feat(patch): 补齐通用补丁引擎基础

实现 Binary、JSON、Text patch 与通用 manifest 校验基础。

验证：cargo test -p bat-patch --locked；cargo clippy -p bat-patch --all-targets --locked -- -D warnings。

crates/bat-patch/src/binary.rs

@@ -1,13 +1,145 @@
-//! Binary Patch 模块占位
+//! Deterministic binary hunk patch.
 
-/// Binary Patch 应用（尚未实现）。
+use crate::PatchError;
+use serde::{Deserialize, Serialize};
+
+/// Current binary patch schema version.
+pub const BINARY_PATCH_VERSION: u32 = 1;
+
+/// Binary patch made of deterministic copy/insert hunks.
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct BinaryPatch {
+    /// Patch schema version.
+    pub version: u32,
+    /// Expected BLAKE3 hash of the source bytes.
+    pub source_blake3: String,
+    /// Expected BLAKE3 hash of the target bytes.
+    pub target_blake3: String,
+    /// Source byte length.
+    pub source_size: u64,
+    /// Target byte length.
+    pub target_size: u64,
+    /// Ordered hunks.
+    pub hunks: Vec<BinaryPatchHunk>,
+}
+
+/// One binary patch hunk.
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(tag = "kind", rename_all = "snake_case")]
+pub enum BinaryPatchHunk {
+    /// Copy a byte range from the source.
+    Copy {
+        /// Source offset.
+        offset: u64,
+        /// Number of bytes to copy.
+        length: u64,
+    },
+    /// Insert literal bytes.
+    Insert {
+        /// Literal bytes.
+        bytes: Vec<u8>,
+    },
+}
+
+/// Creates a deterministic hunk patch.
 ///
-/// 返回 [`crate::PatchError::ApplyFailed`] 而非空结果，避免调用方把未实现的
-/// 占位当成一次成功的补丁应用。
-pub fn apply_patch(_old: &[u8], _patch: &[u8]) -> crate::Result<Vec<u8>> {
-    Err(crate::PatchError::ApplyFailed(
-        "binary patch 尚未实现".to_string(),
+/// The first implementation optimizes for correctness and stable output. It
+/// emits copy hunks for equal runs and insert hunks for changed runs; more
+/// compact suffix/prefix matching can be added later without changing the
+/// manifest/integrity contract.
+pub fn diff(old: &[u8], new: &[u8]) -> BinaryPatch {
+    let mut hunks = Vec::new();
+    let mut index = 0usize;
+    while index < new.len() {
+        if index < old.len() && old[index] == new[index] {
+            let start = index;
+            while index < new.len() && index < old.len() && old[index] == new[index] {
+                index += 1;
+            }
+            hunks.push(BinaryPatchHunk::Copy {
+                offset: start as u64,
+                length: (index - start) as u64,
+            });
+            continue;
+        }
+
+        let start = index;
+        while index < new.len() && (index >= old.len() || old[index] != new[index]) {
+            index += 1;
+        }
+        hunks.push(BinaryPatchHunk::Insert {
+            bytes: new[start..index].to_vec(),
+        });
+    }
+
+    BinaryPatch {
+        version: BINARY_PATCH_VERSION,
+        source_blake3: blake3_hex(old),
+        target_blake3: blake3_hex(new),
+        source_size: old.len() as u64,
+        target_size: new.len() as u64,
+        hunks,
+    }
+}
+
+/// Applies a structured binary patch.
+pub fn apply_binary_patch(old: &[u8], patch: &BinaryPatch) -> crate::Result<Vec<u8>> {
+    if patch.version != BINARY_PATCH_VERSION {
+        return Err(PatchError::ApplyFailed(format!(
+            "unsupported binary patch version {}",
+            patch.version
+        )));
+    }
+    if patch.source_size != old.len() as u64 || patch.source_blake3 != blake3_hex(old) {
+        return Err(PatchError::ApplyFailed(
+            "binary patch source integrity mismatch".to_string(),
+        ));
+    }
+
+    let target_capacity = usize::try_from(patch.target_size)
+        .map_err(|_| PatchError::ApplyFailed("binary patch target too large".to_string()))?;
+    let mut output = Vec::with_capacity(target_capacity);
+    for hunk in &patch.hunks {
+        match hunk {
+            BinaryPatchHunk::Copy { offset, length } => {
+                let start = usize::try_from(*offset).map_err(|_| {
+                    PatchError::ApplyFailed("binary patch copy offset overflow".to_string())
+                })?;
+                let length = usize::try_from(*length).map_err(|_| {
+                    PatchError::ApplyFailed("binary patch copy length overflow".to_string())
+                })?;
+                let end = start.checked_add(length).ok_or_else(|| {
+                    PatchError::ApplyFailed("binary patch copy range overflow".to_string())
+                })?;
+                let bytes = old.get(start..end).ok_or_else(|| {
+                    PatchError::ApplyFailed(format!(
+                        "binary patch copy range {start}..{end} exceeds source {}",
+                        old.len()
                     ))
+                })?;
+                output.extend_from_slice(bytes);
+            }
+            BinaryPatchHunk::Insert { bytes } => output.extend_from_slice(bytes),
+        }
+    }
+
+    if output.len() as u64 != patch.target_size || blake3_hex(&output) != patch.target_blake3 {
+        return Err(PatchError::ApplyFailed(
+            "binary patch target integrity mismatch".to_string(),
+        ));
+    }
+    Ok(output)
+}
+
+/// Serializes and applies a binary patch.
+pub fn apply_patch(old: &[u8], patch: &[u8]) -> crate::Result<Vec<u8>> {
+    let patch: BinaryPatch = serde_json::from_slice(patch)
+        .map_err(|error| PatchError::ApplyFailed(format!("invalid binary patch JSON: {error}")))?;
+    apply_binary_patch(old, &patch)
+}
+
+fn blake3_hex(bytes: &[u8]) -> String {
+    blake3::hash(bytes).to_hex().to_string()
 }
 
