use crate::{config::FileserverConfig, ServiceError};
use bytes::{Bytes, BytesMut};
use futures_util::{future, future::Either, ready, stream, FutureExt, Stream, StreamExt};
use headers::{AcceptRanges, ContentLength, ContentRange, ContentType, HeaderMapExt};
use http_body_util::{combinators::BoxBody, BodyExt, StreamBody};
use humansize::FormatSizeOptions;
use hyper::{
    body::{Frame, Incoming},
    header::{CONTENT_TYPE, LOCATION},
    http::HeaderValue,
    Request, Response, StatusCode,
};
use log::debug;
use markup::Render;
use percent_encoding::percent_decode_str;
use std::{fs::Metadata, io, ops::Range, path::Path, pin::Pin, task::Poll};
use tokio::{
    fs::{read_to_string, File},
    io::AsyncSeekExt,
};
use tokio_util::io::poll_read_buf;

pub async fn serve_files(
    req: &Request<Incoming>,
    config: &FileserverConfig,
) -> Result<hyper::Response<BoxBody<Bytes, ServiceError>>, ServiceError> {
    let rpath = req.uri().path();

    let mut path = config.root.clone();
    let mut user_path_depth = 0;
    for seg in rpath.split("/") {
        let seg = percent_decode_str(seg).decode_utf8()?;

        if seg == "" || seg == "." {
            continue;
        }

        if seg == ".." {
            if user_path_depth <= 0 {
                return Err(ServiceError::BadPath);
            }
            path.pop();
            user_path_depth -= 1;
        } else {
            path.push(seg.as_ref());
            user_path_depth += 1;
        }
    }
    if !path.exists() {
        return Err(ServiceError::NotFound);
    }

    let metadata = path.metadata()?;

    if metadata.file_type().is_dir() {
        if !config.index {
            return Err(ServiceError::NotFound);
        }
        debug!("sending index for {path:?}");

        if !rpath.ends_with("/") {
            let mut r = Response::new(String::new());
            *r.status_mut() = StatusCode::FOUND;
            r.headers_mut().insert(
                LOCATION,
                HeaderValue::from_str(&format!("{}/", rpath)).map_err(|_| ServiceError::Other)?,
            );
            return Ok(r.map(|b| b.map_err(|e| match e {}).boxed()));
        }

        return index(&path, rpath.to_string()).await.map(|s| {
            let mut r = Response::new(s);
            r.headers_mut()
                .insert(CONTENT_TYPE, HeaderValue::from_static("text/html"));
            r.map(|b| b.map_err(|e| match e {}).boxed())
        });
    }

    let range = req.headers().typed_get::<headers::Range>();
    let range = bytes_range(range, metadata.len())?;

    debug!("sending file {path:?}");
    let file = File::open(path.clone()).await?;

    let mut r = Response::new(BoxBody::new(StreamBody::new(
        StreamBody::new(file_stream(file, 4096, range.clone()))
            .map(|e| e.map(|e| Frame::data(e)).map_err(ServiceError::Io)),
    )));

    if range.end - range.start != metadata.len() {
        *r.status_mut() = StatusCode::PARTIAL_CONTENT;
        r.headers_mut().typed_insert(
            ContentRange::bytes(range.clone(), metadata.len()).expect("valid ContentRange"),
        );
    }

    let mime = mime_guess::from_path(path).first_or_octet_stream();

    r.headers_mut()
        .typed_insert(ContentLength(range.end - range.start));
    r.headers_mut().typed_insert(ContentType::from(mime));
    r.headers_mut().typed_insert(AcceptRanges::bytes());

    Ok(r)
}

// Adapted from warp (https://github.com/seanmonstar/warp/blob/master/src/filters/fs.rs). Thanks!
fn file_stream(
    mut file: File,
    buf_size: usize,
    range: Range<u64>,
) -> impl Stream<Item = Result<Bytes, io::Error>> + Send {
    use std::io::SeekFrom;

    let seek = async move {
        if range.start != 0 {
            file.seek(SeekFrom::Start(range.start)).await?;
        }
        Ok(file)
    };

    seek.into_stream()
        .map(move |result| {
            let mut buf = BytesMut::new();
            let mut len = range.end - range.start;
            let mut f = match result {
                Ok(f) => f,
                Err(f) => return Either::Left(stream::once(future::err(f))),
            };

