bytes) = typst_pdf::pdf(&typst_doc.doc, &Default::default()) else {
        return ZathuraResult::Unknown;
    };
    let Ok(()) = fs::write(dst, bytes) else {
        return ZathuraResult::InvalidArguments;
    };

    ZathuraResult::OK
}

unsafe extern "C" fn page_init(page: *mut zathura_page_t) -> ZathuraResult {
    let pageno = unsafe { zathura_page_get_index(page) };
    let doc = unsafe { zathura_page_get_document(page) };
    let typst_doc = unsafe { &mut *(zathura_document_get_data(doc) as *mut TypstDocument) };

    let typst_page: &Page = &typst_doc.doc.pages[pageno as usize];

    unsafe {
        zathura_page_set_data(page, typst_page as *const _ as _);
        zathura_page_set_width(page, typst_page.frame.width().to_pt());
        zathura_page_set_height(page, typst_page.frame.height().to_pt());
    };

    ZathuraResult::OK
}

unsafe extern "C" fn page_clear(_: *mut zathura_page_t, _: *mut c_void) -> ZathuraResult {
    ZathuraResult::OK
}

unsafe extern "C" fn page_render_cairo(
    _page: *mut zathura_page_t,
    typst_page: *mut c_void,
    cairo: *mut cairo_t,
    _printing: bool,
) -> ZathuraResult {
    let typst_page: &Page = unsafe { &*(typst_page as *mut _) };

    let context = unsafe { cairo::Context::from_raw_none(cairo) };
    let surface = context.target();
    if surface.status().is_err() {
        return ZathuraResult::Unknown;
    }
    let Ok(surface) = ImageSurface::try_from(surface) else {
        return ZathuraResult::InvalidArguments;
    };

    let scale = {
        let wscale = surface.width() as f32 / typst_page.frame.width().to_pt() as f32;
        let vscale = surface.height() as f32 / typst_page.frame.height().to_pt() as f32;
        if vscale > wscale { vscale } else { wscale }
    };

    let format = surface.format();

    let pixels_rgba = typst_render::render(typst_page, scale);
    let render_width = pixels_rgba.width();
    let pixels_rgba = pixels_rgba.take();

    let (pixels_rgba, _) = pixels_rgba.as_chunks::<4>(); // This will always be exact anyway

    let buf = unsafe {
        std::slice::from_raw_parts_mut(
            cairo::ffi::cairo_image_surface_get_data(surface.to_raw_none()),
            surface.stride() as usize * surface.height() as usize,
        )
    };

    if !matches!(format, Format::ARgb32 | Format::Rgb24) {
        return ZathuraResult::Unknown;
    }

    pixels_rgba
        .chunks_exact(render_width as _)
        .zip(buf.chunks_mut(surface.stride() as _))
        .for_each(|(row, dst)| {
            row.iter()
                .zip(dst.chunks_exact_mut(4))
                .for_each(|(&[r, g, b, a], dst)| {
                    dst.copy_from_slice(&u32::from_be_bytes([a, r, g, b]).to_ne_bytes());
                })
        });

    surface.mark_dirty();

    ZathuraResult::OK
}

fn rect_intersection(a: Rect, b: Rect) -> Option<Rect> {
    Some(Rect::new(
        Point::new(max(a.min.x, b.min.x), max(a.min.y, b.min.y)),
        Point::new(min(a.max.x, b.max.x), min(a.max.y, b.max.y)),
    ))
    .filter(|r| r.size().all(|c| c.to_raw() >= 0.))
}

fn rect_union(a: Rect, b: Rect) -> Rect {
    Rect::new(
        Point::new(min(a.min.x, b.min.x), min(a.min.y, b.min.y)),
        Point::new(max(a.max.x, b.max.x), max(a.max.y, b.max.y)),
    )
}

fn rect_norm(a: Rect) -> Rect {
    Rect::new(
        Point::new(min(a.min.x, a.max.x), min(a.min.y, a.max.y)),
        Point::new(max(a.min.x, a.max.x), max(a.min.y, a.max.y)),
    )
}

fn selected_glyphs(
    selection: Rect,
    point: Point,
    item: &TextItem,
) -> Option<impl Iterator<Item = (Point, Rect, &Glyph)>> {
    let bbox = rect_norm(item.bbox());
    if bbox.size().any(|d| d.to_raw().is_infinite()) {
        return None;
    }
    let inter = rect_intersection(
        Rect::new(point + bbox.min, point + bbox.max),
        rect_norm(selection),
    )?;
    Some(
        item.glyphs
            .iter()
            .scan(point, move |cursor, glyph| {
                Some((*cursor, {
                    *cursor +=
                        Point::new(glyph.x_advance.at(item.size), glyph.y_advance.at(item.size));
                    glyph
                }))
            })
            .filter_map(move |(point, glyph)| {
                let bbox = item
                    .font
                    .ttf()
                    .glyph_bounding_box(ttf_parser::GlyphId(glyph.id))?;
                let base =
                    point + Point::new(glyph.x_offset.at(item.size), glyph.y_offset.at(item.size));
                let bbox = rect_norm(Rect::new(
                    base + Point::new(
                        item.font.to_em(bbox.x_min).at(item.size),
                        item.font.to_em(bbox.y_min).at(item.size),
                    ),
                    base + Point::new(
                        item.font.to_em(bbox.x_max).at(item.size),
                        item.font.to_em(bbox.y_max).at(item.size),
                    ),
                ));
                rect_intersection(inter, bbox).map(|_| (point, bbox, glyph))
            }),
    )
}

