added logic to approve-loan message server and added custom error typ…

…e called ErrWrongLoanState in x/loan/types/errors.go

x/loan/keeper/msg_server_approve_loan.go

@@ -4,15 +4,39 @@ import (
 	"context"
 
 	"loan/x/loan/types"
+	errorsmod "cosmossdk.io/errors"
 
 	sdk "github.com/cosmos/cosmos-sdk/types"
+	sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"
 )
 
 func (k msgServer) ApproveLoan(goCtx context.Context, msg *types.MsgApproveLoan) (*types.MsgApproveLoanResponse, error) {
 	ctx := sdk.UnwrapSDKContext(goCtx)
-
-	// TODO: Handling the message
-	_ = ctx
-
+	loan, found := k.GetLoan(ctx, msg.Id)
+	if !found{
+		// cannot find the loan in the blockchain
+		return nil, errorsmod.Wrapf(sdkerrors.ErrKeyNotFound, "key %d doesn't exist", msg.Id)
+	}
+	if loan.Borrower == msg.Creator{
+		// should not be the same one to lend and borrow
+		return nil, errorsmod.Wrap(sdkerrors.ErrConflict, "the borrower and the lender should not be the same one")
+	}
+	if loan.State != "requested"{
+		// check if the state is requested first
+		return nil, errorsmod.Wrapf(types.ErrWrongLoanState, "%v", loan.State)
+	}
+	lender, _ := sdk.AccAddressFromBech32(msg.Creator)
+	borrower, _ := sdk.AccAddressFromBech32(loan.Borrower)
+	amt, err := sdk.ParseCoinsNormalized(loan.Amount)	
+	if err != nil{
+		return nil, errorsmod.Wrap(types.ErrWrongLoanState, "Cannot parse coins in loan amount")
+	}
+	err = k.bankKeeper.SendCoins(ctx, lender, borrower, amt)
+	if err != nil{
+		return nil, err
+	}
+	loan.Lender = msg.Creator
+	loan.State = "approved"
+	k.SetLoan(ctx, loan) 
 	return &types.MsgApproveLoanResponse{}, nil
 }

x/loan/types/errors.go

@@ -10,4 +10,5 @@ import (
 var (
 	ErrInvalidSigner = sdkerrors.Register(ModuleName, 1100, "expected gov account as only signer for proposal message")
 	ErrSample        = sdkerrors.Register(ModuleName, 1101, "sample error")
+	ErrWrongLoanState = sdkerrors.Register(ModuleName, 2, "Wrong loan state")
 )