//! Interfaces for interacting with different types of TUF repositories.

use hyper::{Url, Client};
use hyper::client::response::Response;
use hyper::header::{Headers, UserAgent};
use hyper::status::StatusCode;
use std::collections::HashMap;
use std::fs::{self, File, DirBuilder};
use std::io::{Read, Write, Cursor};
use std::marker::PhantomData;
use std::path::PathBuf;
use tempfile::NamedTempFile;

use Result;
use crypto::{self, HashAlgorithm, HashValue};
use error::Error;
use interchange::DataInterchange;
use metadata::{SignedMetadata, MetadataVersion, Role, Metadata, TargetPath, TargetDescription,
               MetadataPath};
use util::SafeReader;

/// Top-level trait that represents a TUF repository and contains all the ways it can be interacted
/// with.
pub trait Repository<D>
where
    D: DataInterchange,
{
    /// The type returned when reading a target.
    type TargetRead: Read;

    /// Initialize the repository.
    fn initialize(&mut self) -> Result<()>;

    /// Store signed metadata.
    ///
    /// Note: This **MUST** canonicalize the bytes before storing them as a read will expect the
    /// hashes of the metadata to match.
    fn store_metadata<M>(
        &mut self,
        role: &Role,
        meta_path: &MetadataPath,
        version: &MetadataVersion,
        metadata: &SignedMetadata<D, M>,
    ) -> Result<()>
    where
        M: Metadata;

    /// Fetch signed metadata.
    fn fetch_metadata<M>(
        &mut self,
        role: &Role,
        meta_path: &MetadataPath,
        version: &MetadataVersion,
        max_size: &Option<usize>,
        min_bytes_per_second: u32,
        hash_data: Option<(&HashAlgorithm, HashValue)>,
    ) -> Result<SignedMetadata<D, M>>
    where
        M: Metadata;

    /// Store the given target.
    fn store_target<R>(&mut self, read: R, target_path: &TargetPath) -> Result<()>
    where
        R: Read;

    /// Fetch the given target.
    fn fetch_target(
        &mut self,
        target_path: &TargetPath,
        target_description: &TargetDescription,
        min_bytes_per_second: u32,
    ) -> Result<SafeReader<Self::TargetRead>>;

    /// Perform a sanity check that `M`, `Role`, and `MetadataPath` all desrcribe the same entity.
    fn check<M>(role: &Role, meta_path: &MetadataPath) -> Result<()>
    where
        M: Metadata,
    {
        if role != &M::role() {
            return Err(Error::IllegalArgument(format!(
                "Attempted to store {} metadata as {}.",
                M::role(),
                role
            )));
        }

        if !role.fuzzy_matches_path(meta_path) {
            return Err(Error::IllegalArgument(
                format!("Role {} does not match path {:?}", role, meta_path),
            ));
        }

        Ok(())
    }
}

/// A repository contained on the local file system.
pub struct FileSystemRepository<D>
where
    D: DataInterchange,
{
    local_path: PathBuf,
    interchange: PhantomData<D>,
}

impl<D> FileSystemRepository<D>
where
    D: DataInterchange,
{
    /// Create a new repository on the local file system.
    pub fn new(local_path: PathBuf) -> Self {
        FileSystemRepository {
            local_path: local_path,
            interchange: PhantomData,
        }
    }
}

impl<D> Repository<D> for FileSystemRepository<D>
where
    D: DataInterchange,
{
    type TargetRead = File;

    fn initialize(&mut self) -> Result<()> {
        for p in &["metadata", "targets", "temp"] {
            DirBuilder::new().recursive(true).create(
                self.local_path.join(p),
            )?
        }

        Ok(())
    }

    fn store_metadata<M>(
        &mut self,
        role: &Role,
        meta_path: &MetadataPath,
        version: &MetadataVersion,
        metadata: &SignedMetadata<D, M>,
    ) -> Result<()>
    where
        M: Metadata,
    {
        Self::check::<M>(role, meta_path)?;

        let mut path = self.local_path.join("metadata");
        path.extend(meta_path.components::<D>(version));

        if path.exists() {
            debug!("Metadata path exists. Deleting: {:?}", path);
            fs::remove_file(&path)?
        }

        let mut file = File::create(&path)?;
        D::to_writer(&mut file, metadata)?;
        Ok(())