 #[cfg(test)]
@@ -15,8 +147,24 @@ mod tests {
     use super::*;
 
     #[test]
-    fn apply_patch_reports_not_implemented() {
-        let error = apply_patch(b"old", b"patch").unwrap_err();
+    fn binary_patch_round_trips_changed_bytes() {
+        let old = b"abcdef012345";
+        let new = b"abcXYZ012345!";
+        let patch = diff(old, new);
+        let patch_json = serde_json::to_vec(&patch).unwrap();
+
+        assert_eq!(apply_binary_patch(old, &patch).unwrap(), new);
+        assert_eq!(apply_patch(old, &patch_json).unwrap(), new);
+        assert!(patch
+            .hunks
+            .iter()
+            .any(|hunk| matches!(hunk, BinaryPatchHunk::Insert { .. })));
+    }
+
+    #[test]
+    fn binary_patch_rejects_wrong_source() {
+        let patch = diff(b"old", b"new");
+        let error = apply_binary_patch(b"bad", &patch).unwrap_err();
         assert!(matches!(error, crate::PatchError::ApplyFailed(_)));
     }
 }

crates/bat-patch/src/json.rs

@@ -1,22 +1,366 @@
-//! JSON Patch 模块占位
+//! RFC 6902 JSON Patch support.
 
