|
| 1 | +package types |
| 2 | + |
| 3 | +import ( |
| 4 | + "encoding/json" |
| 5 | + "fmt" |
| 6 | + |
| 7 | + "golang.org/x/xerrors" |
| 8 | + |
| 9 | + "github.com/filecoin-project/go-jsonrpc" |
| 10 | + "github.com/filecoin-project/go-state-types/abi" |
| 11 | +) |
| 12 | + |
| 13 | +// TipSetTag is a string that represents a pointer to a tipset. |
| 14 | +// See TipSetCriterion. |
| 15 | +type TipSetTag string |
| 16 | + |
| 17 | +// TipSetTags represents the predefined set of tags for tipsets. The supported |
| 18 | +// tags are: |
| 19 | +// - Latest: the most recent tipset in the chain with the heaviest weight. |
| 20 | +// - Finalized: the most recent tipset considered final by the node. |
| 21 | +// |
| 22 | +// See TipSetTag. |
| 23 | +var TipSetTags = struct { |
| 24 | + Latest TipSetTag |
| 25 | + Finalized TipSetTag |
| 26 | +}{ |
| 27 | + Latest: TipSetTag("latest"), |
| 28 | + Finalized: TipSetTag("finalized"), |
| 29 | +} |
| 30 | + |
| 31 | +// TipSetSelector is a JSON-RPC parameter type that can be used to select a tipset. |
| 32 | +// See NewTipSetSelector, TipSetCriterion. |
| 33 | +type TipSetSelector = jsonrpc.RawParams |
| 34 | + |
| 35 | +// TipSetCriterion captures the selection criteria for a tipset. |
| 36 | +// |
| 37 | +// The supported criterion for selection is one of the following: |
| 38 | +// - Key: the tipset key, see TipSetKey. |
| 39 | +// - Height: the tipset height with an optional fallback to non-null parent, see TipSetHeight. |
| 40 | +// - Tag: the tipset tag, either "latest" or "finalized", see TipSetTags. |
| 41 | +// |
| 42 | +// At most, only one such criterion can be specified at a time. Otherwise, the |
| 43 | +// criterion is considered. See Validate. |
| 44 | +type TipSetCriterion struct { |
| 45 | + Key *TipSetKey `json:"key,omitempty"` |
| 46 | + Height *TipSetHeight `json:"height,omitempty"` |
| 47 | + Tag *TipSetTag `json:"tag,omitempty"` |
| 48 | +} |
| 49 | + |
| 50 | +// TipSetCriteria is a union of all possible criteria for selecting a tipset. |
| 51 | +type TipSetCriteria interface { |
| 52 | + TipSetTag | TipSetHeight | TipSetKey |
| 53 | +} |
| 54 | + |
| 55 | +// NewTipSetSelector creates a new TipSetSelector from the given criterion. The |
| 56 | +// criterion must conform to one of the supported types: TipSetTag, TipSetHeight, |
| 57 | +// or TipSetKey. |
| 58 | +// |
| 59 | +// See TipSetCriteria type constraint. |
| 60 | +func NewTipSetSelector[T TipSetCriteria](t T) (TipSetSelector, error) { |
| 61 | + switch criterion := any(t).(type) { |
| 62 | + case TipSetTag: |
| 63 | + return json.Marshal(TipSetCriterion{Tag: &criterion}) |
| 64 | + case TipSetHeight: |
| 65 | + return json.Marshal(TipSetCriterion{Height: &criterion}) |
| 66 | + case TipSetKey: |
| 67 | + return json.Marshal(TipSetCriterion{Key: &criterion}) |
| 68 | + default: |
| 69 | + // Dear Golang, this should be impossible because of the type constraint being |
| 70 | + // evaluated at compile time; yet, here we are. I would panic, but then we are |
| 71 | + // friends and this function returns errors anyhow. |
| 72 | + return nil, fmt.Errorf("unknown tipset slection criterion: %T", criterion) |
| 73 | + } |
| 74 | +} |
| 75 | + |
| 76 | +// DecodeTipSetCriterion extracts a TipSetCriterion from the given |
| 77 | +// TipSetSelector. The returned criterion is validated before returning. If the |
| 78 | +// selector is empty, a nil criterion is returned. |
| 79 | +func DecodeTipSetCriterion(tss TipSetSelector) (*TipSetCriterion, error) { |
| 80 | + if len(tss) == 0 || string(tss) == "null" { |
| 81 | + return nil, nil |
| 82 | + } |
| 83 | + |
| 84 | + var criterion TipSetCriterion |
| 85 | + if err := json.Unmarshal(tss, &criterion); err != nil { |
| 86 | + return nil, xerrors.Errorf("decoding tipset selector: %w", err) |
| 87 | + } |
| 88 | + if err := criterion.Validate(); err != nil { |
| 89 | + return nil, xerrors.Errorf("validating tipset criterion: %w", err) |
| 90 | + } |
| 91 | + return &criterion, nil |
| 92 | +} |
| 93 | + |
| 94 | +// Validate ensures that the TipSetCriterion is valid. It checks that only one of |
| 95 | +// the selection criteria is specified. If no criteria are specified, it returns |
| 96 | +// nil, indicating that the default selection criteria should be used as defined |
| 97 | +// by the Lotus API Specification. |
| 98 | +func (tss *TipSetCriterion) Validate() error { |
| 99 | + if tss == nil { |
| 100 | + // Empty TipSetSelector is valid and implies whatever the default is dictated to |
| 101 | + // be by the API, which happens to be the tipset tagged as "latest". |
| 102 | + return nil |
| 103 | + } |
| 104 | + var criteria int |
| 105 | + if tss.Key != nil { |
| 106 | + criteria++ |
| 107 | + } |
| 108 | + if tss.Tag != nil { |
| 109 | + criteria++ |
| 110 | + } |
| 111 | + if tss.Height != nil { |
| 112 | + criteria++ |
| 113 | + } |
| 114 | + if criteria > 1 { |
| 115 | + return xerrors.Errorf("only one tipset selection criteria must be specified, found: %v", criteria) |
| 116 | + } |
| 117 | + return nil |
| 118 | +} |
| 119 | + |
| 120 | +// TipSetHeight is a criterion that selects a tipset At given height. |
| 121 | +// |
| 122 | +// In a case where the tipset at given height is null, and Previous is true, |
| 123 | +// it'll select the previous non-null tipset instead. Otherwise, it returns the |
| 124 | +// null tipset at the given height. |
| 125 | +type TipSetHeight struct { |
| 126 | + At abi.ChainEpoch `json:"at,omitempty"` |
| 127 | + Previous bool `json:"previous,omitempty"` |
| 128 | +} |
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