services/horizon/interal/actions: Drop db2/core dependency in path fi…

…nding actions. (#2675)

- Drop `db2/core` dependency on path finding actions.
- Simplify tests for path finding, removing dependency on pre-built scenario.
- Add mock for `paths.Finder`

### Why

We are in the process of removing Horizon's dependency on `core`'s db. This PR removes such dependency on the path finding end-points and changes the tests to not depend on pre-built SQL scenarios.

This is part of the work to drop `db2/core` (#2643).

services/horizon/internal/actions_path.go

@@ -2,14 +2,15 @@ package horizon
 
 import (
 	"context"
+	"database/sql"
 	"fmt"
 	"net/http"
 	"strings"
 
 	"github.com/stellar/go/amount"
 	"github.com/stellar/go/protocols/horizon"
 	"github.com/stellar/go/services/horizon/internal/actions"
-	"github.com/stellar/go/services/horizon/internal/db2/core"
+	"github.com/stellar/go/services/horizon/internal/db2/history"
 	"github.com/stellar/go/services/horizon/internal/ledger"
 	"github.com/stellar/go/services/horizon/internal/paths"
 	hProblem "github.com/stellar/go/services/horizon/internal/render/problem"
@@ -30,7 +31,7 @@ type FindPathsHandler struct {
 	setLastLedgerHeader  bool
 	maxAssetsParamLength int
 	pathFinder           paths.Finder
-	coreQ                *core.Q
+	historyQ             *history.Q
 }
 
 // StrictReceivePathsQuery query struct for paths/strict-send end-point
@@ -154,9 +155,7 @@ func (handler FindPathsHandler) ServeHTTP(w http.ResponseWriter, r *http.Request
 		sourceAccount := xdr.MustAddress(sourceAccount)
 		query.SourceAccount = &sourceAccount
 		query.ValidateSourceBalance = true
-		query.SourceAssets, query.SourceAssetBalances, err = handler.coreQ.AssetsForAddress(
-			query.SourceAccount.Address(),
-		)
+		query.SourceAssets, query.SourceAssetBalances, err = assetsForAddress(handler.historyQ, query.SourceAccount.Address())
 		if err != nil {
 			problem.Render(ctx, w, err)
 			return
@@ -212,7 +211,7 @@ type FindFixedPathsHandler struct {
 	maxAssetsParamLength int
 	setLastLedgerHeader  bool
 	pathFinder           paths.Finder
-	coreQ                *core.Q
+	historyQ             *history.Q
 }
 
 var destinationAssetsOrDestinationAccount = problem.P{
@@ -320,9 +319,7 @@ func (handler FindFixedPathsHandler) ServeHTTP(w http.ResponseWriter, r *http.Re
 	}
 
 	if destinationAccount != "" {
-		destinationAssets, _, err = handler.coreQ.AssetsForAddress(
-			destinationAccount,
-		)
+		destinationAssets, _, err = assetsForAddress(handler.historyQ, destinationAccount)
 		if err != nil {
 			problem.Render(ctx, w, err)
 			return
@@ -359,3 +356,15 @@ func (handler FindFixedPathsHandler) ServeHTTP(w http.ResponseWriter, r *http.Re
 
 	renderPaths(ctx, records, w)
 }
+
+func assetsForAddress(historyQ *history.Q, addy string) ([]xdr.Asset, []xdr.Int64, error) {
+	err := historyQ.BeginTx(&sql.TxOptions{
+		Isolation: sql.LevelRepeatableRead,
+		ReadOnly:  true,
+	})
+	if err != nil {
+		return nil, nil, err
+	}
+	defer historyQ.Rollback()
+	return historyQ.AssetsForAddress(addy)
+}