-/// JSON Patch 应用（尚未实现）。
+use crate::PatchError;
+use serde::{Deserialize, Serialize};
+use serde_json::Value;
+
+/// One RFC 6902 JSON Patch operation.
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+#[serde(tag = "op", rename_all = "lowercase")]
+pub enum JsonPatchOperation {
+    /// Add a value at the target JSON Pointer.
+    Add {
+        /// Target JSON Pointer.
+        path: String,
+        /// Value to insert.
+        value: Value,
+    },
+    /// Remove the value at the target JSON Pointer.
+    Remove {
+        /// Target JSON Pointer.
+        path: String,
+    },
+    /// Replace the value at the target JSON Pointer.
+    Replace {
+        /// Target JSON Pointer.
+        path: String,
+        /// Replacement value.
+        value: Value,
+    },
+    /// Move a value from one JSON Pointer to another.
+    Move {
+        /// Source JSON Pointer.
+        from: String,
+        /// Target JSON Pointer.
+        path: String,
+    },
+    /// Copy a value from one JSON Pointer to another.
+    Copy {
+        /// Source JSON Pointer.
+        from: String,
+        /// Target JSON Pointer.
+        path: String,
+    },
+    /// Assert that a JSON Pointer currently contains a value.
+    Test {
+        /// Target JSON Pointer.
+        path: String,
+        /// Expected value.
+        value: Value,
+    },
+}
+
+/// Applies an RFC 6902 JSON Patch document to a JSON document string.
+pub fn apply_json_patch(doc: &str, patch: &str) -> crate::Result<String> {
+    let mut document: Value = serde_json::from_str(doc)
+        .map_err(|error| PatchError::ApplyFailed(format!("invalid JSON document: {error}")))?;
+    let operations: Vec<JsonPatchOperation> = serde_json::from_str(patch)
+        .map_err(|error| PatchError::ApplyFailed(format!("invalid JSON patch: {error}")))?;
+    apply_json_patch_value(&mut document, &operations)?;
+    serde_json::to_string(&document)
+        .map_err(|error| PatchError::ApplyFailed(format!("failed to serialize JSON: {error}")))
+}
+
+/// Applies parsed JSON Patch operations to a JSON value.
 ///
-/// 返回 [`crate::PatchError::ApplyFailed`] 而非空字符串，避免调用方把未实现的
-/// 占位当成一次成功的补丁应用。
-pub fn apply_json_patch(_doc: &str, _patch: &str) -> crate::Result<String> {
-    Err(crate::PatchError::ApplyFailed(
-        "json patch 尚未实现".to_string(),
-    ))
+/// Each operation is applied atomically: when one operation fails, the document
+/// remains at the state produced by the previous successful operation.
+pub fn apply_json_patch_value(
+    document: &mut Value,
+    operations: &[JsonPatchOperation],
+) -> crate::Result<()> {
+    for operation in operations {
+        let mut next = document.clone();
+        apply_operation(&mut next, operation)?;
+        *document = next;
+    }
+    Ok(())
+}
+
+fn apply_operation(document: &mut Value, operation: &JsonPatchOperation) -> crate::Result<()> {
+    match operation {
+        JsonPatchOperation::Add { path, value } => add_value(document, path, value.clone()),
+        JsonPatchOperation::Remove { path } => remove_value(document, path).map(drop),
+        JsonPatchOperation::Replace { path, value } => replace_value(document, path, value.clone()),
+        JsonPatchOperation::Move { from, path } => {
+            if from == path {
+                return Ok(());
+            }
+            let value = get_value(document, from)?.clone();
+            remove_value(document, from)?;
+            add_value(document, path, value)
+        }
+        JsonPatchOperation::Copy { from, path } => {
+            let value = get_value(document, from)?.clone();
+            add_value(document, path, value)
+        }
+        JsonPatchOperation::Test { path, value } => {
+            let actual = get_value(document, path)?;
+            if actual == value {
+                Ok(())
+            } else {
+                Err(failed(format!(
+                    "JSON patch test failed at {path}: expected {value}, actual {actual}"
+                )))
+            }
+        }
+    }
+}
+
+fn add_value(document: &mut Value, path: &str, value: Value) -> crate::Result<()> {
+    let tokens = parse_json_pointer(path)?;
+    if tokens.is_empty() {
+        *document = value;
+        return Ok(());
+    }
+
+    let key = tokens.last().expect("checked non-empty").clone();
+    let parent = get_mut_by_tokens(document, &tokens[..tokens.len() - 1])?;
+    match parent {
+        Value::Object(map) => {
+            map.insert(key, value);
+            Ok(())
+        }
+        Value::Array(items) => {
+            if key == "-" {
+                items.push(value);
+                return Ok(());
+            }
+            let index = parse_array_index(&key, items.len(), true)?;
+            items.insert(index, value);
+            Ok(())
+        }
+        other => Err(failed(format!(
+            "cannot add JSON patch value below non-container value {other}"
+        ))),
+    }
+}
+
+fn remove_value(document: &mut Value, path: &str) -> crate::Result<Value> {
+    let tokens = parse_json_pointer(path)?;
+    if tokens.is_empty() {
+        return Ok(std::mem::take(document));
+    }
+
+    let key = tokens.last().expect("checked non-empty").clone();
+    let parent = get_mut_by_tokens(document, &tokens[..tokens.len() - 1])?;
