feat: indexer base types

indexer/base/CHANGELOG.md

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+<!--
+Guiding Principles:
+
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+The same types of changes should be grouped.
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+Types of changes (Stanzas):
+
+"Features" for new features.
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+Ref: https://keepachangelog.com/en/1.0.0/
+-->
+
+# Changelog
+
+## [Unreleased]

indexer/base/README.md

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+# Indexer Base
+
+The indexer base module is designed to provide a stable, zero-dependency base layer for the built-in indexer functionality. Packages that integrate with the indexer should feel free to depend on this package without fear of any external dependencies being pulled in.
+
+The basic types for specifying index sources, targets and decoders are provided here. An indexing source should accept a `Listener` instance and invoke the provided callbacks in the correct order. An indexer should provide a `Listener` instance and perform indexing operations based on the data passed to its callbacks. A module that exposes logical updates in the form of `ObjectUpdate`s should implement the `IndexableModule` interface.
+
+## `Listener` Callback Order
+
+`Listener` callbacks should be called in this order
+
+```mermaid
+sequenceDiagram
+    actor Source
+    participant Indexer    
+    Source ->> Indexer: Initialize
+    Source -->> Indexer: InitializeModuleSchema
+    loop Block
+        Source ->> Indexer: StartBlock
+        Source ->> Indexer: OnBlockHeader
+        Source -->> Indexer: OnTx
+        Source -->> Indexer: OnEvent
+        Source -->> Indexer: OnKVPair
+        Source -->> Indexer: OnObjectUpdate
+        Source ->> Indexer: Commit
+    end
+```
+
+`Initialize` must be called before any other method and should only be invoked once. `InitializeModuleSchema` should be called at most once for every module with logical data.
+
+Sources will generally only call `InitializeModuleSchema` and `OnObjectUpdate` if they have native logical decoding capabilities. Usually, the indexer framework will provide this functionality based on `OnKVPair` data and `IndexableModule` implementations.
+
+`StartBlock` and `OnBlockHeader` should be called only once at the beginning of a block, and `Commit` should be called only once at the end of a block. The `OnTx`, `OnEvent`, `OnKVPair` and `OnObjectUpdate` must be called after `OnBlockHeader`, may be called multiple times within a block and indexers should not assume that the order is logical unless `InitializationData.HasEventAlignedWrites` is true. 

indexer/base/decoder.go

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+package indexerbase
+
+// DecodableModule is an interface that modules can implement to provide a ModuleDecoder.
+// Usually these modules would also implement appmodule.AppModule, but that is not included
+// to keep this package free of any dependencies.
+type DecodableModule interface {
+	// ModuleDecoder returns a ModuleDecoder for the module.
+	ModuleDecoder() (ModuleDecoder, error)
+}
+
+// ModuleDecoder is a struct that contains the schema and a KVDecoder for a module.
+type ModuleDecoder struct {
+	// Schema is the schema for the module.
+	Schema ModuleSchema
+
+	// KVDecoder is a function that decodes a key-value pair into an ObjectUpdate.
+	// If modules pass logical updates directly to the engine and don't require logical decoding of raw bytes,
+	// then this function should be nil.
+	KVDecoder KVDecoder
+}
+
+// KVDecoder is a function that decodes a key-value pair into an ObjectUpdate.
+// If the KV-pair doesn't represent an object update, the function should return false
+// as the second return value. Error should only be non-nil when the decoder expected
+// to parse a valid update and was unable to.
+type KVDecoder = func(key, value []byte) (ObjectUpdate, bool, error)

indexer/base/enum.go

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+package indexerbase
+
+// EnumDefinition represents the definition of an enum type.
+type EnumDefinition struct {
+	// Name is the name of the enum type.
+	Name string
+
+	// Values is a list of distinct values that are part of the enum type.
+	Values []string
+}

indexer/base/field.go

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+package indexerbase
+
+// Field represents a field in an object type.
+type Field struct {
+	// Name is the name of the field.
+	Name string
+
+	// Kind is the basic type of the field.
+	Kind Kind
+
+	// Nullable indicates whether null values are accepted for the field.
+	Nullable bool
+
+	// AddressPrefix is the address prefix of the field's kind, currently only used for Bech32AddressKind.
+	AddressPrefix string
+
+	// EnumDefinition is the definition of the enum type and is only valid when Kind is EnumKind.
+	EnumDefinition EnumDefinition
+}

indexer/base/go.mod

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+module cosmossdk.io/indexer/base
+
+// NOTE: this go.mod should have zero dependencies and remain on go 1.12 to stay compatible
+// with all known production releases of the Cosmos SDK. This is to ensure that all historical
+// apps could be patched to support indexing if desired.
+
+go 1.12

