lite: add helper functions for initiating the light client (#4486)

* add new net client

* hijack example test

* lint fixes

* reorganised file structure

* renamed funcs and added documentation

* implemented suggested changes

* restored example tests

* edited comments

* Update lite2/setup.go

Co-Authored-By: Bot from GolangCI <42910462+golangcibot@users.noreply.github.com>

* Update lite2/client.go

* lite cmds use HTTP client

* better naming

* Delete go.sum

* Delete go.mod

* restore go mod

* restore go.sum

* fix double import

Co-authored-by: Anton Kaliaev <anton.kalyaev@gmail.com>
Co-authored-by: Bot from GolangCI <42910462+golangcibot@users.noreply.github.com>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

lite2/client.go

@@ -953,11 +953,8 @@ func (c *Client) autoUpdateRoutine() {
 	}
 }
 
-// Update attempts to advance the state making exponential steps (note:
-// when SequentialVerification is being used, the client will still be
-// downloading all intermediate headers).
-//
-// Exposed for testing.
+// Update attempts to advance the state by downloading the latest header and
+// comparing it with the existing one.
 func (c *Client) Update(now time.Time) error {
 	lastTrustedHeight, err := c.LastTrustedHeight()
 	if err != nil {

lite2/example_test.go

@@ -135,7 +135,7 @@ func ExampleClient_VerifyHeaderAtHeight() {
 			Hash:   header.Hash(),
 		},
 		primary,
-		[]provider.Provider{primary}, // TODO: primary should not be used here
+		[]provider.Provider{primary}, // NOTE: primary should not be used here
 		dbs.New(db, chainID),
 		UpdatePeriod(0),
 		// Logger(log.TestingLogger()),

lite2/setup.go

@@ -0,0 +1,77 @@
+package lite
+
+import (
+	"time"
+
+	"github.com/tendermint/tendermint/lite2/provider"
+	"github.com/tendermint/tendermint/lite2/provider/http"
+	"github.com/tendermint/tendermint/lite2/store"
+)
+
+// NewHTTPClient initiates an instance of a lite client using HTTP addresses
+// for both the primary provider and witnesses of the lite client. A trusted
+// header and hash must be passed to initialize the client.
+//
+// See all Option(s) for the additional configuration.
+// See NewClient.
+func NewHTTPClient(
+	chainID string,
+	trustOptions TrustOptions,
+	primaryAddress string,
+	witnessesAddresses []string,
+	trustedStore store.Store,
+	options ...Option) (*Client, error) {
+
+	providers, err := providersFromAddresses(append(witnessesAddresses, primaryAddress), chainID)
+	if err != nil {
+		return nil, err
+	}
+
+	return NewClient(
+		chainID,
+		trustOptions,
+		providers[len(providers)-1],
+		providers[:len(providers)-1],
+		trustedStore,
+		options...)
+}
+
+// NewHTTPClientFromTrustedStore initiates an instance of a lite client using
+// HTTP addresses for both the primary provider and witnesses and uses a
+// trusted store as the root of trust.
+//
+// See all Option(s) for the additional configuration.
+// See NewClientFromTrustedStore.
+func NewHTTPClientFromTrustedStore(
+	chainID string,
+	trustingPeriod time.Duration,
+	primaryAddress string,
+	witnessesAddresses []string,
+	trustedStore store.Store,
+	options ...Option) (*Client, error) {
+
+	providers, err := providersFromAddresses(append(witnessesAddresses, primaryAddress), chainID)
+	if err != nil {
+		return nil, err
+	}
+
+	return NewClientFromTrustedStore(
+		chainID,
+		trustingPeriod,
+		providers[len(providers)-1],
+		providers[:len(providers)-1],
+		trustedStore,
+		options...)
+}
+
+func providersFromAddresses(addrs []string, chainID string) ([]provider.Provider, error) {
+	providers := make([]provider.Provider, len(addrs))
+	for idx, address := range addrs {
+		p, err := http.New(chainID, address)
+		if err != nil {
+			return nil, err
+		}
+		providers[idx] = p
+	}
+	return providers, nil
+}