read_snapshot.py
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| 1 | """muse plumbing read-snapshot — emit full snapshot metadata as JSON. |
| 2 | |
| 3 | Reads a snapshot record by its SHA-256 ID and emits the complete JSON |
| 4 | representation including the file manifest. |
| 5 | |
| 6 | Output:: |
| 7 | |
| 8 | { |
| 9 | "snapshot_id": "<sha256>", |
| 10 | "created_at": "2026-03-18T12:00:00+00:00", |
| 11 | "file_count": 3, |
| 12 | "manifest": { |
| 13 | "tracks/drums.mid": "<sha256>", |
| 14 | "tracks/bass.mid": "<sha256>", |
| 15 | "tracks/piano.mid": "<sha256>" |
| 16 | } |
| 17 | } |
| 18 | |
| 19 | Plumbing contract |
| 20 | ----------------- |
| 21 | |
| 22 | - Exit 0: snapshot found and printed. |
| 23 | - Exit 1: snapshot not found or invalid snapshot ID format. |
| 24 | |
| 25 | Agent use |
| 26 | --------- |
| 27 | |
| 28 | Skip the manifest when you only need metadata:: |
| 29 | |
| 30 | muse plumbing read-snapshot <id> --no-manifest |
| 31 | # → {"snapshot_id": "...", "created_at": "...", "file_count": 3} |
| 32 | |
| 33 | Filter to a path prefix to avoid pulling the full manifest:: |
| 34 | |
| 35 | muse plumbing read-snapshot <id> --path-prefix src/ |
| 36 | """ |
| 37 | |
| 38 | from __future__ import annotations |
| 39 | |
| 40 | import argparse |
| 41 | import json |
| 42 | import logging |
| 43 | import sys |
| 44 | from typing import TypedDict |
| 45 | |
| 46 | from muse.core.errors import ExitCode |
| 47 | from muse.core.repo import require_repo |
| 48 | from muse.core.store import read_snapshot |
| 49 | from muse.core.validation import validate_object_id |
| 50 | from muse.core._types import Manifest |
| 51 | |
| 52 | logger = logging.getLogger(__name__) |
| 53 | |
| 54 | _FORMAT_CHOICES = ("json", "text") |
| 55 | |
| 56 | |
| 57 | class _SnapshotOutput(TypedDict, total=False): |
| 58 | snapshot_id: str |
| 59 | created_at: str |
| 60 | file_count: int |
| 61 | manifest: Manifest |
| 62 | |
| 63 | |
| 64 | def register(subparsers: "argparse._SubParsersAction[argparse.ArgumentParser]") -> None: |
| 65 | """Register the read-snapshot subcommand.""" |
| 66 | parser = subparsers.add_parser( |
| 67 | "read-snapshot", |
| 68 | help="Emit full snapshot metadata and manifest as JSON.", |
| 69 | description=__doc__, |
| 70 | formatter_class=argparse.RawDescriptionHelpFormatter, |
| 71 | ) |
| 72 | parser.add_argument( |
| 73 | "snapshot_id", |
| 74 | help="SHA-256 snapshot ID (64 hex chars).", |
| 75 | ) |
| 76 | parser.add_argument( |
| 77 | "--no-manifest", |
| 78 | action="store_true", |
| 79 | dest="no_manifest", |
| 80 | help=( |
| 81 | "Omit the file manifest from JSON output. " |
| 82 | "Returns only snapshot_id, created_at, and file_count — " |
| 83 | "ideal for agents doing metadata-only queries." |
| 84 | ), |
| 85 | ) |
| 86 | parser.add_argument( |
| 87 | "--path-prefix", "-p", |
| 88 | default=None, |
| 89 | dest="path_prefix", |
| 90 | metavar="PREFIX", |
| 91 | help="Filter manifest to paths starting with PREFIX.", |
| 92 | ) |
| 93 | parser.add_argument( |
| 94 | "--format", "-f", |
| 95 | dest="fmt", |
| 96 | default="json", |
| 97 | metavar="FORMAT", |
