1 files changed, 152 insertions, 13 deletions

diff --git a/src/chunk.rs b/src/chunk.rs
index 4917b60..a6abad3 100644
--- a/src/chunk.rs
+++ b/src/chunk.rs
@@ -1,60 +1,199 @@
+//! Chunks of data.
+
 use crate::chunkid::ChunkId;
+use crate::chunkmeta::ChunkMeta;
+use crate::label::Label;
 use serde::{Deserialize, Serialize};
 use std::default::Default;
 
-/// Store an arbitrary chunk of data.
-///
-/// The data is just arbitrary binary data.
+/// An arbitrary chunk of arbitrary binary data.
 ///
 /// A chunk also contains its associated metadata, except its
-/// identifier.
-#[derive(Debug, Clone, Serialize, Deserialize)]
+/// identifier, so that it's easy to keep the data and metadata
+/// together. The identifier is used to find the chunk, and it's
+/// assigned by the server when the chunk is uploaded, so it's not
+/// stored in the chunk itself.
+#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq)]
 pub struct DataChunk {
     data: Vec<u8>,
+    meta: ChunkMeta,
 }
 
 impl DataChunk {
-    /// Construct a new chunk.
-    pub fn new(data: Vec<u8>) -> Self {
-        Self { data }
+    /// Create a new chunk.
+    pub fn new(data: Vec<u8>, meta: ChunkMeta) -> Self {
+        Self { data, meta }
     }
 
     /// Return a chunk's data.
     pub fn data(&self) -> &[u8] {
         &self.data
     }
+
+    /// Return a chunk's metadata.
+    pub fn meta(&self) -> &ChunkMeta {
+        &self.meta
+    }
 }
 
+/// A chunk representing a backup generation.
+///
+/// A generation chunk lists all the data chunks for the SQLite file
+/// with the backup's metadata. It's different from a normal data
+/// chunk so that we can do things that make no sense to a data chunk.
+/// Generation chunks can be converted into or created from data
+/// chunks, for uploading to or downloading from the server.
 #[derive(Default, Debug, Serialize, Deserialize)]
 pub struct GenerationChunk {
     chunk_ids: Vec<ChunkId>,
 }
 
+/// All the errors that may be returned for `GenerationChunk` operations.
+#[derive(Debug, thiserror::Error)]
+pub enum GenerationChunkError {
+    /// Error converting text from UTF8.
+    #[error(transparent)]
+    Utf8Error(#[from] std::str::Utf8Error),
+
+    /// Error parsing JSON as chunk metadata.
+    #[error("failed to parse JSON: {0}")]
+    JsonParse(serde_json::Error),
+
+    /// Error generating JSON from chunk metadata.
+    #[error("failed to serialize to JSON: {0}")]
+    JsonGenerate(serde_json::Error),
+}
+
 impl GenerationChunk {
+    /// Create a new backup generation chunk from metadata chunk ids.
     pub fn new(chunk_ids: Vec<ChunkId>) -> Self {
         Self { chunk_ids }
     }
 
-    pub fn from_data_chunk(chunk: &DataChunk) -> anyhow::Result<Self> {
+    /// Create a new backup generation chunk from a data chunk.
+    pub fn from_data_chunk(chunk: &DataChunk) -> Result<Self, GenerationChunkError> {
         let data = chunk.data();
         let data = std::str::from_utf8(data)?;
-        Ok(serde_json::from_str(data)?)
+        serde_json::from_str(data).map_err(GenerationChunkError::JsonParse)
     }
 
+    /// Does the generation chunk contain any metadata chunks?
     pub fn is_empty(&self) -> bool {
         self.chunk_ids.is_empty()
     }
 
+    /// How many metadata chunks does generation chunk contain?
     pub fn len(&self) -> usize {
         self.chunk_ids.len()
     }
 
+    /// Return iterator over the metadata chunk identifiers.
     pub fn chunk_ids(&self) -> impl Iterator<Item = &ChunkId> {
         self.chunk_ids.iter()
     }
 