            Either::Right(stream::poll_fn(move |cx| {
                if len == 0 {
                    return Poll::Ready(None);
                }
                reserve_at_least(&mut buf, buf_size);

                let n = match ready!(poll_read_buf(Pin::new(&mut f), cx, &mut buf)) {
                    Ok(n) => n as u64,
                    Err(err) => {
                        debug!("file read error: {}", err);
                        return Poll::Ready(Some(Err(err)));
                    }
                };

                if n == 0 {
                    debug!("file read found EOF before expected length");
                    return Poll::Ready(None);
                }

                let mut chunk = buf.split().freeze();
                if n > len {
                    chunk = chunk.split_to(len as usize);
                    len = 0;
                } else {
                    len -= n;
                }

                Poll::Ready(Some(Ok(chunk)))
            }))
        })
        .flatten()
}

// Also adapted from warp
fn bytes_range(range: Option<headers::Range>, max_len: u64) -> Result<Range<u64>, ServiceError> {
    use std::ops::Bound;

    let range = if let Some(range) = range {
        range
    } else {
        return Ok(0..max_len);
    };

    let ret = range
        .iter()
        .map(|(start, end)| {
            let start = match start {
                Bound::Unbounded => 0,
                Bound::Included(s) => s,
                Bound::Excluded(s) => s + 1,
            };

            let end = match end {
                Bound::Unbounded => max_len,
                Bound::Included(s) => {
                    // For the special case where s == the file size
                    if s == max_len {
                        s
                    } else {
                        s + 1
                    }
                }
                Bound::Excluded(s) => s,
            };

            if start < end && end <= max_len {
                Ok(start..end)
            } else {
                Err(ServiceError::BadRange)
            }
        })
        .next()
        .unwrap_or(Ok(0..max_len));
    ret
}

fn reserve_at_least(buf: &mut BytesMut, cap: usize) {
    if buf.capacity() - buf.len() < cap {
        buf.reserve(cap);
    }
}

async fn index(path: &Path, rpath: String) -> Result<String, ServiceError> {
    let files = path
        .read_dir()?
        .map(|e| e.and_then(|e| Ok((e.file_name().into_string().unwrap(), e.metadata()?))))
        .filter(|e| e.as_ref().map(|(e, _)| !e.starts_with(".")).unwrap_or(true))
        .collect::<Result<Vec<_>, _>>()?;
    if let Ok(indexhtml) = read_to_string(path.join("index.html")).await {
        Ok(indexhtml)
    } else {
        let banner = read_to_string(path.join("index.banner.html")).await.ok();
        let mut s = String::new();
        IndexTemplate {
            files,
            banner,
            path: rpath,
        }
        .render(&mut s)
        .unwrap();
        Ok(s)
    }
}

markup::define! {
    IndexTemplate(path: String, banner: Option<String>, files: Vec<(String, Metadata)>) {
        @markup::doctype()
        html {
            head {
                meta[charset="UTF-8"];
                title { "Index of " @path }
            }
            body {
                @if let Some(banner) = banner {
                    @markup::raw(banner)
                } else {
                    h1 { "Index of " @path }
                }
                hr;
                table {
                    @if path != "/" {
                        tr { td { b { a[href=".."] { "../" } } } }
                    }
                    @for (name, meta) in files { tr {
                        td { a[href=name] {
                            @name
                            @if meta.file_type().is_dir() { "/" }
                        } }
                        td {
                            @if meta.file_type().is_dir() {
                                i { "directory" }
                            } else {
                                @humansize::format_size(meta.len(), FormatSizeOptions::default())
                            }
                        }
                    } }
                }
                hr;
                footer { sub { "served by " a[href="https://codeberg.org/metamuffin/gnix"] { "gnix" } } }
            }
        }
    }
}