+    match parent {
+        Value::Object(map) => map
+            .remove(&key)
+            .ok_or_else(|| failed(format!("JSON patch path {path} does not exist"))),
+        Value::Array(items) => {
+            let index = parse_array_index(&key, items.len(), false)?;
+            Ok(items.remove(index))
+        }
+        other => Err(failed(format!(
+            "cannot remove JSON patch value below non-container value {other}"
+        ))),
+    }
+}
+
+fn replace_value(document: &mut Value, path: &str, value: Value) -> crate::Result<()> {
+    let tokens = parse_json_pointer(path)?;
+    if tokens.is_empty() {
+        *document = value;
+        return Ok(());
+    }
+
+    let key = tokens.last().expect("checked non-empty").clone();
+    let parent = get_mut_by_tokens(document, &tokens[..tokens.len() - 1])?;
+    match parent {
+        Value::Object(map) => {
+            let slot = map
+                .get_mut(&key)
+                .ok_or_else(|| failed(format!("JSON patch path {path} does not exist")))?;
+            *slot = value;
+            Ok(())
+        }
+        Value::Array(items) => {
+            let index = parse_array_index(&key, items.len(), false)?;
+            items[index] = value;
+            Ok(())
+        }
+        other => Err(failed(format!(
+            "cannot replace JSON patch value below non-container value {other}"
+        ))),
+    }
+}
+
+fn get_value<'a>(document: &'a Value, path: &str) -> crate::Result<&'a Value> {
+    let tokens = parse_json_pointer(path)?;
+    let mut current = document;
+    for token in &tokens {
+        current = match current {
+            Value::Object(map) => map
+                .get(token)
+                .ok_or_else(|| failed(format!("JSON patch path {path} does not exist")))?,
+            Value::Array(items) => {
+                let index = parse_array_index(token, items.len(), false)?;
+                items
+                    .get(index)
+                    .ok_or_else(|| failed(format!("JSON patch path {path} does not exist")))?
+            }
+            other => {
+                return Err(failed(format!(
+                    "cannot traverse JSON patch path {path} through non-container value {other}"
+                )))
+            }
+        };
+    }
+    Ok(current)
+}
+
+fn get_mut_by_tokens<'a>(
+    document: &'a mut Value,
+    tokens: &[String],
+) -> crate::Result<&'a mut Value> {
+    let mut current = document;
+    for token in tokens {
+        current = match current {
+            Value::Object(map) => map
+                .get_mut(token)
+                .ok_or_else(|| failed(format!("JSON patch path segment {token} does not exist")))?,
+            Value::Array(items) => {
+                let index = parse_array_index(token, items.len(), false)?;
+                items.get_mut(index).ok_or_else(|| {
+                    failed(format!("JSON patch path segment {token} does not exist"))
+                })?
+            }
+            other => {
+                return Err(failed(format!(
+                    "cannot traverse JSON patch path through non-container value {other}"
+                )))
+            }
+        };
+    }
+    Ok(current)
+}
+
+fn parse_array_index(token: &str, len: usize, allow_end: bool) -> crate::Result<usize> {
+    if token.is_empty() || token == "-" {
+        return Err(failed(format!("invalid JSON patch array index {token}")));
+    }
+    let index = token
+        .parse::<usize>()
+        .map_err(|_| failed(format!("invalid JSON patch array index {token}")))?;
+    let max = if allow_end {
+        len
+    } else {
+        len.checked_sub(1)
+            .ok_or_else(|| failed("JSON patch array index exceeds empty array".to_string()))?
+    };
+    if index > max {
+        return Err(failed(format!(
+            "JSON patch array index {index} exceeds length {len}"
+        )));
+    }
+    Ok(index)
+}
+
+fn parse_json_pointer(pointer: &str) -> crate::Result<Vec<String>> {
+    if pointer.is_empty() {
+        return Ok(Vec::new());
+    }
+    if !pointer.starts_with('/') {
+        return Err(failed(format!(
+            "JSON patch pointer must be empty or start with '/': {pointer}"
+        )));
+    }
+    pointer[1..]
+        .split('/')
+        .map(decode_json_pointer_token)
+        .collect()
+}
+
+fn decode_json_pointer_token(token: &str) -> crate::Result<String> {
+    let mut decoded = String::with_capacity(token.len());
+    let mut chars = token.chars();
+    while let Some(character) = chars.next() {
+        if character != '~' {
+            decoded.push(character);
+            continue;
+        }
+        match chars.next() {
+            Some('0') => decoded.push('~'),
+            Some('1') => decoded.push('/'),
+            Some(other) => {
+                return Err(failed(format!(
+                    "invalid JSON patch pointer escape ~{other}"
+                )))
+            }
+            None => return Err(failed("invalid JSON patch pointer escape ~".to_string())),
+        }
+    }
+    Ok(decoded)
+}
+
+fn failed(message: String) -> PatchError {
+    PatchError::ApplyFailed(message)
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
+    use serde_json::json;
 