    }

    /// Fetch signed metadata.
    fn fetch_metadata<M>(
        &mut self,
        role: &Role,
        meta_path: &MetadataPath,
        version: &MetadataVersion,
        max_size: &Option<usize>,
        min_bytes_per_second: u32,
        hash_data: Option<(&HashAlgorithm, HashValue)>,
    ) -> Result<SignedMetadata<D, M>>
    where
        M: Metadata,
    {
        Self::check::<M>(role, meta_path)?;

        let mut path = self.local_path.join("metadata");
        path.extend(meta_path.components::<D>(&version));

        let read = SafeReader::new(
            File::open(&path)?,
            max_size.unwrap_or(::std::usize::MAX) as u64,
            min_bytes_per_second,
            hash_data,
        );

        Ok(D::from_reader(read)?)
    }

    fn store_target<R>(&mut self, mut read: R, target_path: &TargetPath) -> Result<()>
    where
        R: Read,
    {
        let mut temp_file = NamedTempFile::new_in(self.local_path.join("temp"))?;
        let mut buf = [0; 1024];
        loop {
            let bytes_read = read.read(&mut buf)?;
            if bytes_read == 0 {
                break;
            }
            temp_file.write_all(&buf[..bytes_read])?
        }

        let mut path = self.local_path.clone().join("targets");
        path.extend(target_path.components());
        temp_file.persist(&path)?;

        Ok(())
    }

    fn fetch_target(
        &mut self,
        target_path: &TargetPath,
        target_description: &TargetDescription,
        min_bytes_per_second: u32,
    ) -> Result<SafeReader<Self::TargetRead>> {
        let mut path = self.local_path.join("targets");
        path.extend(target_path.components());

        if !path.exists() {
            return Err(Error::NotFound);
        }

        let (alg, value) = crypto::hash_preference(target_description.hashes())?;

        Ok(SafeReader::new(
            File::open(&path)?,
            target_description.size(),
            min_bytes_per_second,
            Some((alg, value.clone())),
        ))
    }
}


/// A repository accessible over HTTP.
pub struct HttpRepository<D>
where
    D: DataInterchange,
{
    url: Url,
    client: Client,
    user_agent: String,
    metadata_prefix: Option<Vec<String>>,
    interchange: PhantomData<D>,
}

impl<D> HttpRepository<D>
where
    D: DataInterchange,
{
    /// Create a new repository with the given `Url` and `Client`.
    ///
    /// Callers *should* include a custom User-Agent prefix to help maintainers of TUF repositories
    /// keep track of which client versions exist in the field.
    ///
    /// The argument `metadata_prefix` is used provide an alternate path where metadata is stored on
    /// the repository. If `None`, this defaults to `/`. For example, if there is a TUF repository
    /// at `https://tuf.example.com/`, but all metadata is stored at `/meta/`, then passing the
    /// arg `Some("meta".into())` would cause `root.json` to be fetched from
    /// `https://tuf.example.com/meta/root.json`.
    pub fn new(
        url: Url,
        client: Client,
        user_agent_prefix: Option<String>,
        metadata_prefix: Option<Vec<String>>,
    ) -> Self {
        let user_agent = match user_agent_prefix {
            Some(ua) => format!("{} (rust-tuf/{})", ua, env!("CARGO_PKG_VERSION")),
            None => format!("rust-tuf/{}", env!("CARGO_PKG_VERSION")),
        };

