| 1 | package hostclaim |
| 2 | |
| 3 | import ( |
| 4 | "bytes" |
| 5 | "context" |
| 6 | "encoding/json" |
| 7 | "errors" |
| 8 | "fmt" |
| 9 | "io" |
| 10 | "math" |
| 11 | "os" |
| 12 | |
| 13 | "github.com/carlosframework/platform/internal/release" |
| 14 | ) |
| 15 | |
| 16 | var ErrConflict = fmt.Errorf("hostclaim: claim changed since it was read: %w", release.ErrCASConflict) |
| 17 | |
| 18 | type Observed struct { |
| 19 | Host string |
| 20 | Claim *Claim |
| 21 | ETag string |
| 22 | Absent bool |
| 23 | } |
| 24 | |
| 25 | func decodeStrict(body []byte) (*Claim, error) { |
| 26 | dec := json.NewDecoder(bytes.NewReader(body)) |
| 27 | dec.DisallowUnknownFields() |
| 28 | var c Claim |
| 29 | if err := dec.Decode(&c); err != nil { |
| 30 | return nil, fmt.Errorf("%w: %v", ErrMalformed, err) |
| 31 | } |
| 32 | if _, err := dec.Token(); err != io.EOF { |
| 33 | return nil, fmt.Errorf("%w: trailing data", ErrMalformed) |
| 34 | } |
| 35 | return &c, nil |
| 36 | } |
| 37 | |
| 38 | func Read(ctx context.Context, s release.Store, host string) (Observed, error) { |
| 39 | key, err := Key(host) |
| 40 | if err != nil { |
| 41 | return Observed{}, err |
| 42 | } |
| 43 | body, etag, err := s.Get(ctx, key) |
| 44 | if errors.Is(err, os.ErrNotExist) { |
| 45 | return Observed{Host: host, Absent: true}, nil |
| 46 | } |
| 47 | if err != nil { |
| 48 | return Observed{}, err // C6: an error is never absence |
| 49 | } |
| 50 | c, err := decodeStrict(body) |
| 51 | if err != nil { |
| 52 | return Observed{}, err |
| 53 | } |
| 54 | if c.Host != host { |
| 55 | return Observed{}, fmt.Errorf("%w: host mismatch", ErrMalformed) |
| 56 | } |
| 57 | if err := c.Validate(); err != nil { |
| 58 | return Observed{}, err |
| 59 | } |
| 60 | return Observed{Host: host, Claim: c, ETag: etag}, nil |
| 61 | } |
| 62 | |
| 63 | func Update(ctx context.Context, s release.Store, obs Observed, tr func(*Claim) error) (Observed, error) { |
| 64 | key, err := Key(obs.Host) |
| 65 | if err != nil { |
| 66 | return Observed{}, err |
| 67 | } |
| 68 | var next *Claim |
| 69 | var oldGen uint64 |
| 70 | if obs.Absent { |
| 71 | next = &Claim{V: schemaVersion, Host: obs.Host} |
| 72 | } else { |
| 73 | if obs.ETag == "" { |
| 74 | return Observed{}, fmt.Errorf("%w: non-absent observation without ETag", ErrMalformed) |
| 75 | } |
| 76 | if obs.Claim == nil || obs.Claim.Host != obs.Host { |
| 77 | return Observed{}, fmt.Errorf("%w: observation not bound to %s", ErrMalformed, obs.Host) |
| 78 | } |
| 79 | raw, err := json.Marshal(obs.Claim) |
| 80 | if err != nil { |
| 81 | return Observed{}, err |
| 82 | } |
| 83 | if next, err = decodeStrict(raw); err != nil { |
| 84 | return Observed{}, err |
| 85 | } |
| 86 | oldGen = obs.Claim.Gen |
| 87 | if obs.Claim.Origins != nil || originEnabled() { |
| 88 | fresh, err := Read(ctx, s, obs.Host) |
| 89 | if err != nil { |
| 90 | return Observed{}, err |
| 91 | } |
| 92 | if fresh.Absent || fresh.ETag != obs.ETag || !sameOriginHead(fresh.Claim.Origins, obs.Claim.Origins) { |
| 93 | return Observed{}, ErrConflict |
| 94 | } |
| 95 | } |
| 96 | } |
| 97 | if err := tr(next); err != nil { |
| 98 | return Observed{}, err |
| 99 | } |
| 100 | if next.Host != obs.Host || next.Gen != oldGen { |
| 101 | return Observed{}, fmt.Errorf("%w: a transition may not change host or gen", ErrMalformed) |
| 102 | } |
| 103 | if oldGen == math.MaxUint64 { |
| 104 | return Observed{}, fmt.Errorf("%w: gen overflow", ErrMalformed) |
| 105 | } |
| 106 | next.Gen = oldGen + 1 |
| 107 | if err := next.Validate(); err != nil { |
| 108 | return Observed{}, err |
| 109 | } |
| 110 | if err := commitOrigins(ctx, s, obs, next); err != nil { |
| 111 | return Observed{}, err |
| 112 | } |
| 113 | body, err := json.Marshal(next) |
| 114 | if err != nil { |
| 115 | return Observed{}, err |
| 116 | } |
| 117 | ifMatch := obs.ETag |
| 118 | if obs.Absent { |
| 119 | ifMatch = "" // the host's very first claim (C5a) |
| 120 | } |
| 121 | etag, err := s.Put(ctx, key, body, ifMatch) |
| 122 | if errors.Is(err, release.ErrCASConflict) { |
| 123 | return Observed{}, ErrConflict |
| 124 | } |
| 125 | if err != nil { |
| 126 | return Observed{}, err |
| 127 | } |
| 128 | return Observed{Host: obs.Host, Claim: next, ETag: etag}, nil |
| 129 | } |
| 130 | |
amadan