indexer/base/kind.go

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+package indexerbase
+
+// Kind represents the basic type of a field in an object.
+// Each kind defines the types of go values which should be accepted
+// by listeners and generated by decoders when providing entity updates.
+type Kind int
+
+const (
+	// InvalidKind indicates that an invalid type.
+	InvalidKind Kind = iota
+
+	// StringKind is a string type and values of this type must be of the go type string
+	// or implement fmt.Stringer().
+	StringKind
+
+	// BytesKind is a bytes type and values of this type must be of the go type []byte.
+	BytesKind
+
+	// Int8Kind is an int8 type and values of this type must be of the go type int8.
+	Int8Kind
+
+	// Uint8Kind is a uint8 type and values of this type must be of the go type uint8.
+	Uint8Kind
+
+	// Int16Kind is an int16 type and values of this type must be of the go type int16.
+	Int16Kind
+
+	// Uint16Kind is a uint16 type and values of this type must be of the go type uint16.
+	Uint16Kind
+
+	// Int32Kind is an int32 type and values of this type must be of the go type int32.
+	Int32Kind
+
+	// Uint32Kind is a uint32 type and values of this type must be of the go type uint32.
+	Uint32Kind
+
+	// Int64Kind is an int64 type and values of this type must be of the go type int64.
+	Int64Kind
+
+	// Uint64Kind is a uint64 type and values of this type must be of the go type uint64.
+	Uint64Kind
+
+	// IntegerKind represents an arbitrary precision integer number. Values of this type must
+	// be of the go type int64, string or a type that implements fmt.Stringer with the resulted string
+	// formatted as an integer number.
+	IntegerKind
+
+	// DecimalKind represents an arbitrary precision decimal or integer number. Values of this type
+	// must be of the go type string or a type that implements fmt.Stringer with the resulting string
+	// formatted as decimal numbers with an optional fractional part. Exponential E-notation
+	// is supported but NaN and Infinity are not.
+	DecimalKind
+
+	// BoolKind is a boolean type and values of this type must be of the go type bool.
+	BoolKind
+
+	// TimeKind is a time type and values of this type must be of the go type time.Time.
+	TimeKind
+
+	// DurationKind is a duration type and values of this type must be of the go type time.Duration.
+	DurationKind
+
+	// Float32Kind is a float32 type and values of this type must be of the go type float32.
+	Float32Kind
+
+	// Float64Kind is a float64 type and values of this type must be of the go type float64.
+	Float64Kind
+
+	// Bech32AddressKind is a bech32 address type and values of this type must be of the go type string or []byte
+	// or a type which implements fmt.Stringer. Fields of this type are expected to set the AddressPrefix field
+	// in the field definition to the bech32 address prefix.
+	Bech32AddressKind
+
+	// EnumKind is an enum type and values of this type must be of the go type string or implement fmt.Stringer.
+	// Fields of this type are expected to set the EnumDefinition field in the field definition to the enum
+	// definition.
+	EnumKind
+
+	// JSONKind is a JSON type and values of this type can either be of go type json.RawMessage
+	// or any type that can be marshaled to JSON using json.Marshal.
+	JSONKind
+)

