asic-e 0.1.0

//! In-memory representation of an ASiC-E container.

use std::io::{Cursor, Read, Seek, Write};

use zip::write::SimpleFileOptions;
use zip::{CompressionMethod, ZipArchive, ZipWriter};

use crate::{manifest, LibError, Result, MIMETYPE};

/// A data file stored in the container.
#[derive(Debug, Clone)]
pub struct DataFile {
    /// File name inside the archive.
    pub name: String,
    /// Media type recorded in the manifest.
    pub mime_type: String,
    /// Raw file content.
    pub content: Vec<u8>,
}

/// A signature document (`META-INF/*signatures*.xml`).
#[derive(Debug, Clone)]
pub struct SignatureFile {
    /// Document name inside the archive.
    pub name: String,
    /// The signature document as opaque XML.
    pub xml: String,
}

/// Policy for `Container::open_with`.
#[derive(Debug, Clone)]
pub struct OpenOptions {
    /// Require the `mimetype` entry to be present.
    ///
    /// Optional in EN 319 162-1 but additional profiles (e.g. BDOC) may require it.
    /// Defaults to `false`.
    pub require_mimetype: bool,
}

impl Default for OpenOptions {
    fn default() -> Self {
        Self {
            require_mimetype: false,
        }
    }
}

/// An ASiC-E container held in memory.
#[derive(Debug, Default)]
pub struct Container {
    data_files: Vec<DataFile>,
    signatures: Vec<SignatureFile>,
    /// Potential structural anomalies found while opening a container.
    warnings: Vec<String>,
}

impl Container {
    /// Create an empty container.
    pub fn new() -> Self {
        Self::default()
    }

    /// Data files in the container.
    pub fn data_files(&self) -> &[DataFile] {
        &self.data_files
    }

    /// Signature documents in the container.
    pub fn signatures(&self) -> &[SignatureFile] {
        &self.signatures
    }

    /// Structural warnings collected when opening the container.
    pub fn warnings(&self) -> &[String] {
        &self.warnings
    }

    /// Add a data file.
    ///
    /// # Errors
    /// If the name is not relative, a duplicate, or reserved.
    pub fn add_file(
        &mut self,
        name: impl Into<String>,
        mime_type: impl Into<String>,
        content: Vec<u8>,
    ) -> Result<()> {
        let name = name.into();
        validate_entry_name(&name)?;
        if self.data_files.iter().any(|f| f.name == name) {
            return Err(LibError::Container(format!("duplicate file name: {name}")));
        }
        self.data_files.push(DataFile {
            name,
            mime_type: mime_type.into(),
            content,
        });
        Ok(())
    }

    /// Append a signature document.
    ///
    /// The entry name is assigned automatically as `META-INF/signaturesN.xml`,
    /// using the first free index `N`.
    pub fn add_signature_xml(&mut self, xml: String) -> &SignatureFile {
        let mut n = self.signatures.len();
        let name = loop {
            let candidate = format!("META-INF/signatures{n}.xml");
            if !self.signatures.iter().any(|s| s.name == candidate) {
                break candidate;
            }
            n += 1;
        };
        self.signatures.push(SignatureFile { name, xml });
        self.signatures.last().expect("a signature should exist")
    }

    /// Open a container from any seekable reader, using default `OpenOptions`.
    pub fn open<R: Read + Seek>(reader: R) -> Result<Self> {
        Self::open_with(reader, &OpenOptions::default())
    }

    /// Open a container from any seekable reader under an explicit policy.
    pub fn open_with<R: Read + Seek>(reader: R, opts: &OpenOptions) -> Result<Self> {
        let mut zip = ZipArchive::new(reader)?;
        let mut container = Container::default();

        let mut names: Vec<String> = Vec::with_capacity(zip.len());
        for i in 0..zip.len() {
            names.push(zip.by_index(i)?.name().to_owned());
        }

        // EN 319 162-1 v1.1.1, A.1. If present, the mimetype shall
        // - be the first file in the ASiC container
        // - not be compressed
        // BDOC mandates the presence of the mimetype file.
        let mimetype_present = names.iter().any(|n| n == "mimetype");
        if let Some(n) = names.first() {
            if n == "mimetype" {
                let entry = zip.by_index(0)?;
                if entry.compression() != CompressionMethod::Stored {
                    container.warnings.push("'mimetype' is compressed".into());
                }
            } else if mimetype_present {
                container
                    .warnings
                    .push("'mimetype' is not the first zip entry".into());
            }
        }
        if mimetype_present {
            let mimetype = read_entry(&mut zip, "mimetype")?;
            let mimetype = String::from_utf8_lossy(&mimetype);
            if mimetype.trim() != MIMETYPE {
                return Err(LibError::Container(format!(
                    "unexpected container mime type: {}",
                    mimetype.trim()
                )));
            }
        } else if opts.require_mimetype {
            return Err(LibError::Container("missing mimetype entry".into()));
        } else {
            container
                .warnings
                .push("container has no mimetype entry".into());
        }

