// Copyright: Ankitects Pty Ltd and contributors
// License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html

use std::borrow::Cow;
use std::collections::HashMap;
use std::ffi::OsString;
use std::fs;
use std::fs::File;
use std::io;
use std::io::Read;
use std::io::Write;
use std::path::Path;
use std::path::PathBuf;

use prost::Message;
use sha1::Digest;
use sha1::Sha1;
use zip::read::ZipFile;
use zip::ZipArchive;
use zstd::stream::copy_decode;
use zstd::stream::raw::Encoder as RawEncoder;

use super::meta::MetaExt;
use super::MediaEntries;
use super::MediaEntry;
use super::Meta;
use crate::error::FileIoError;
use crate::error::FileOp;
use crate::error::InvalidInputError;
use crate::import_export::package::colpkg::export::MaybeEncodedWriter;
use crate::import_export::ImportError;
use crate::io::atomic_rename;
use crate::io::filename_is_safe;
use crate::io::new_tempfile_in;
use crate::io::read_dir_files;
use crate::media::files::filename_if_normalized;
use crate::media::files::normalize_filename;
use crate::prelude::*;

/// Like [MediaEntry], but with a safe filename and set zip filename.
pub(super) struct SafeMediaEntry {
    pub(super) name: String,
    pub(super) size: u32,
    pub(super) sha1: Option<Sha1Hash>,
    pub(super) index: usize,
}

pub(super) fn new_media_entry(
    name: impl Into<String>,
    size: impl TryInto<u32>,
    sha1: impl Into<Vec<u8>>,
) -> MediaEntry {
    MediaEntry {
        name: name.into(),
        size: size.try_into().unwrap_or_default(),
        sha1: sha1.into(),
        legacy_zip_filename: None,
    }
}

impl SafeMediaEntry {
    pub(super) fn from_entry(enumerated: (usize, MediaEntry)) -> Result<Self> {
        let (index, entry) = enumerated;
        if let Ok(sha1) = entry.sha1.try_into() {
            if !matches!(safe_normalized_file_name(&entry.name)?, Cow::Owned(_)) {
                return Ok(Self {
                    name: entry.name,
                    size: entry.size,
                    sha1: Some(sha1),
                    index,
                });
            }
        }
        Err(AnkiError::ImportError {
            source: ImportError::Corrupt,
        })
    }

    pub(super) fn from_legacy(legacy_entry: (&str, String)) -> Result<Self> {
        let zip_filename: usize = legacy_entry.0.parse()?;
        let name = match safe_normalized_file_name(&legacy_entry.1)? {
            Cow::Owned(new_name) => new_name,
            Cow::Borrowed(_) => legacy_entry.1,
        };
        Ok(Self {
            name,
            size: 0,
            sha1: None,
            index: zip_filename,
        })
    }

    pub(super) fn file_path(&self, media_folder: &Path) -> PathBuf {
        media_folder.join(&self.name)
    }

    pub(super) fn fetch_file<'a>(&self, archive: &'a mut ZipArchive<File>) -> Result<ZipFile<'a>> {
        match archive.by_name(&self.index.to_string()) {
            Ok(file) => Ok(file),
            Err(err) => invalid_input!(err, "{} missing from archive", self.index),
        }
    }

    pub(super) fn has_checksum_equal_to(
        &self,
        get_checksum: &mut impl FnMut(&str) -> Result<Option<Sha1Hash>>,
    ) -> Result<bool> {
        get_checksum(&self.name)
            .map(|opt| opt.map_or(false, |sha1| sha1 == self.sha1.expect("sha1 not set")))
    }

    pub(super) fn has_size_equal_to(&self, other_path: &Path) -> bool {
        fs::metadata(other_path).map_or(false, |metadata| metadata.len() == self.size as u64)
    }

    /// Copy the archived file to the target folder, setting its hash if
    /// necessary.
    pub(super) fn copy_and_ensure_sha1_set(
        &mut self,
        archive: &mut ZipArchive<File>,
        target_folder: &Path,
        copier: &mut MediaCopier,
        compressed: bool,
    ) -> Result<()> {
        let mut file = self.fetch_file(archive)?;
        let mut tempfile = new_tempfile_in(target_folder)?;
        if compressed {
            copy_decode(&mut file, &mut tempfile)?
        } else {
            let (_, sha1) = copier.copy(&mut file, &mut tempfile)?;
            self.sha1 = Some(sha1);
        }
        atomic_rename(tempfile, &self.file_path(target_folder), false)?;

        Ok(())
    }
}

pub(super) fn extract_media_entries(
    meta: &Meta,
    archive: &mut ZipArchive<File>,
) -> Result<Vec<SafeMediaEntry>> {
    let media_list_data = get_media_list_data(archive, meta)?;
    if meta.media_list_is_hashmap() {
        let map: HashMap<&str, String> = serde_json::from_slice(&media_list_data)?;
        map.into_iter().map(SafeMediaEntry::from_legacy).collect()
    } else {
        decode_safe_entries(&media_list_data)
    }
}

pub(super) fn safe_normalized_file_name(name: &str) -> Result<Cow<str>> {
    if !filename_is_safe(name) {
        Err(AnkiError::ImportError {
            source: ImportError::Corrupt,
        })
    } else {
        Ok(normalize_filename(name))
    }
}

fn get_media_list_data(archive: &mut ZipArchive<File>, meta: &Meta) -> Result<Vec<u8>> {
    let mut file = archive.by_name("media")?;
    let mut buf = Vec::new();
    if meta.zstd_compressed() {
        copy_decode(file, &mut buf)?;
    } else {
        io::copy(&mut file, &mut buf)?;
    }
    Ok(buf)
}

pub(super) fn decode_safe_entries(buf: &[u8]) -> Result<Vec<SafeMediaEntry>> {
    let entries: MediaEntries = Message::decode(buf)?;
    entries
        .entries
        .into_iter()
        .enumerate()
        .map(SafeMediaEntry::from_entry)
        .collect()
}

pub struct MediaIterEntry {
    pub nfc_filename: String,
    pub data: Box<dyn Read>,
}