        HttpRepository {
            url: url,
            client: client,
            user_agent: user_agent,
            metadata_prefix: metadata_prefix,
            interchange: PhantomData,
        }
    }

    fn get(&self, prefix: &Option<Vec<String>>, components: &[String]) -> Result<Response> {
        let mut headers = Headers::new();
        headers.set(UserAgent(self.user_agent.clone()));

        let mut url = self.url.clone();
        {
            let mut segments = url.path_segments_mut().map_err(|_| {
                Error::IllegalArgument(format!("URL was 'cannot-be-a-base': {:?}", self.url))
            })?;
            if let &Some(ref prefix) = prefix {
                segments.extend(prefix);
            }
            segments.extend(components);
        }

        let req = self.client.get(url.clone()).headers(headers);
        let resp = req.send()?;

        if !resp.status.is_success() {
            if resp.status == StatusCode::NotFound {
                Err(Error::NotFound)
            } else {
                Err(Error::Opaque(
                    format!("Error getting {:?}: {:?}", url, resp),
                ))
            }
        } else {
            Ok(resp)
        }
    }
}

impl<D> Repository<D> for HttpRepository<D>
where
    D: DataInterchange,
{
    type TargetRead = Response;

    fn initialize(&mut self) -> Result<()> {
        Ok(())
    }

    /// This always returns `Err` as storing over HTTP is not yet supported.
    fn store_metadata<M>(
        &mut self,
        _: &Role,
        _: &MetadataPath,
        _: &MetadataVersion,
        _: &SignedMetadata<D, M>,
    ) -> Result<()>
    where
        M: Metadata,
    {
        Err(Error::Opaque(
            "Http repo store metadata not implemented".to_string(),
        ))
    }

    fn fetch_metadata<M>(
        &mut self,
        role: &Role,
        meta_path: &MetadataPath,
        version: &MetadataVersion,
        max_size: &Option<usize>,
        min_bytes_per_second: u32,
        hash_data: Option<(&HashAlgorithm, HashValue)>,
    ) -> Result<SignedMetadata<D, M>>
    where
        M: Metadata,
    {
        Self::check::<M>(role, meta_path)?;

        let resp = self.get(
            &self.metadata_prefix,
            &meta_path.components::<D>(&version),
        )?;

        let read = SafeReader::new(
            resp,
            max_size.unwrap_or(::std::usize::MAX) as u64,
            min_bytes_per_second,
            hash_data,
        );
        Ok(D::from_reader(read)?)
    }

    /// This always returns `Err` as storing over HTTP is not yet supported.
    fn store_target<R>(&mut self, _: R, _: &TargetPath) -> Result<()>
    where
        R: Read,
    {
        Err(Error::Opaque(
            "Http repo store  not implemented".to_string(),
        ))
    }

    fn fetch_target(
        &mut self,
        target_path: &TargetPath,
        target_description: &TargetDescription,
        min_bytes_per_second: u32,
    ) -> Result<SafeReader<Self::TargetRead>> {
        let resp = self.get(&None, &target_path.components())?;
        let (alg, value) = crypto::hash_preference(target_description.hashes())?;
        Ok(SafeReader::new(
            resp,
            target_description.size(),
            min_bytes_per_second,
            Some((alg, value.clone())),
        ))
    }
}


/// An ephemeral repository contained solely in memory.
pub struct EphemeralRepository<D>
where
    D: DataInterchange,
{
    metadata: HashMap<(MetadataPath, MetadataVersion), Vec<u8>>,
    targets: HashMap<TargetPath, Vec<u8>>,
    interchange: PhantomData<D>,
}

impl<D> EphemeralRepository<D>
where
    D: DataInterchange,
{
    /// Create a new ephemercal repository.
    pub fn new() -> Self {
        EphemeralRepository {
            metadata: HashMap::new(),
            targets: HashMap::new(),
            interchange: PhantomData,
        }
    }
}

impl<D> Repository<D> for EphemeralRepository<D>
where
    D: DataInterchange,
{
    type TargetRead = Cursor<Vec<u8>>;

    fn initialize(&mut self) -> Result<()> {
        Ok(())
    }

    fn store_metadata<M>(
        &mut self,
        role: &Role,
        meta_path: &MetadataPath,
        version: &MetadataVersion,
        metadata: &SignedMetadata<D, M>,
    ) -> Result<()>
    where
        M: Metadata,
    {
        Self::check::<M>(role, meta_path)?;
        let mut buf = Vec::new();
        D::to_writer(&mut buf, metadata)?;
        let _ = self.metadata.insert(
            (meta_path.clone(), version.clone()),
            buf,
        );
        Ok(())
    }