     #[test]
-    fn apply_json_patch_reports_not_implemented() {
-        let error = apply_json_patch("{}", "[]").unwrap_err();
+    fn apply_json_patch_handles_all_core_operations() {
+        let document = r#"{"name":"alice","items":["a","b"],"meta":{"keep":true}}"#;
+        let patch = r#"[
+            {"op":"test","path":"/meta/keep","value":true},
+            {"op":"add","path":"/items/-","value":"c"},
+            {"op":"replace","path":"/name","value":"bob"},
+            {"op":"copy","from":"/meta","path":"/copied"},
+            {"op":"move","from":"/items/0","path":"/first"},
+            {"op":"remove","path":"/meta/keep"}
+        ]"#;
+
+        let output = apply_json_patch(document, patch).unwrap();
+        let value: Value = serde_json::from_str(&output).unwrap();
+
+        assert_eq!(value["name"], json!("bob"));
+        assert_eq!(value["items"], json!(["b", "c"]));
+        assert_eq!(value["first"], json!("a"));
+        assert_eq!(value["copied"], json!({"keep": true}));
+        assert_eq!(value["meta"], json!({}));
+    }
+
+    #[test]
+    fn apply_json_patch_supports_pointer_escapes() {
+        let document = r#"{"a/b":{"tilde~key":1}}"#;
+        let patch = r#"[{"op":"replace","path":"/a~1b/tilde~0key","value":2}]"#;
+
+        let output = apply_json_patch(document, patch).unwrap();
+        let value: Value = serde_json::from_str(&output).unwrap();
+
+        assert_eq!(value["a/b"]["tilde~key"], json!(2));
+    }
+
+    #[test]
+    fn apply_json_patch_rejects_failed_test_without_mutating_value() {
+        let mut value = json!({"enabled": true});
+        let operations = vec![
+            JsonPatchOperation::Add {
+                path: "/count".to_string(),
+                value: json!(1),
+            },
+            JsonPatchOperation::Test {
+                path: "/enabled".to_string(),
+                value: json!(false),
+            },
+        ];
+
+        let error = apply_json_patch_value(&mut value, &operations).unwrap_err();
+
+        assert!(matches!(error, crate::PatchError::ApplyFailed(_)));
+        assert_eq!(value, json!({"enabled": true, "count": 1}));
+    }
+
+    #[test]
+    fn apply_json_patch_rejects_missing_remove_path() {
+        let error = apply_json_patch(r#"{"items":[]}"#, r#"[{"op":"remove","path":"/missing"}]"#)
+            .unwrap_err();
+
         assert!(matches!(error, crate::PatchError::ApplyFailed(_)));
     }
 }

crates/bat-patch/src/lib.rs

@@ -14,8 +14,14 @@
 pub mod binary;
 pub mod error;
 pub mod json;
+pub mod manifest;
+pub mod text;
 
 pub use error::{PatchError, Result};
+pub use manifest::{
+    PatchIntegrity, PatchKind, PatchManifest, PatchManifestFile, PatchRollback,
+    PATCH_MANIFEST_VERSION,
+};
 
