Quote price in alternate currency

Crypto token price change rapidly.  Make it easier for contributors to
gauge amounts by optionally displaying values in a different currency.

9 files changed, 231 insertions, 21 deletions

diff --git a/asset/template/contribute.html.tmpl b/asset/template/contribute.html.tmpl
index 6efc537..a5fbe25 100644
--- a/asset/template/contribute.html.tmpl
+++ b/asset/template/contribute.html.tmpl
@@ -11,12 +11,19 @@
       <h2>Contribute to "{{toTitle .Objective.Name}}"</h2>
       <ul class="in-short">
         {{if .Objective.IsCrowdMatched}}
-        <li>We ask for <strong>{{.Objective.MinimumLimit.Display}} to {{.Objective.FundingLimit.Display}}</strong>. 🎯
+          <li>We ask for <strong>
+              {{template "money.html.tmpl" .Objective.MinimumLimit}}
+              to
+              {{template "money.html.tmpl" .Objective.FundingLimit}}
+            </strong>. 🎯
         </li>
         {{end}}
-        <li>We raised <strong>{{.Objective.TotalMatched.Display}}</strong>. 🔮
+        <li>We raised
+          <strong>
+            {{template "money.html.tmpl" .Objective.TotalMatched}}
+          </strong>. 🔮
         </li>
-        <li>For matching new contributions, we have <strong>{{.Objective.TotalRefunded.Display}}</strong>. 👫
+        <li>For matching new contributions, we have <strong>{{template "money.html.tmpl" .Objective.TotalRefunded}}</strong>. 👫
         </li>
         {{if .Objective.IsCrowdMatched}}
           <li>Previous contributed amounts will currently be refunded <strong>{{.Objective.TotalRefundedPerc}}</strong>. ↩<li>
@@ -64,7 +71,7 @@
             <div id="contribute-recommended-amounts" class="input-group inline">
               {{range $key, $value := .SuggestedContributions}}
                 <input type="radio" id="amount-{{$key}}" name="Amount" value="{{$value.DisplayAmount}}" {{if eq $key 0}} checked="true" {{end}}>
-                <label for="amount-{{$key}}">{{$value.Display}}</label>
+                <label for="amount-{{$key}}">{{template "money.html.tmpl" $value}}</label>
               {{end}}
             </div>
 
@@ -73,7 +80,7 @@
               <div class="input-group-prefix">{{.Currency}}</div>
               <input type="number" value="{{.SuggestedContribution.DisplayAmount}}" step="{{.SuggestedContributionStep}}" name="AmountCustom" placeholder="e.g: {{.MaxContribution.DisplayAmount}}">
             </div>
-            <p class="instruction"><small>Min: {{.MinContribution.Display}}, Max: {{.MaxContribution.Display}}</small></p>
+            <p class="instruction"><small>Min: {{template "money.html.tmpl" .MinContribution}}, Max: {{template "money.html.tmpl" .MaxContribution}}</small></p>
 