| 98 | help="Output format: json (default) or text.", |
| 99 | ) |
| 100 | parser.add_argument( |
| 101 | "--json", action="store_const", const="json", dest="fmt", |
| 102 | help="Shorthand for --format json.", |
| 103 | ) |
| 104 | parser.set_defaults(func=run) |
| 105 | |
| 106 | |
| 107 | def run(args: argparse.Namespace) -> None: |
| 108 | """Emit full snapshot metadata as JSON (default) or a compact text summary. |
| 109 | |
| 110 | A snapshot holds the complete file manifest (path → object_id mapping) |
| 111 | for a point in time. Every commit references exactly one snapshot. |
| 112 | Use ``muse plumbing ls-files --commit <id>`` if you want to look up a |
| 113 | snapshot from a commit ID rather than the snapshot ID directly. |
| 114 | |
| 115 | Use ``--no-manifest`` for lightweight metadata queries. |
| 116 | Use ``--path-prefix`` to scope the manifest to a subtree. |
| 117 | |
| 118 | Text format (``--format text``):: |
| 119 | |
| 120 | <snapshot_id[:12]> <file_count> files <created_at> |
| 121 | """ |
| 122 | fmt: str = args.fmt |
| 123 | snapshot_id: str = args.snapshot_id |
| 124 | no_manifest: bool = args.no_manifest |
| 125 | path_prefix: str | None = args.path_prefix |
| 126 | |
| 127 | if fmt not in _FORMAT_CHOICES: |
| 128 | print( |
| 129 | json.dumps({"error": f"Unknown format {fmt!r}. Valid: {', '.join(_FORMAT_CHOICES)}"}), |
| 130 | file=sys.stderr, |
| 131 | ) |
| 132 | raise SystemExit(ExitCode.USER_ERROR) |
| 133 | |
| 134 | if no_manifest and fmt == "text": |
| 135 | print( |
| 136 | json.dumps({"error": "--no-manifest is only valid with --format json"}), |
| 137 | file=sys.stderr, |
| 138 | ) |
| 139 | raise SystemExit(ExitCode.USER_ERROR) |
| 140 | |
| 141 | if path_prefix is not None and fmt == "text": |
| 142 | print( |
| 143 | json.dumps({"error": "--path-prefix is only valid with --format json"}), |
| 144 | file=sys.stderr, |
| 145 | ) |
| 146 | raise SystemExit(ExitCode.USER_ERROR) |
| 147 | |
| 148 | try: |
| 149 | validate_object_id(snapshot_id) |
| 150 | except ValueError as exc: |
| 151 | print(json.dumps({"error": f"Invalid snapshot ID: {exc}"}), file=sys.stderr) |
| 152 | raise SystemExit(ExitCode.USER_ERROR) |
| 153 | |
| 154 | root = require_repo() |
| 155 | |
| 156 | record = read_snapshot(root, snapshot_id) |
| 157 | if record is None: |
| 158 | print(json.dumps({"error": f"Snapshot not found: {snapshot_id}"}), file=sys.stderr) |
| 159 | raise SystemExit(ExitCode.USER_ERROR) |
| 160 | |
| 161 | if fmt == "text": |
| 162 | print( |
| 163 | f"{record.snapshot_id[:12]} {len(record.manifest)} files " |
| 164 | f"{record.created_at.isoformat()}" |
| 165 | ) |
| 166 | return |
| 167 | |
| 168 | manifest = record.manifest |
| 169 | if path_prefix is not None: |
| 170 | manifest = {p: oid for p, oid in manifest.items() if p.startswith(path_prefix)} |
| 171 | |
| 172 | output: _SnapshotOutput = { |
| 173 | "snapshot_id": record.snapshot_id, |
| 174 | "created_at": record.created_at.isoformat(), |
| 175 | "file_count": len(manifest), |
| 176 | } |
| 177 | if not no_manifest: |
| 178 | output["manifest"] = manifest |
| 179 | |
| 180 | print(json.dumps(output, indent=2)) |