 /// Patch 引擎版本号
 pub const VERSION: &str = env!("CARGO_PKG_VERSION");

crates/bat-patch/src/manifest.rs

@@ -0,0 +1,261 @@
+//! Patch manifest, integrity and rollback primitives.
+
+use crate::PatchError;
+use serde::{Deserialize, Serialize};
+use std::fs;
+use std::path::{Component, Path, PathBuf};
+
+/// Current patch manifest schema version.
+pub const PATCH_MANIFEST_VERSION: u32 = 1;
+
+/// Persisted manifest for a generated patch set.
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct PatchManifest {
+    /// Manifest schema version.
+    #[serde(default = "default_patch_manifest_version")]
+    pub version: u32,
+    /// Stable patch identifier.
+    pub patch_id: String,
+    /// Source resource version identifier.
+    pub source_version: String,
+    /// Target resource version identifier.
+    pub target_version: String,
+    /// Files covered by this patch set.
+    pub files: Vec<PatchManifestFile>,
+    /// Rollback metadata for the publication layer.
+    pub rollback: PatchRollback,
+}
+
+impl PatchManifest {
+    /// Builds a manifest-level integrity summary from recorded file metadata.
+    pub fn integrity_summary(&self) -> PatchIntegrity {
+        PatchIntegrity {
+            file_count: self.files.len(),
+            source_bytes: self.files.iter().map(|file| file.source_size).sum(),
+            target_bytes: self.files.iter().map(|file| file.target_size).sum(),
+        }
+    }
+}
+
+/// One release-relative file entry in a patch manifest.
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct PatchManifestFile {
+    /// Release-relative path.
+    pub path: PathBuf,
+    /// Patch algorithm used to produce the target bytes.
+    pub patch_kind: PatchKind,
+    /// Expected BLAKE3 hash of the source bytes.
+    pub source_blake3: String,
+    /// Expected BLAKE3 hash of the target bytes.
+    pub target_blake3: String,
+    /// Expected source byte length.
+    pub source_size: u64,
+    /// Expected target byte length.
+    pub target_size: u64,
+}
+
+/// Patch algorithm family used by one manifest file.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum PatchKind {
+    /// Deterministic binary hunk patch.
+    Binary,
+    /// RFC 6902 JSON Patch.
+    Json,
+    /// UTF-8 text patch.
+    Text,
+    /// UnityFS TextAsset replacement patch.
+    UnityFsTextAsset,
+}
+
+/// Rollback metadata owned by higher-level publication code.
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct PatchRollback {
+    /// Previous `current` pointer target before publication.
+    pub previous_current_target: Option<PathBuf>,
+    /// Published target path that can be removed on rollback.
+    pub remove_target_path: Option<PathBuf>,
+}
+
+/// Manifest-level integrity summary.
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct PatchIntegrity {
+    /// Number of manifest files verified or summarized.
+    pub file_count: usize,
+    /// Total source bytes.
+    pub source_bytes: u64,
+    /// Total target bytes.
+    pub target_bytes: u64,
+}
+
+/// Verifies all manifest files against source and target roots.
+pub fn verify_patch_manifest_files(
+    source_root: &Path,
+    target_root: &Path,
+    manifest: &PatchManifest,
+) -> crate::Result<PatchIntegrity> {
+    if manifest.version != PATCH_MANIFEST_VERSION {
+        return Err(PatchError::ApplyFailed(format!(
+            "unsupported patch manifest version {}",
+            manifest.version
+        )));
+    }
+
+    let mut integrity = PatchIntegrity {
+        file_count: 0,
+        source_bytes: 0,
+        target_bytes: 0,
+    };
+    for file in &manifest.files {
+        let source_path = resolve_manifest_path(source_root, &file.path)?;
+        let target_path = resolve_manifest_path(target_root, &file.path)?;
+        let source = read_manifest_file(&source_path, "source")?;
+        let target = read_manifest_file(&target_path, "target")?;
+        verify_patch_file_bytes(&source, &target, file)?;
+        integrity.file_count += 1;
+        integrity.source_bytes += source.len() as u64;
+        integrity.target_bytes += target.len() as u64;
+    }
+    Ok(integrity)
+}
+
+/// Verifies one manifest file entry against source and target bytes.
+pub fn verify_patch_file_bytes(
+    source: &[u8],
+    target: &[u8],
+    file: &PatchManifestFile,
+) -> crate::Result<()> {
+    let source_hash = blake3_hex(source);
+    let target_hash = blake3_hex(target);
+    if source_hash != file.source_blake3 || source.len() as u64 != file.source_size {
+        return Err(PatchError::ApplyFailed(format!(
+            "patch source integrity mismatch {}: expected hash={} bytes={}, actual hash={} bytes={}",
+            file.path.display(),
+            file.source_blake3,
+            file.source_size,
+            source_hash,
+            source.len()
+        )));
+    }
+    if target_hash != file.target_blake3 || target.len() as u64 != file.target_size {
+        return Err(PatchError::ApplyFailed(format!(
+            "patch target integrity mismatch {}: expected hash={} bytes={}, actual hash={} bytes={}",
+            file.path.display(),
+            file.target_blake3,
+            file.target_size,
+            target_hash,
+            target.len()
+        )));
+    }
+    Ok(())
+}
+
+fn resolve_manifest_path(root: &Path, relative: &Path) -> crate::Result<PathBuf> {
+    if relative.is_absolute() {
+        return Err(PatchError::ApplyFailed(format!(
+            "patch manifest path must be relative: {}",
+            relative.display()
+        )));
+    }
+    for component in relative.components() {
+        match component {
+            Component::Normal(_) | Component::CurDir => {}
+            _ => {
+                return Err(PatchError::ApplyFailed(format!(
+                    "patch manifest path escapes release root: {}",
+                    relative.display()
+                )))
+            }
+        }
+    }
+    Ok(root.join(relative))
+}
+
+fn read_manifest_file(path: &Path, label: &str) -> crate::Result<Vec<u8>> {
+    fs::read(path).map_err(|error| {
+        PatchError::ApplyFailed(format!(
+            "failed to read patch {label} file {}: {error}",
+            path.display()
+        ))
+    })
+}
+
+fn blake3_hex(bytes: &[u8]) -> String {
+    blake3::hash(bytes).to_hex().to_string()
+}
+
+fn default_patch_manifest_version() -> u32 {
+    PATCH_MANIFEST_VERSION
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn verify_patch_manifest_files_accepts_matching_roots() {
+        let temp = tempfile::tempdir().unwrap();
+        let source_root = temp.path().join("source");
+        let target_root = temp.path().join("target");
+        fs::create_dir_all(source_root.join("TableBundles")).unwrap();
+        fs::create_dir_all(target_root.join("TableBundles")).unwrap();
+        let source = b"before";
+        let target = b"after";
+        fs::write(source_root.join("TableBundles/file.bytes"), source).unwrap();
+        fs::write(target_root.join("TableBundles/file.bytes"), target).unwrap();
+
+        let manifest = manifest_for("TableBundles/file.bytes", source, target);
+        let integrity = verify_patch_manifest_files(&source_root, &target_root, &manifest).unwrap();
+
+        assert_eq!(
+            integrity,
+            PatchIntegrity {
+                file_count: 1,
+                source_bytes: source.len() as u64,
+                target_bytes: target.len() as u64,
+            }
+        );
+        assert_eq!(manifest.integrity_summary(), integrity);
+    }
+
+    #[test]
+    fn verify_patch_manifest_files_rejects_path_escape() {
+        let temp = tempfile::tempdir().unwrap();
+        let manifest = manifest_for("../escape", b"source", b"target");
+
+        let error = verify_patch_manifest_files(temp.path(), temp.path(), &manifest).unwrap_err();
+
+        assert!(matches!(error, PatchError::ApplyFailed(_)));
+    }
+
+    #[test]
+    fn verify_patch_file_bytes_rejects_hash_mismatch() {
+        let mut manifest = manifest_for("file.bin", b"source", b"target");
+        manifest.files[0].target_blake3 = blake3_hex(b"other");
+
+        let error = verify_patch_file_bytes(b"source", b"target", &manifest.files[0]).unwrap_err();
+
+        assert!(matches!(error, PatchError::ApplyFailed(_)));
+    }
+
+    fn manifest_for(path: &str, source: &[u8], target: &[u8]) -> PatchManifest {
+        PatchManifest {
+            version: PATCH_MANIFEST_VERSION,
+            patch_id: "patch-id".to_string(),
+            source_version: "source-version".to_string(),
+            target_version: "target-version".to_string(),
+            files: vec![PatchManifestFile {
+                path: PathBuf::from(path),
+                patch_kind: PatchKind::Binary,
+                source_blake3: blake3_hex(source),
+                target_blake3: blake3_hex(target),
+                source_size: source.len() as u64,
+                target_size: target.len() as u64,
+            }],
+            rollback: PatchRollback {
+                previous_current_target: None,
+                remove_target_path: None,
+            },
+        }
+    }
+}

