| 1 | package sync |
| 2 | |
| 3 | import ( |
| 4 | "os" |
| 5 | "path" |
| 6 | "path/filepath" |
| 7 | "sort" |
| 8 | "strings" |
| 9 | |
| 10 | "go.bigb.es/auxilia/culpa" |
| 11 | "go.bigb.es/auxilia/legatus" |
| 12 | ) |
| 13 | |
| 14 | // Diff is a read-only step: it downloads each remote file, compares it to its |
| 15 | // local counterpart, and reports a unified diff. It never writes anywhere — |
| 16 | // Outcome.Changed is always false (PC: idempotent, observation-only). The |
| 17 | // rendered diff is in Outcome.Data (string); empty string means no differences. |
| 18 | type Diff struct { |
| 19 | // Files are individual paths relative to LocalRoot/RemoteRoot. |
| 20 | Files []string |
| 21 | // Dirs are directory paths (relative) compared recursively. |
| 22 | Dirs []string |
| 23 | // LocalRoot is the base of the local tree. |
| 24 | LocalRoot string |
| 25 | // RemoteRoot is the base of the remote tree. |
| 26 | RemoteRoot string |
| 27 | // Normalize, when set, is applied to both local and remote bytes before the |
| 28 | // equality test, so a JSON-canonicalizer or whitespace-normalizer makes the |
| 29 | // comparison semantic. The rendered diff is of the normalized forms. |
| 30 | Normalize func([]byte) ([]byte, error) |
| 31 | // Summary, when set, makes Apply report a content-free per-file verdict |
| 32 | // ("rel: same" / "rel: differs") instead of a unified diff — so secret-bearing |
| 33 | // files can be diffed for change-detection without printing their content. |
| 34 | Summary bool |
| 35 | } |
| 36 | |
| 37 | // Name identifies the step. |
| 38 | func (d *Diff) Name() string { return "sync.diff" } |
| 39 | |
| 40 | // fileStatus is one file's comparison result. diff holds the rendered unified |
| 41 | // diff (empty in Summary mode or when the file matches). |
| 42 | type fileStatus struct { |
| 43 | rel string |
| 44 | differs bool |
| 45 | diff string |
| 46 | } |
| 47 | |
| 48 | // Check reports whether any file differs. |
| 49 | func (d *Diff) Check(fc *legatus.FlowCtx) (bool, error) { |
| 50 | sts, err := d.statuses(fc) |
| 51 | if err != nil { |
| 52 | return false, err |
| 53 | } |
| 54 | for _, s := range sts { |
| 55 | if s.differs { |
| 56 | return true, nil |
| 57 | } |
| 58 | } |
| 59 | return false, nil |
| 60 | } |
| 61 | |
| 62 | // Apply renders the comparison and reports it. It is read-only: Changed is false. |
| 63 | // In Summary mode the Data is a content-free per-file verdict; otherwise it is |
| 64 | // the concatenated unified diffs of the differing files. |
| 65 | func (d *Diff) Apply(fc *legatus.FlowCtx) (legatus.Outcome, error) { |
| 66 | sts, err := d.statuses(fc) |
| 67 | if err != nil { |
| 68 | return legatus.Outcome{}, err |
| 69 | } |
| 70 | var b strings.Builder |
| 71 | any := false |
| 72 | for _, s := range sts { |
| 73 | if s.differs { |
| 74 | any = true |
| 75 | } |
| 76 | switch { |
| 77 | case d.Summary: |
| 78 | verdict := "same" |
| 79 | if s.differs { |
| 80 | verdict = "differs" |
| 81 | } |
| 82 | b.WriteString(s.rel + ": " + verdict + "\n") |
| 83 | case s.differs: |
| 84 | b.WriteString(s.diff) |
| 85 | } |
| 86 | } |
| 87 | msg := "no differences" |
| 88 | if any { |
| 89 | msg = "differences found" |
| 90 | } |
| 91 | return legatus.Outcome{Changed: false, Message: msg, Data: b.String()}, nil |
| 92 | } |
| 93 | |
| 94 | func (d *Diff) statuses(fc *legatus.FlowCtx) ([]fileStatus, error) { |
| 95 | rels, err := d.relPaths() |
| 96 | if err != nil { |
| 97 | return nil, err |
| 98 | } |
| 99 | out := make([]fileStatus, 0, len(rels)) |
| 100 | for _, rel := range rels { |
| 101 | localPath := filepath.Join(d.LocalRoot, filepath.FromSlash(rel)) |
| 102 | remotePath := path.Join(d.RemoteRoot, rel) |
| 103 | |
| 104 | localData, lerr := os.ReadFile(localPath) |
| 105 | localMissing := os.IsNotExist(lerr) |
| 106 | if lerr != nil && !localMissing { |
| 107 | return nil, culpa.Wrapf(lerr, "sync: read local %s", localPath) |
| 108 | } |
| 109 | |
| 110 | remoteData, err := downloadRemote(fc.Ctx(), fc.Conn(), remotePath) |
| 111 | if err != nil { |
| 112 | return nil, err |
| 113 | } |
| 114 | |
| 115 | local, remote := localData, remoteData |
| 116 | if d.Normalize != nil { |