#[derive(Debug)]
pub enum MediaIterError {
    InvalidFilename {
        filename: OsString,
    },
    IoError {
        filename: String,
        source: io::Error,
    },
    Other {
        source: Box<dyn std::error::Error + Send + Sync>,
    },
}

impl TryFrom<&Path> for MediaIterEntry {
    type Error = MediaIterError;

    fn try_from(value: &Path) -> std::result::Result<Self, Self::Error> {
        let nfc_filename: String = value
            .file_name()
            .and_then(|s| s.to_str())
            .and_then(filename_if_normalized)
            .ok_or_else(|| MediaIterError::InvalidFilename {
                filename: value.as_os_str().to_owned(),
            })?
            .into();
        let file = File::open(value).map_err(|err| MediaIterError::IoError {
            filename: nfc_filename.clone(),
            source: err,
        })?;
        Ok(MediaIterEntry {
            nfc_filename,
            data: Box::new(file) as _,
        })
    }
}

impl From<MediaIterError> for AnkiError {
    fn from(err: MediaIterError) -> Self {
        match err {
            MediaIterError::InvalidFilename { .. } => AnkiError::MediaCheckRequired,
            MediaIterError::IoError { filename, source } => FileIoError {
                path: filename.into(),
                op: FileOp::Read,
                source,
            }
            .into(),
            MediaIterError::Other { source } => InvalidInputError {
                message: "".to_string(),
                source: Some(source),
                backtrace: None,
            }
            .into(),
        }
    }
}

pub struct MediaIter(pub Box<dyn Iterator<Item = Result<MediaIterEntry, MediaIterError>>>);

impl MediaIter {
    pub fn new<I>(iter: I) -> Self
    where
        I: Iterator<Item = Result<MediaIterEntry, MediaIterError>> + 'static,
    {
        Self(Box::new(iter))
    }

    /// Iterator over all files in the given path, without traversing
    /// subfolders.
    pub fn from_folder(path: &Path) -> Result<Self> {
        let path2 = path.to_owned();
        Ok(Self::new(read_dir_files(path)?.map(move |res| match res {
            Ok(entry) => MediaIterEntry::try_from(entry.path().as_path()),
            Err(err) => Err(MediaIterError::IoError {
                filename: path2.to_string_lossy().into(),
                source: err,
            }),
        })))
    }

    /// Iterator over all given files in the given folder.
    /// Missing files are silently ignored.
    pub fn from_file_list(
        list: impl IntoIterator<Item = String> + 'static,
        folder: PathBuf,
    ) -> Self {
        Self::new(
            list.into_iter()
                .map(move |file| folder.join(file))
                .filter(|path| path.exists())
                .map(|path| MediaIterEntry::try_from(path.as_path())),
        )
    }

    pub fn empty() -> Self {
        Self::new([].into_iter())
    }
}

/// Copies and hashes while optionally encoding.
/// If compressing, the encoder is reused to optimize for repeated calls.
pub(crate) struct MediaCopier {
    encoding: bool,
    encoder: Option<RawEncoder<'static>>,
    buf: [u8; 64 * 1024],
}

impl MediaCopier {
    pub(crate) fn new(encoding: bool) -> Self {
        Self {
            encoding,
            encoder: None,
            buf: [0; 64 * 1024],
        }
    }

    fn encoder(&mut self) -> Option<RawEncoder<'static>> {
        self.encoding.then(|| {
            self.encoder
                .take()
                .unwrap_or_else(|| RawEncoder::with_dictionary(0, &[]).unwrap())
        })
    }

    /// Returns size and sha1 hash of the copied data.
    pub(crate) fn copy(
        &mut self,
        reader: &mut impl Read,
        writer: &mut impl Write,
    ) -> Result<(usize, Sha1Hash)> {
        let mut size = 0;
        let mut hasher = Sha1::new();
        self.buf = [0; 64 * 1024];
        let mut wrapped_writer = MaybeEncodedWriter::new(writer, self.encoder());

        loop {
            let count = match reader.read(&mut self.buf) {
                Ok(0) => break,
                Err(e) if e.kind() == io::ErrorKind::Interrupted => continue,
                result => result?,
            };
            size += count;
            hasher.update(&self.buf[..count]);
            wrapped_writer.write(&self.buf[..count])?;
        }

        self.encoder = wrapped_writer.finish()?;

        Ok((size, hasher.finalize().into()))
    }
}

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn normalization() {
        // legacy entries get normalized on deserialisation
        let entry = SafeMediaEntry::from_legacy(("1", "con".to_owned())).unwrap();
        assert_eq!(entry.name, "con_");

        // new-style entries should have been normalized on export
        let mut entries = Vec::new();
        MediaEntries {
            entries: vec![new_media_entry("con", 0, Vec::new())],
        }
        .encode(&mut entries)
        .unwrap();
        assert!(decode_safe_entries(&entries).is_err());
    }
}