indexer/base/listener.go

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+package indexerbase
+
+import (
+	"encoding/json"
+)
+
+// Listener is an interface that defines methods for listening to both raw and logical blockchain data.
+// It is valid for any of the methods to be nil, in which case the listener will not be called for that event.
+// Listeners should understand the guarantees that are provided by the source they are listening to and
+// understand which methods will or will not be called. For instance, most blockchains will not do logical
+// decoding of data out of the box, so the InitializeModuleSchema and OnObjectUpdate methods will not be called.
+// These methods will only be called when listening logical decoding is setup.
+type Listener struct {
+	// Initialize is called when the listener is initialized before any other methods are called.
+	// The lastBlockPersisted return value should be the last block height the listener persisted if it is
+	// persisting block data, 0 if it is not interested in persisting block data, or -1 if it is
+	// persisting block data but has not persisted any data yet. This check allows the indexer
+	// framework to ensure that the listener has not missed blocks.
+	Initialize func(InitializationData) (lastBlockPersisted int64, err error)
+
+	// StartBlock is called at the beginning of processing a block.
+	StartBlock func(uint64) error
+
+	// OnBlockHeader is called when a block header is received.
+	OnBlockHeader func(BlockHeaderData) error
+
+	// OnTx is called when a transaction is received.
+	OnTx func(TxData) error
+
+	// OnEvent is called when an event is received.
+	OnEvent func(EventData) error
+
+	// OnKVPair is called when a key-value has been written to the store for a given module.
+	OnKVPair func(moduleName string, key, value []byte, delete bool) error
+
+	// Commit is called when state is committed, usually at the end of a block. Any
+	// indexers should commit their data when this is called and return an error if
+	// they are unable to commit.
+	Commit func() error
+
+	// InitializeModuleSchema should be called whenever the blockchain process starts OR whenever
+	// logical decoding of a module is initiated. An indexer listening to this event
+	// should ensure that they have performed whatever initialization steps (such as database
+	// migrations) required to receive OnObjectUpdate events for the given module. If the
+	// indexer's schema is incompatible with the module's on-chain schema, the listener should return
+	// an error.
+	InitializeModuleSchema func(module string, schema ModuleSchema) error
+
+	// OnObjectUpdate is called whenever an object is updated in a module's state. This is only called
+	// when logical data is available. It should be assumed that the same data in raw form
+	// is also passed to OnKVPair.
+	OnObjectUpdate func(module string, update ObjectUpdate) error
+}
+
+// InitializationData represents initialization data that is passed to a listener.
+type InitializationData struct {
+	// HasEventAlignedWrites indicates that the blockchain data source will emit KV-pair events
+	// in an order aligned with transaction, message and event callbacks. If this is true
+	// then indexers can assume that KV-pair data is associated with these specific transactions, messages
+	// and events. This may be useful for indexers which store a log of all operations (such as immutable
+	// or version controlled databases) so that the history log can include fine grain correlation between
+	// state updates and transactions, messages and events. If this value is false, then indexers should
+	// assume that KV-pair data occurs out of order with respect to transaction, message and event callbacks -
+	// the only safe assumption being that KV-pair data is associated with the block in which it was emitted.
+	HasEventAlignedWrites bool
+}
+
+// BlockHeaderData represents the raw block header data that is passed to a listener.
+type BlockHeaderData struct {
+	// Height is the height of the block.
+	Height uint64
+
+	// Bytes is the raw byte representation of the block header.
+	Bytes ToBytes
+
+	// JSON is the JSON representation of the block header. It should generally be a JSON object.
+	JSON ToJSON
+}
+
+// TxData represents the raw transaction data that is passed to a listener.
+type TxData struct {
+	// TxIndex is the index of the transaction in the block.
+	TxIndex int32
+
+	// Bytes is the raw byte representation of the transaction.
+	Bytes ToBytes
+
+	// JSON is the JSON representation of the transaction. It should generally be a JSON object.
+	JSON ToJSON
+}
+
+// EventData represents event data that is passed to a listener.
+type EventData struct {
+	// TxIndex is the index of the transaction in the block to which this event is associated.
+	// It should be set to a negative number if the event is not associated with a transaction.
+	// Canonically -1 should be used to represent begin block processing and -2 should be used to
+	// represent end block processing.
+	TxIndex int32
+
+	// MsgIndex is the index of the message in the transaction to which this event is associated.
+	// If TxIndex is negative, this index could correspond to the index of the message in
+	// begin or end block processing if such indexes exist, or it can be set to zero.
+	MsgIndex uint32
+
+	// EventIndex is the index of the event in the message to which this event is associated.
+	EventIndex uint32
+
+	// Type is the type of the event.
+	Type string
+
+	// Data is the JSON representation of the event data. It should generally be a JSON object.
+	Data ToJSON
+}
+
+// ToBytes is a function that lazily returns the raw byte representation of data.
+type ToBytes = func() ([]byte, error)
+
+// ToJSON is a function that lazily returns the JSON representation of data.
+type ToJSON = func() (json.RawMessage, error)

indexer/base/module_schema.go

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+package indexerbase
+
+// ModuleSchema represents the logical schema of a module for purposes of indexing and querying.
+type ModuleSchema struct {
+	// ObjectTypes describe the types of objects that are part of the module's schema.
+	ObjectTypes []ObjectType
+}

indexer/base/object_type.go

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+package indexerbase
+
+// ObjectType describes an object type a module schema.
+type ObjectType struct {
+	// Name is the name of the object.
+	Name string
+
+	// KeyFields is a list of fields that make up the primary key of the object.
+	// It can be empty in which case indexers should assume that this object is
+	// a singleton and ony has one value.
+	KeyFields []Field
+
+	// ValueFields is a list of fields that are not part of the primary key of the object.
+	// It can be empty in the case where all fields are part of the primary key.
+	ValueFields []Field
+
+	// RetainDeletions is a flag that indicates whether the indexer should retain
+	// deleted rows in the database and flag them as deleted rather than actually
+	// deleting the row. For many types of data in state, the data is deleted even
+	// though it is still valid in order to save space. Indexers will want to have
+	// the option of retaining such data and distinguishing from other "true" deletions.
+	RetainDeletions bool
+}