agent-migrate-core 0.6.1

Core models and transactional filesystem engine for agent configuration migration
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133

use std::path::PathBuf;

use serde::{Deserialize, Serialize};
use sha2::{Digest, Sha256};

use crate::BundleRelativePath;
use crate::transaction::filesystem::FileSystem;
use crate::transaction::{SnapshotId, TransactionError, TransactionOptions, WritePlan};

#[derive(Debug)]
pub(crate) struct SnapshotStore<'a> {
    filesystem: FileSystem,
    options: &'a TransactionOptions,
}

impl<'a> SnapshotStore<'a> {
    pub(crate) const fn new(filesystem: FileSystem, options: &'a TransactionOptions) -> Self {
        Self {
            filesystem,
            options,
        }
    }

    pub(crate) fn create(
        &self,
        snapshot_id: SnapshotId,
        plan: &WritePlan,
    ) -> Result<(), TransactionError> {
        let directory = self.directory(snapshot_id);
        let files_root = directory.join("files");
        FileSystem::create_private_dir(&directory)?;
        FileSystem::create_private_dir(&files_root)?;
        let mut entries = Vec::with_capacity(plan.len());
        for write in plan.writes() {
            let target = self.options.root().join(write.path.as_path());
            let existed = target.is_file();
            let (mode, sha256) = if existed {
                let backup = files_root.join(write.path.as_path());
                if let Some(parent) = backup.parent() {
                    FileSystem::create_private_dir(parent)?;
                }
                FileSystem::copy(&target, &backup)?;
                let content = FileSystem::read(&backup)?;
                (
                    file_mode(&target)?,
                    Some(hex::encode(Sha256::digest(content))),
                )
            } else {
                (None, None)
            };
            entries.push(SnapshotEntry {
                path: write.path.clone(),
                existed,
                mode,
                sha256,
            });
        }
        let manifest = serde_json::to_vec_pretty(&SnapshotManifest { entries })
            .map_err(TransactionError::InvalidSnapshot)?;
        FileSystem::write(&directory.join("manifest.json"), &manifest)
    }

    pub(crate) fn restore(&self, snapshot_id: SnapshotId) -> Result<(), TransactionError> {
        let directory = self.directory(snapshot_id);
        let manifest_path = directory.join("manifest.json");
        if !manifest_path.is_file() {
            return Err(TransactionError::SnapshotNotFound(snapshot_id));
        }
        let manifest_bytes = FileSystem::read(&manifest_path)?;
        let manifest: SnapshotManifest =
            serde_json::from_slice(&manifest_bytes).map_err(TransactionError::InvalidSnapshot)?;
        for entry in manifest.entries {
            FileSystem::ensure_path_safe(self.options.root(), entry.path.as_path())?;
            let target = self.options.root().join(entry.path.as_path());
            if entry.existed {
                let backup = directory.join("files").join(entry.path.as_path());
                let content = FileSystem::read(&backup)?;
                if entry.sha256.as_deref() != Some(&hex::encode(Sha256::digest(&content))) {
                    return Err(TransactionError::SnapshotHashMismatch { path: backup });
                }
                self.filesystem.atomic_write(
                    self.options.root(),
                    &target,
                    &content,
                    entry.mode.unwrap_or(0o600),
                )?;
            } else if target.is_file() {
                FileSystem::remove_file(&target)?;
                if let Some(parent) = target.parent() {
                    FileSystem::remove_empty_parents(self.options.root(), parent)?;
                }
            }
        }
        Ok(())
    }

    fn directory(&self, snapshot_id: SnapshotId) -> PathBuf {
        self.options
            .state_root()
            .join("backups")
            .join(snapshot_id.to_string())
    }
}

#[derive(Debug, Serialize, Deserialize)]
struct SnapshotManifest {
    entries: Vec<SnapshotEntry>,
}

#[derive(Debug, Serialize, Deserialize)]
struct SnapshotEntry {
    path: BundleRelativePath,
    existed: bool,
    mode: Option<u32>,
    sha256: Option<String>,
}

#[cfg(unix)]
fn file_mode(path: &std::path::Path) -> Result<Option<u32>, TransactionError> {
    use std::os::unix::fs::PermissionsExt;

    std::fs::metadata(path)
        .map(|metadata| Some(metadata.permissions().mode() & 0o777))
        .map_err(|source| TransactionError::Io {
            path: path.to_path_buf(),
            source,
        })
}

#[cfg(not(unix))]
fn file_mode(_path: &std::path::Path) -> Result<Option<u32>, TransactionError> {
    Ok(None)
}