-    pub fn to_data_chunk(&self) -> anyhow::Result<DataChunk> {
-        let json = serde_json::to_string(self)?;
-        Ok(DataChunk::new(json.as_bytes().to_vec()))
+    /// Convert generation chunk to a data chunk.
+    pub fn to_data_chunk(&self) -> Result<DataChunk, GenerationChunkError> {
+        let json: String =
+            serde_json::to_string(self).map_err(GenerationChunkError::JsonGenerate)?;
+        let bytes = json.as_bytes().to_vec();
+        let checksum = Label::sha256(&bytes);
+        let meta = ChunkMeta::new(&checksum);
+        Ok(DataChunk::new(bytes, meta))
+    }
+}
+
+/// A client trust root chunk.
+///
+/// This chunk contains all per-client backup information. As long as
+/// this chunk can be trusted, everything it links to can also be
+/// trusted, thanks to cryptographic signatures.
+#[derive(Debug, Serialize, Deserialize)]
+pub struct ClientTrust {
+    client_name: String,
+    previous_version: Option<ChunkId>,
+    timestamp: String,
+    backups: Vec<ChunkId>,
+}
+
+/// All the errors that may be returned for `ClientTrust` operations.
+#[derive(Debug, thiserror::Error)]
+pub enum ClientTrustError {
+    /// Error converting text from UTF8.
+    #[error(transparent)]
+    Utf8Error(#[from] std::str::Utf8Error),
+
+    /// Error parsing JSON as chunk metadata.
+    #[error("failed to parse JSON: {0}")]
+    JsonParse(serde_json::Error),
+
+    /// Error generating JSON from chunk metadata.
+    #[error("failed to serialize to JSON: {0}")]
+    JsonGenerate(serde_json::Error),
+}
+
+impl ClientTrust {
+    /// Create a new ClientTrust object.
+    pub fn new(
+        name: &str,
+        previous_version: Option<ChunkId>,
+        timestamp: String,
+        backups: Vec<ChunkId>,
+    ) -> Self {
+        Self {
+            client_name: name.to_string(),
+            previous_version,
+            timestamp,
+            backups,
+        }
+    }
+
+    /// Return client name.
+    pub fn client_name(&self) -> &str {
+        &self.client_name
+    }
+
+    /// Return id of previous version, if any.
+    pub fn previous_version(&self) -> Option<ChunkId> {
+        self.previous_version.clone()
+    }
+
+    /// Return timestamp.
+    pub fn timestamp(&self) -> &str {
+        &self.timestamp
+    }
+
+    /// Return list of all backup generations known.
+    pub fn backups(&self) -> &[ChunkId] {
+        &self.backups
+    }
+
+    /// Append a backup generation to the list.
+    pub fn append_backup(&mut self, id: &ChunkId) {
+        self.backups.push(id.clone());
+    }
+
+    /// Update for new upload.
+    ///
+    /// This needs to happen every time the chunk is updated so that
+    /// the timestamp gets updated.
+    pub fn finalize(&mut self, timestamp: String) {
+        self.timestamp = timestamp;
+    }
+
+    /// Convert generation chunk to a data chunk.
+    pub fn to_data_chunk(&self) -> Result<DataChunk, ClientTrustError> {
+        let json: String = serde_json::to_string(self).map_err(ClientTrustError::JsonGenerate)?;
+        let bytes = json.as_bytes().to_vec();
+        let checksum = Label::literal("client-trust");
+        let meta = ChunkMeta::new(&checksum);
+        Ok(DataChunk::new(bytes, meta))
+    }
+
+    /// Create a new ClientTrust from a data chunk.
+    pub fn from_data_chunk(chunk: &DataChunk) -> Result<Self, ClientTrustError> {
+        let data = chunk.data();
+        let data = std::str::from_utf8(data)?;
+        serde_json::from_str(data).map_err(ClientTrustError::JsonParse)
     }
 }