crates/bat-patch/src/text.rs

@@ -0,0 +1,305 @@
+//! Deterministic UTF-8 text patch support.
+
+use crate::PatchError;
+use serde::{Deserialize, Serialize};
+
+/// Current text patch schema version.
+pub const TEXT_PATCH_VERSION: u32 = 1;
+
+/// UTF-8 text patch made of source-relative replacement ranges.
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct TextPatch {
+    /// Patch schema version.
+    pub version: u32,
+    /// Expected BLAKE3 hash of the source UTF-8 bytes.
+    pub source_blake3: String,
+    /// Expected BLAKE3 hash of the target UTF-8 bytes.
+    pub target_blake3: String,
+    /// Source byte length.
+    pub source_size: u64,
+    /// Target byte length.
+    pub target_size: u64,
+    /// Ordered source-relative operations.
+    pub operations: Vec<TextPatchOperation>,
+}
+
+/// One source-relative text patch operation.
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(tag = "kind", rename_all = "snake_case")]
+pub enum TextPatchOperation {
+    /// Replaces a UTF-8 byte range in the original source text.
+    ReplaceRange {
+        /// Byte offset in the original source text.
+        offset: u64,
+        /// Number of source bytes to replace.
+        length: u64,
+        /// Optional text that must exactly match the source range.
+        expected: Option<String>,
+        /// Replacement text.
+        replacement: String,
+    },
+}
+
+/// Builds a deterministic one-hunk text patch from source and target text.
+pub fn diff(source: &str, target: &str) -> TextPatch {
+    if source == target {
+        return TextPatch {
+            version: TEXT_PATCH_VERSION,
+            source_blake3: blake3_hex(source.as_bytes()),
+            target_blake3: blake3_hex(target.as_bytes()),
+            source_size: source.len() as u64,
+            target_size: target.len() as u64,
+            operations: Vec::new(),
+        };
+    }
+
+    let prefix = common_prefix_boundary(source, target);
+    let (source_suffix, target_suffix) = common_suffix_boundaries(source, target, prefix);
+    let operation = TextPatchOperation::ReplaceRange {
+        offset: prefix as u64,
+        length: (source_suffix - prefix) as u64,
+        expected: Some(source[prefix..source_suffix].to_string()),
+        replacement: target[prefix..target_suffix].to_string(),
+    };
+    TextPatch {
+        version: TEXT_PATCH_VERSION,
+        source_blake3: blake3_hex(source.as_bytes()),
+        target_blake3: blake3_hex(target.as_bytes()),
+        source_size: source.len() as u64,
+        target_size: target.len() as u64,
+        operations: vec![operation],
+    }
+}
+
+/// Builds a text patch from caller-provided source-relative operations.
+pub fn from_operations(
+    source: &str,
+    operations: Vec<TextPatchOperation>,
+) -> crate::Result<TextPatch> {
+    let target = apply_operations(source, &operations)?;
+    Ok(TextPatch {
+        version: TEXT_PATCH_VERSION,
+        source_blake3: blake3_hex(source.as_bytes()),
+        target_blake3: blake3_hex(target.as_bytes()),
+        source_size: source.len() as u64,
+        target_size: target.len() as u64,
+        operations,
+    })
+}
+
+/// Applies a structured text patch.
+pub fn apply_text_patch(source: &str, patch: &TextPatch) -> crate::Result<String> {
+    if patch.version != TEXT_PATCH_VERSION {
+        return Err(PatchError::ApplyFailed(format!(
+            "unsupported text patch version {}",
+            patch.version
+        )));
+    }
+    if patch.source_size != source.len() as u64
+        || patch.source_blake3 != blake3_hex(source.as_bytes())
+    {
+        return Err(PatchError::ApplyFailed(
+            "text patch source integrity mismatch".to_string(),
+        ));
+    }
+
+    let output = apply_operations(source, &patch.operations)?;
+    if output.len() as u64 != patch.target_size
+        || patch.target_blake3 != blake3_hex(output.as_bytes())
+    {
+        return Err(PatchError::ApplyFailed(
+            "text patch target integrity mismatch".to_string(),
+        ));
+    }
+    Ok(output)
+}
+
+/// Parses and applies a JSON-encoded text patch to a UTF-8 string.
+pub fn apply_patch(source: &str, patch: &str) -> crate::Result<String> {
+    let patch: TextPatch = serde_json::from_str(patch)
+        .map_err(|error| PatchError::ApplyFailed(format!("invalid text patch JSON: {error}")))?;
+    apply_text_patch(source, &patch)
+}
+
+/// Parses and applies a JSON-encoded text patch to UTF-8 bytes.
+pub fn apply_patch_bytes(source: &[u8], patch: &[u8]) -> crate::Result<Vec<u8>> {
+    let source = std::str::from_utf8(source)
+        .map_err(|error| PatchError::ApplyFailed(format!("source is not UTF-8: {error}")))?;
+    let patch = std::str::from_utf8(patch)
+        .map_err(|error| PatchError::ApplyFailed(format!("patch is not UTF-8: {error}")))?;
+    Ok(apply_patch(source, patch)?.into_bytes())
+}
+
+fn apply_operations(source: &str, operations: &[TextPatchOperation]) -> crate::Result<String> {
+    let mut output = String::with_capacity(source.len());
+    let mut cursor = 0usize;
+    for operation in operations {
+        let (offset, length, expected, replacement) = match operation {
+            TextPatchOperation::ReplaceRange {
+                offset,
+                length,
+                expected,
+                replacement,
+            } => (*offset, *length, expected, replacement),
+        };
+        let start = usize::try_from(offset)