unsafe extern "C" fn page_get_text(
    _page: *mut zathura_page_t,
    data: *mut c_void,
    rect: zathura_rectangle_s,
    res: *mut ZathuraResult,
) -> *mut i8 {
    let res = if let Some(mut r) = NonNull::new(res) {
        unsafe {
            r.write(ZathuraResult::Unknown);
            r.as_mut()
        }
    } else {
        &mut ZathuraResult::OK
    };
    let typst_page: &Page = unsafe { &*(data as *mut _) };

    let rect = Rect::from(rect);
    let text = FrameItemIterator::new(&typst_page.frame)
        .filter_map(|(point, item)| {
            if let FrameItem::Text(item) = item {
                let mut ranges =
                    selected_glyphs(rect, point, item)?.map(|(_, _, glyph)| glyph.range());
                Some(item.text[ranges.next()?.start..ranges.last()?.end].to_owned())
            } else {
                None
            }
        })
        .collect::<String>();

    *res = ZathuraResult::OK;

    unsafe {
        let str = slice::from_raw_parts_mut(
            cairo::glib::ffi::g_malloc0_n(text.len() + 1, 1) as *mut u8,
            text.len() + 1,
        );
        str[..text.len()].copy_from_slice(text.as_bytes());

        str.as_mut_ptr() as _
    }
}

unsafe extern "C" fn page_get_selection(
    _page: *mut zathura_page_t,
    data: *mut c_void,
    rect: zathura_rectangle_s,
    res: *mut ZathuraResult,
) -> *mut girara_list_t {
    let res = if let Some(mut r) = NonNull::new(res) {
        unsafe {
            r.write(ZathuraResult::Unknown);
            r.as_mut()
        }
    } else {
        &mut ZathuraResult::OK
    };
    let typst_page: &Page = unsafe { &*(data as *mut _) };

    let rect = Rect::from(rect);

    let rects = FrameItemIterator::new(&typst_page.frame).filter_map(|(point, item)| {
        if let FrameItem::Text(item) = item {
            let bbox = selected_glyphs(rect, point, item)?.fold(
                Rect::new(Point::splat(Abs::inf()), Point::splat(-Abs::inf())),
                |acc, (_, bbox, _)| rect_union(acc, bbox),
            );
            Some(bbox)
        } else {
            None
        }
    });

    *res = ZathuraResult::OK;
    rects
        .map(zathura_rectangle_s::from)
        .collect::<GiraraList<zathura_rectangle_s>>()
        .into_raw()
}

unsafe extern "C" fn page_links_get(
    zpage: *mut zathura_page_t,
    page: *mut c_void,
    res: *mut ZathuraResult,
) -> *mut girara_list_t {
    let res = if let Some(mut r) = NonNull::new(res) {
        unsafe {
            r.write(ZathuraResult::Unknown);
            r.as_mut()
        }
    } else {
        &mut ZathuraResult::OK
    };
    let doc = unsafe {
        &mut (*(zathura_document_get_data(zathura_page_get_document(zpage)) as *mut TypstDocument))
    };

    let page: &Page = unsafe { &*(page as *const _) };

    let links = FrameItemIterator::new(&page.frame)
        .filter_map(|(point, item)| {
            if let FrameItem::Link(dst, size) = item {
                Some((Rect::from_pos_size(point, *size), dst))
            } else {
                None
            }
        })
        .map(|(rect, dst)| {
            let (ty, target) = match dst {
                Destination::Url(url) => (
                    if url.starts_with("file://") {
                        zathura_link_type_e_ZATHURA_LINK_GOTO_REMOTE
                    } else {
                        zathura_link_type_e_ZATHURA_LINK_URI
                    },
                    zathura_link_target_s {
                        destination_type:
                            zathura_link_destination_type_e_ZATHURA_LINK_DESTINATION_UNKNOWN,
                        value: doc
                            .cstring_cache
                            .entry(url.to_string())
                            .or_insert_with(|| {
                                CString::new(url.as_bytes()).expect("URL shouldn't contain NUL")
                            })
                            .as_ptr() as *mut i8,
                        page_number: 0,
                        left: -1.,
                        right: -1.,
                        top: -1.,
                        bottom: -1.,
                        zoom: 0.,
                    },
                ),
                Destination::Position(position) => (
                    zathura_link_type_e_ZATHURA_LINK_GOTO_DEST,
                    zathura_link_target_s {
                        destination_type:
                            zathura_link_destination_type_e_ZATHURA_LINK_DESTINATION_XYZ,
                        value: ptr::null_mut(),
                        page_number: position.page.get() as u32 - 1,
                        left: position.point.x.to_pt(),
                        right: -1.,
                        top: position.point.y.to_pt(),
                        bottom: -1.,
                        zoom: 0.,
                    },
                ),
                Destination::Location(location) => {
                    let position = doc.doc.introspector().position(*location);
                    (
                        zathura_link_type_e_ZATHURA_LINK_GOTO_DEST,
                        zathura_link_target_s {
                            destination_type:
                                zathura_link_destination_type_e_ZATHURA_LINK_DESTINATION_XYZ,
                            value: ptr::null_mut(),
                            page_number: position.page.get() as u32 - 1,
                            left: position.point.x.to_pt(),
                            right: -1.,
                            top: position.point.y.to_pt(),
                            bottom: -1.,
                            zoom: 0.,
                        },
                    )
                }
            };            
            unsafe { zathura_link_new(ty, rect.into(), target) }
        });

    unsafe {
        let mut links_ = GiraraList::new_with_free(zathura_link_free);
        links_.extend_allocated(links);
        *res = ZathuraResult::OK;
        links_.into_raw()
    }
}

// TODO: render warnings
// TODO: better caching