| 117 | if local, err = d.Normalize(localData); err != nil { |
| 118 | return nil, culpa.Wrapf(err, "sync: normalize local %s", rel) |
| 119 | } |
| 120 | if remote, err = d.Normalize(remoteData); err != nil { |
| 121 | return nil, culpa.Wrapf(err, "sync: normalize remote %s", rel) |
| 122 | } |
| 123 | } |
| 124 | |
| 125 | st := fileStatus{rel: rel, differs: string(local) != string(remote)} |
| 126 | if st.differs && !d.Summary { |
| 127 | st.diff = unifiedDiff(rel, remote, local) |
| 128 | } |
| 129 | out = append(out, st) |
| 130 | } |
| 131 | return out, nil |
| 132 | } |
| 133 | |
| 134 | func (d *Diff) relPaths() ([]string, error) { |
| 135 | set := map[string]bool{} |
| 136 | for _, f := range d.Files { |
| 137 | set[filepath.ToSlash(f)] = true |
| 138 | } |
| 139 | for _, dir := range d.Dirs { |
| 140 | locals, err := walkLocalDir(d.LocalRoot, dir) |
| 141 | if err != nil { |
| 142 | return nil, err |
| 143 | } |
| 144 | for rel := range locals { |
| 145 | set[rel] = true |
| 146 | } |
| 147 | } |
| 148 | rels := make([]string, 0, len(set)) |
| 149 | for rel := range set { |
| 150 | rels = append(rels, rel) |
| 151 | } |
| 152 | sort.Strings(rels) |
| 153 | return rels, nil |
| 154 | } |
| 155 | |
| 156 | // unifiedDiff renders a minimal unified diff between remote (a) and local (b) |
| 157 | // content for display. It emits a full-context block; this is a human-facing |
| 158 | // report, not a machine patch. |
| 159 | func unifiedDiff(name string, a, b []byte) string { |
| 160 | aLines := splitKeepLines(string(a)) |
| 161 | bLines := splitKeepLines(string(b)) |
| 162 | |
| 163 | var sb strings.Builder |
| 164 | sb.WriteString("--- remote/" + name + "\n") |
| 165 | sb.WriteString("+++ local/" + name + "\n") |
| 166 | |
| 167 | la, lb := lcs(aLines, bLines) |
| 168 | ia, ib := 0, 0 |
| 169 | for _, op := range diffOps(aLines, bLines, la, lb) { |
| 170 | switch op.kind { |
| 171 | case opEqual: |
| 172 | sb.WriteString(" " + aLines[ia]) |
| 173 | ia++ |
| 174 | ib++ |
| 175 | case opDel: |
| 176 | sb.WriteString("-" + aLines[ia]) |
| 177 | ia++ |
| 178 | case opAdd: |
| 179 | sb.WriteString("+" + bLines[ib]) |
| 180 | ib++ |
| 181 | } |
| 182 | } |
| 183 | if !strings.HasSuffix(sb.String(), "\n") { |
| 184 | sb.WriteString("\n") |
| 185 | } |
| 186 | return sb.String() |
| 187 | } |
| 188 | |
| 189 | func splitKeepLines(s string) []string { |
| 190 | if s == "" { |
| 191 | return nil |
| 192 | } |
| 193 | parts := strings.SplitAfter(s, "\n") |
| 194 | if parts[len(parts)-1] == "" { |
| 195 | parts = parts[:len(parts)-1] |
| 196 | } |
| 197 | return parts |
| 198 | } |
| 199 | |
| 200 | type diffKind int |
| 201 | |
| 202 | const ( |
| 203 | opEqual diffKind = iota |
| 204 | opDel |
| 205 | opAdd |
| 206 | ) |
| 207 | |
| 208 | type diffOp struct{ kind diffKind } |
| 209 | |
| 210 | // lcs builds the length table for the longest common subsequence of a and b. |
| 211 | func lcs(a, b []string) ([][]int, int) { |
| 212 | n, m := len(a), len(b) |
| 213 | t := make([][]int, n+1) |
| 214 | for i := range t { |
| 215 | t[i] = make([]int, m+1) |
| 216 | } |
| 217 | for i := n - 1; i >= 0; i-- { |
| 218 | for j := m - 1; j >= 0; j-- { |
| 219 | if a[i] == b[j] { |
| 220 | t[i][j] = t[i+1][j+1] + 1 |
| 221 | } else if t[i+1][j] >= t[i][j+1] { |
| 222 | t[i][j] = t[i+1][j] |
| 223 | } else { |
| 224 | t[i][j] = t[i][j+1] |
| 225 | } |
| 226 | } |
| 227 | } |
| 228 | return t, t[0][0] |
| 229 | } |
| 230 | |
| 231 | // diffOps walks the LCS table to produce an ordered edit script. |
| 232 | func diffOps(a, b []string, t [][]int, _ int) []diffOp { |
| 233 | var ops []diffOp |
| 234 | i, j := 0, 0 |
| 235 | n, m := len(a), len(b) |
| 236 | for i < n && j < m { |
| 237 | if a[i] == b[j] { |
| 238 | ops = append(ops, diffOp{opEqual}) |
| 239 | i++ |
| 240 | j++ |
| 241 | } else if t[i+1][j] >= t[i][j+1] { |
| 242 | ops = append(ops, diffOp{opDel}) |
| 243 | i++ |
| 244 | } else { |
| 245 | ops = append(ops, diffOp{opAdd}) |
| 246 | j++ |
| 247 | } |
| 248 | } |
| 249 | for ; i < n; i++ { |
| 250 | ops = append(ops, diffOp{opDel}) |
| 251 | } |
| 252 | for ; j < m; j++ { |
| 253 | ops = append(ops, diffOp{opAdd}) |
| 254 | } |
| 255 | return ops |
| 256 | } |
| 257 | |