+            .map_err(|_| PatchError::ApplyFailed("text patch offset overflow".to_string()))?;
+        let length = usize::try_from(length)
+            .map_err(|_| PatchError::ApplyFailed("text patch length overflow".to_string()))?;
+        if start < cursor {
+            return Err(PatchError::ApplyFailed(format!(
+                "text patch operation at {start} overlaps previous range ending at {cursor}"
+            )));
+        }
+        let end = start
+            .checked_add(length)
+            .ok_or_else(|| PatchError::ApplyFailed("text patch range overflow".to_string()))?;
+        let replaced = source.get(start..end).ok_or_else(|| {
+            PatchError::ApplyFailed(format!(
+                "text patch range {start}..{end} is outside the source or not UTF-8 aligned"
+            ))
+        })?;
+        if let Some(expected) = expected {
+            if replaced != expected {
+                return Err(PatchError::ApplyFailed(format!(
+                    "text patch expected mismatch at {start}..{end}"
+                )));
+            }
+        }
+        output.push_str(&source[cursor..start]);
+        output.push_str(replacement);
+        cursor = end;
+    }
+    output.push_str(&source[cursor..]);
+    Ok(output)
+}
+
+fn common_prefix_boundary(source: &str, target: &str) -> usize {
+    let mut prefix = 0usize;
+    for ((source_index, source_char), (target_index, target_char)) in
+        source.char_indices().zip(target.char_indices())
+    {
+        if source_index != target_index || source_char != target_char {
+            break;
+        }
+        prefix = source_index + source_char.len_utf8();
+    }
+    prefix
+}
+
+fn common_suffix_boundaries(source: &str, target: &str, prefix: usize) -> (usize, usize) {
+    let mut source_suffix = source.len();
+    let mut target_suffix = target.len();
+    let mut source_chars = source[prefix..].char_indices().rev();
+    let mut target_chars = target[prefix..].char_indices().rev();
+    while let (Some((source_index, source_char)), Some((target_index, target_char))) =
+        (source_chars.next(), target_chars.next())
+    {
+        if source_char != target_char {
+            break;
+        }
+        source_suffix = prefix + source_index;
+        target_suffix = prefix + target_index;
+    }
+    (source_suffix, target_suffix)
+}
+
+fn blake3_hex(bytes: &[u8]) -> String {
+    blake3::hash(bytes).to_hex().to_string()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn text_patch_round_trips_unicode_change() {
+        let source = "先生、こんにちは\nAbydos";
+        let target = "老师、你好\nAbydos";
+        let patch = diff(source, target);
+        let patch_json = serde_json::to_string(&patch).unwrap();
+
+        assert_eq!(apply_text_patch(source, &patch).unwrap(), target);
+        assert_eq!(apply_patch(source, &patch_json).unwrap(), target);
+        assert_eq!(
+            apply_patch_bytes(source.as_bytes(), patch_json.as_bytes()).unwrap(),
+            target.as_bytes()
+        );
+    }
+
+    #[test]
+    fn text_patch_applies_multiple_source_relative_ranges() {
+        let source = "alpha beta gamma";
+        let patch = from_operations(
+            source,
+            vec![
+                TextPatchOperation::ReplaceRange {
+                    offset: 0,
+                    length: 5,
+                    expected: Some("alpha".to_string()),
+                    replacement: "one".to_string(),
+                },
+                TextPatchOperation::ReplaceRange {
+                    offset: 11,
+                    length: 5,
+                    expected: Some("gamma".to_string()),
+                    replacement: "three".to_string(),
+                },
+            ],
+        )
+        .unwrap();
+
+        assert_eq!(apply_text_patch(source, &patch).unwrap(), "one beta three");
+    }
+
+    #[test]
+    fn text_patch_rejects_expected_mismatch() {
+        let source = "alpha beta";
+        let operation = TextPatchOperation::ReplaceRange {
+            offset: 0,
+            length: 5,
+            expected: Some("wrong".to_string()),
+            replacement: "one".to_string(),
+        };
+
+        let error = from_operations(source, vec![operation]).unwrap_err();
+
+        assert!(matches!(error, PatchError::ApplyFailed(_)));
+    }
+
+    #[test]
+    fn text_patch_rejects_overlapping_ranges() {
+        let source = "alpha beta";
+        let operation_a = TextPatchOperation::ReplaceRange {
+            offset: 0,
+            length: 5,
+            expected: None,
+            replacement: "one".to_string(),
+        };
+        let operation_b = TextPatchOperation::ReplaceRange {
+            offset: 3,
+            length: 2,
+            expected: None,
+            replacement: "two".to_string(),
+        };
+
+        let error = from_operations(source, vec![operation_a, operation_b]).unwrap_err();
+
+        assert!(matches!(error, PatchError::ApplyFailed(_)));
+    }
+
+    #[test]
+    fn text_patch_rejects_non_boundary_range() {
+        let source = "éclair";
+        let operation = TextPatchOperation::ReplaceRange {
+            offset: 1,
+            length: 1,
+            expected: None,
+            replacement: "e".to_string(),
+        };
+
+        let error = from_operations(source, vec![operation]).unwrap_err();
+
+        assert!(matches!(error, PatchError::ApplyFailed(_)));
+    }
+}