    fn fetch_metadata<M>(
        &mut self,
        role: &Role,
        meta_path: &MetadataPath,
        version: &MetadataVersion,
        max_size: &Option<usize>,
        min_bytes_per_second: u32,
        hash_data: Option<(&HashAlgorithm, HashValue)>,
    ) -> Result<SignedMetadata<D, M>>
    where
        M: Metadata,
    {
        Self::check::<M>(role, meta_path)?;

        match self.metadata.get(&(meta_path.clone(), version.clone())) {
            Some(bytes) => {
                let reader = SafeReader::new(
                    &**bytes,
                    max_size.unwrap_or(::std::usize::MAX) as u64,
                    min_bytes_per_second,
                    hash_data,
                );
                D::from_reader(reader)
            }
            None => Err(Error::NotFound),
        }
    }

    fn store_target<R>(&mut self, mut read: R, target_path: &TargetPath) -> Result<()>
    where
        R: Read,
    {
        let mut buf = Vec::new();
        read.read_to_end(&mut buf)?;
        let _ = self.targets.insert(target_path.clone(), buf);
        Ok(())
    }

    fn fetch_target(
        &mut self,
        target_path: &TargetPath,
        target_description: &TargetDescription,
        min_bytes_per_second: u32,
    ) -> Result<SafeReader<Self::TargetRead>> {
        match self.targets.get(target_path) {
            Some(bytes) => {
                let cur = Cursor::new(bytes.clone());
                let (alg, value) = crypto::hash_preference(target_description.hashes())?;
                let read = SafeReader::new(
                    cur,
                    target_description.size(),
                    min_bytes_per_second,
                    Some((alg, value.clone())),
                );
                Ok(read)
            }
            None => Err(Error::NotFound),
        }
    }
}

#[cfg(test)]
mod test {
    use super::*;
    use tempdir::TempDir;
    use interchange::Json;

    #[test]
    fn ephemeral_repo_targets() {
        let mut repo = EphemeralRepository::<Json>::new();
        repo.initialize().unwrap();

        let data: &[u8] = b"like tears in the rain";
        let target_description = TargetDescription::from_reader(data, &[HashAlgorithm::Sha256])
            .unwrap();
        let path = TargetPath::new("batty".into()).unwrap();
        repo.store_target(data, &path).unwrap();

        let mut read = repo.fetch_target(&path, &target_description, 0).unwrap();
        let mut buf = Vec::new();
        read.read_to_end(&mut buf).unwrap();
        assert_eq!(buf.as_slice(), data);

        let bad_data: &[u8] = b"you're in a desert";
        repo.store_target(bad_data, &path).unwrap();
        let mut read = repo.fetch_target(&path, &target_description, 0).unwrap();
        assert!(read.read_to_end(&mut buf).is_err());
    }

    #[test]
    fn file_system_repo_targets() {
        let temp_dir = TempDir::new("rust-tuf").unwrap();
        let mut repo = FileSystemRepository::<Json>::new(temp_dir.path().to_path_buf());
        repo.initialize().unwrap();

        let data: &[u8] = b"like tears in the rain";
        let target_description = TargetDescription::from_reader(data, &[HashAlgorithm::Sha256])
            .unwrap();
        let path = TargetPath::new("batty".into()).unwrap();
        repo.store_target(data, &path).unwrap();
        assert!(temp_dir.path().join("targets").join("batty").exists());

        let mut read = repo.fetch_target(&path, &target_description, 0).unwrap();
        let mut buf = Vec::new();
        read.read_to_end(&mut buf).unwrap();
        assert_eq!(buf.as_slice(), data);

        let bad_data: &[u8] = b"you're in a desert";
        repo.store_target(bad_data, &path).unwrap();
        let mut read = repo.fetch_target(&path, &target_description, 0).unwrap();
        assert!(read.read_to_end(&mut buf).is_err());
    }
}