        // EN 319 162-1 V1.1.1 § 5.3.3 (Table 5)
        // 'META-INF/manifest.xml shall be present' for ASiC-E with XAdES signatures
        let manifest_types = match read_entry(&mut zip, "META-INF/manifest.xml") {
            Ok(bytes) => manifest::parse(&bytes)?,
            Err(_) => {
                return Err(LibError::Container(
                    "container has no META-INF/manifest.xml".into(),
                ));
            }
        };

        for name in &names {
            if name == "mimetype" || name.ends_with('/') {
                continue;
            }
            let bytes = read_entry(&mut zip, name)?;
            if let Some(rest) = name.strip_prefix("META-INF/") {
                if is_signature_entry(rest) {
                    container.signatures.push(SignatureFile {
                        name: name.clone(),
                        xml: String::from_utf8(bytes)
                            .map_err(|_| LibError::Xml(format!("{name} is not valid UTF-8")))?,
                    });
                }
                // '4.4.3.2 Note 5' of EN 319 162-1 v1.1.1:
                // Other file objects in META-INF/ need not be parsed and interpreted for the
                // purpose of the ASiC container validation, provided that they do not contain the
                // string "signature" or "timestamp" or "manifest" or "container.xml".
                // TODO: implement this check, and the processing of the other allowed files.
                continue;
            }
            let mime_type = manifest_types
                .iter()
                .find(|(n, _)| n == name)
                .map(|(_, m)| m.clone())
                .ok_or_else(|| {
                    LibError::Container(format!("missing MIME type in manifest for {name}"))
                })?;
            container.data_files.push(DataFile {
                name: name.clone(),
                mime_type,
                content: bytes,
            });
        }

        if container.data_files.is_empty() {
            return Err(LibError::Container("container has no data files".into()));
        }
        Ok(container)
    }

    /// Open a container from a byte buffer.
    pub fn from_bytes(bytes: &[u8]) -> Result<Self> {
        Self::open(Cursor::new(bytes))
    }

    /// Open a container file from disk.
    pub fn open_file(path: impl AsRef<std::path::Path>) -> Result<Self> {
        Self::open(std::fs::File::open(path)?)
    }

    /// Open a container file from disk under an explicit policy.
    pub fn open_file_with(path: impl AsRef<std::path::Path>, opts: &OpenOptions) -> Result<Self> {
        Self::open_with(std::fs::File::open(path)?, opts)
    }

    fn write_to<W: Write + Seek>(&self, writer: W) -> Result<()> {
        if self.data_files.is_empty() {
            return Err(LibError::Container("container has no data files".into()));
        }
        let mut zip = ZipWriter::new(writer);

        zip.start_file(
            "mimetype",
            SimpleFileOptions::default().compression_method(CompressionMethod::Stored),
        )?;
        zip.write_all(MIMETYPE.as_bytes())?;

        let deflated = SimpleFileOptions::default().compression_method(CompressionMethod::Deflated);
        for file in &self.data_files {
            zip.start_file(&file.name, deflated)?;
            zip.write_all(&file.content)?;
        }

        zip.start_file("META-INF/manifest.xml", deflated)?;
        zip.write_all(&manifest::build(&self.data_files))?;

        for sig in &self.signatures {
            zip.start_file(&sig.name, deflated)?;
            zip.write_all(sig.xml.as_bytes())?;
        }

        zip.finish()?;
        Ok(())
    }

    /// Serialize the container to a byte buffer.
    pub fn to_bytes(&self) -> Result<Vec<u8>> {
        let mut buf = Cursor::new(Vec::new());
        self.write_to(&mut buf)?;
        Ok(buf.into_inner())
    }

    /// Write the container to a file on disk.
    pub fn save(&self, path: impl AsRef<std::path::Path>) -> Result<()> {
        self.write_to(std::fs::File::create(path)?)
    }
}

fn read_entry<R: Read + Seek>(zip: &mut ZipArchive<R>, name: &str) -> Result<Vec<u8>> {
    let mut entry = zip
        .by_name(name)
        .map_err(|_| LibError::Container(format!("missing zip entry: {name}")))?;
    let mut buf = Vec::with_capacity(entry.size() as usize);
    entry.read_to_end(&mut buf)?;
    Ok(buf)
}

fn validate_entry_name(name: &str) -> Result<()> {
    if name.is_empty() {
        return Err(LibError::Container("file name must not be empty".into()));
    }
    if name == "mimetype" || name.starts_with("META-INF/") {
        return Err(LibError::Container(format!("reserved entry name: {name}")));
    }
    if name.starts_with('/') || name.split('/').any(|part| part == ".." || part.is_empty()) {
        return Err(LibError::Container(format!(
            "file name must be a clean relative path: {name}"
        )));
    }
    Ok(())
}

fn is_signature_entry(meta_inf_rest: &str) -> bool {
    // See '4.4.3.2 2)' of EN 319 162-1 v1.1.1
    meta_inf_rest.contains("signatures") && meta_inf_rest.ends_with(".xml")
}