             {{if eq "bitcoin" .TransferMethod}}
               <h3>Refund address</h3>
diff --git a/asset/template/money.html.tmpl b/asset/template/money.html.tmpl
new file mode 100644
index 0000000..8594b7d
--- /dev/null
+++ b/asset/template/money.html.tmpl
@@ -0,0 +1,4 @@
+{{.Display}}
+{{with altCurrency .}}
+  ({{.Display}}) 
+{{end}}
diff --git a/asset/template/project.html.tmpl b/asset/template/project.html.tmpl
index 20be4dd..877210e 100644
--- a/asset/template/project.html.tmpl
+++ b/asset/template/project.html.tmpl
@@ -18,7 +18,10 @@
             <p class="description">{{.ShortDescription}}</p>
             <ul class="stats">
               {{if .IsCrowdMatched}}
-              <li class="stat">🎯 Asking {{.MinimumLimit.Display}} to {{.FundingLimit.Display}}
+              <li class="stat">🎯 Asking
+                    {{template "money.html.tmpl" .MinimumLimit}}
+                  to
+                    {{template "money.html.tmpl" .FundingLimit}}
                 <span class="tooltip">?
                   <span class="tooltip-text">
                     How much is being asked for to start the objective.
@@ -26,7 +29,8 @@
                 </span>
               </li>
               {{end}}
-              <li class="stat">🔮 Raised {{.TotalMatched.Display}}
+              <li class="stat">🔮 Raised
+                {{template "money.html.tmpl" .TotalMatched}}
                 <span class="tooltip">?
                   <span class="tooltip-text">
                     Total non-refunded value raised from all contributions.
diff --git a/config.go b/config.go
index dcd3576..c9e9bfd 100644
--- a/config.go
+++ b/config.go
@@ -103,13 +103,16 @@ type Config struct {
 	ProjectDirectory       *string `yaml:"project-directory,omitempty"`
 	ServiceAgreementEnable *bool   `yaml:"service-agreement-enable,omitempty"`
 	ServiceAgreementFile   *string `yaml:"service-agreement-file,omitempty"`
-	SMTPAddress            *string `yaml:"smtp-address,omitempty"`
-	SMTPNotifyContribution *bool   `yaml:"smtp-notify-contribution,omitempty"`
-	SMTPPassword           *string `yaml:"smtp-password,omitempty"`
-	SMTPRecipients         *string `yaml:"smtp-recipients,omitempty"`
-	SMTPUser               *string `yaml:"smtp-user,omitempty"`
+	// ShowAlternativeCurrency will show money in an additional currency to
+	// aid users when dealing with crypto tokens.
+	ShowAlternativeCurrency *string `yaml:"show-alternative-currency"`
+	SMTPAddress             *string `yaml:"smtp-address,omitempty"`
+	SMTPNotifyContribution  *bool   `yaml:"smtp-notify-contribution,omitempty"`
+	SMTPPassword            *string `yaml:"smtp-password,omitempty"`
+	SMTPRecipients          *string `yaml:"smtp-recipients,omitempty"`
+	SMTPUser                *string `yaml:"smtp-user,omitempty"`
 	// SuggestedContributions is a list of recommended amounts when contributing.
-	SuggestedContributions map[string][]decimal.Decimal `yaml:"suggested-contributions"`
+	SuggestedContributions map[string][]decimal.Decimal `yaml:"suggested-contributions,omitempty"`
 	// TestPaymentGatewayEnable enables an always successful payment
 	// gateway which accepts all currencies.
 	//
diff --git a/external/coingecko.go b/external/coingecko.go
new file mode 100644
index 0000000..ad773a9
--- /dev/null
+++ b/external/coingecko.go
@@ -0,0 +1,145 @@
+package external
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net"
+	"net/http"
+	"strings"
+	"sync"
+	"time"
+
+	"git.server.ky/cypher/librefund"
+	"git.server.ky/cypher/librefund/payment/bitcoin"
+	"github.com/Rhymond/go-money"
+	"github.com/pkg/errors"
+	"github.com/shopspring/decimal"
+)
+
+const coingeckoAPI = "https://api.coingecko.com/api/v3/simple/price"
+
+type symbolPair struct {
+	From string
+	To   string
+}
+
+func (s symbolPair) Swap() symbolPair {
+	return symbolPair{
+		From: s.To,
+		To:   s.From,
+	}
+}
+func (s symbolPair) String() string {
+	return fmt.Sprintf("(%s, %s)", s.From, s.To)
+}
+
+func (s *symbolPair) UnmarshalText() string {
+	return fmt.Sprintf("(%s, %s)", s.From, s.To)
+
+}
+
+// CoinGecko is a quick and dirty solution to fetch BTC prices without
+// importing a supporting package.
+//
+// It is configured to use IPv4 for HTTP requests to avoid rate limiting.
+type CoinGecko struct {
+	mut sync.Mutex
+
+	client      *http.Client
+	interval    time.Duration
+	lastupdated map[symbolPair]time.Time
+	price       map[symbolPair]decimal.Decimal
+}
+
+func NewCoinGecko() *CoinGecko {
+	s := &CoinGecko{
+		interval:    time.Minute,
+		lastupdated: make(map[symbolPair]time.Time),
+		price:       make(map[symbolPair]decimal.Decimal),
+	}
+	s.setupHttpClient()
+
+	return s
+}
+
+func (s *CoinGecko) setupHttpClient() {
+	client := &http.Client{
+		Timeout: 5 * time.Second,
+	}
+
+	var zeroDialer net.Dialer
+	transport := http.DefaultTransport.(*http.Transport).Clone()
+	transport.DialContext = func(ctx context.Context, network, addr string) (net.Conn, error) {
+		return zeroDialer.DialContext(ctx, "tcp4", addr)
+	}
+	client.Transport = transport
+	s.client = client
+}
+
+func (s *CoinGecko) updatePrice(pair symbolPair) error {
+	if pair.From != "BTC" {
+		return errors.New("only BTC supported")
+	}
+
+	p := fmt.Sprintf("%s?ids=%s&vs_currencies=%s", coingeckoAPI, "bitcoin", pair.To)
+	resp, err := s.client.Get(p)
+	if err != nil {
+		return err
+	}
+	if resp.StatusCode != http.StatusOK {
+		return errors.New("bad status code")
+	}
+
+	payload := make(map[string]map[string]decimal.Decimal)
+	err = json.NewDecoder(resp.Body).Decode(&payload)
+	if err != nil {
+		return err
+	}
+
+	v, ok := payload["bitcoin"]
+	if !ok {
+		return errors.New("malformated payload")
+	}
+	v2, ok := v[strings.ToLower(pair.To)]
+	if !ok {
+		return errors.New("malformated payload")
+	}
+
+	s.price[pair] = v2
+	s.lastupdated[pair] = time.Now()
+	return nil
+}
+
+// GetPrice returns the estimated value for the amount in the given
+// currency.
+func (s *CoinGecko) QuotePrice(curCode string, amount *librefund.Money) (*librefund.Money, error) {
+	s.mut.Lock()
+	defer s.mut.Unlock()
+
+	inCur := money.GetCurrency(curCode)
+	pair := symbolPair{
+		From: amount.Currency().Code,
+		To:   inCur.Code,
+	}
+	if pair.From != bitcoin.CurrencyCode {
+		return nil, errors.New("can only convert BTC")
+	}
+
+	lastupdate, ok := s.lastupdated[pair]
+	if !ok || time.Now().Sub(lastupdate) > s.interval {
+		err := s.updatePrice(pair)
+		if err != nil {
+			return nil, err
+		}
+	}
+	price := s.price[pair]
+
+	convAmount := librefund.Decimal(amount).Mul(price)
+	convAmount = convAmount.Round(int32(inCur.Fraction))
+	conv, err := librefund.NewMoneyFromDecimal(convAmount, inCur.Code)
+	if err != nil {
+		return nil, errors.Wrapf(err, "getting price for %s", pair)
+	}
+	return conv, nil
+}
diff --git a/external/coingecko_test.go b/external/coingecko_test.go
new file mode 100644
index 0000000..fa2d3a9
--- /dev/null
+++ b/external/coingecko_test.go
@@ -0,0 +1,15 @@
+package external
+
+import (
+	"testing"
+
+	"git.server.ky/cypher/librefund"
+	"github.com/stretchr/testify/require"
+)
+
+func TestCoinGeckoGetPrice(t *testing.T) {
+	cg := NewCoinGecko()
+	convAmount, err := cg.QuotePrice("USD", librefund.MustMoney("1", "BTC"))
+	require.NoError(t, err, "interfacing with coingecko should be ok")
+	require.NotZero(t, convAmount.Amount(), "expect conversion to sane amount")
+}
diff --git a/http/html_template.go b/http/html_template.go
index 68ccc29..c4c22e4 100644
--- a/http/html_template.go
+++ b/http/html_template.go
@@ -18,18 +18,32 @@ import (
 	"github.com/shopspring/decimal"
 )
 
+func AltCurrency(
+	pricer service.QuotePricer,
+	curCode *string,
+) func(*librefund.Money) *librefund.Money {
+	return func(arg *librefund.Money) *librefund.Money {
+		if curCode == nil {
+			return nil
+		}
+		res, _ := pricer.QuotePrice(*curCode, arg)
+		return res
+	}
+}
+
 func ToTitle(arg string) string {
 	title := strings.ReplaceAll(arg, "-", " ")
 	title = strings.Title(title)
 	return title
 }
 
-func initTemplates(h *HTTPServer) (*template.Template, error) {
+func initTemplates(cfg *librefund.Config, h *HTTPServer) (*template.Template, error) {
 	funcMap := template.FuncMap{
-		"add":       add,
-		"qrcodeURL": h.qrcodeURL,
-		"url":       h.url,
-		"toTitle":   ToTitle,
+		"add":         add,
+		"altCurrency": AltCurrency(h.srv, h.srv.Config.ShowAlternativeCurrency),
+		"qrcodeURL":   h.qrcodeURL,
+		"url":         h.url,
+		"toTitle":     ToTitle,
 	}
 
 	entries, err := librefund.AssetDir.ReadDir("asset/template")
@@ -145,6 +159,7 @@ type tplObjective struct {
 func newTPLObjective(
 	cfg *librefund.Config,
 	obj *librefund.Objective,
+	quotePricer service.QuotePricer,
 ) (*tplObjective, error) {
 	tObj := tplObjective{
 		Objective: obj,
@@ -164,6 +179,7 @@ func newTPLObjective(
 	if err != nil {
 		return nil, err
 	}
+
 	return &tObj, nil
 }
 
@@ -228,7 +244,7 @@ func newTPLGetProjectFields(
 	}
 	sort.Sort(objectivesByName(objs))
 	for _, v := range objs {
-		obj, err := newTPLObjective(&srv.Config, v)
+		obj, err := newTPLObjective(&srv.Config, v, srv)
 		if err != nil {
 			return nil, err
 		}
@@ -424,7 +440,7 @@ func newTPLContributeFields(
 	if err != nil {
 		return nil, err
 	}
-	ret.Objective, err = newTPLObjective(&srv.Config, obj)
+	ret.Objective, err = newTPLObjective(&srv.Config, obj, srv)
 	if err != nil {
 		return nil, err
 	}
diff --git a/http/http.go b/http/http.go
index 789270a..f1f6f73 100644
--- a/http/http.go
+++ b/http/http.go
@@ -114,7 +114,7 @@ func (h *HTTPServer) initRoutes() error {
 	h.router = mux.NewRouter()
 
 	var err error
-	h.templates, err = initTemplates(h)
+	h.templates, err = initTemplates(&h.srv.Config, h)
 	if err != nil {
 		return err
 	}
diff --git a/service/service.go b/service/service.go
index c883ac6..417fdcb 100644
--- a/service/service.go
+++ b/service/service.go
@@ -12,6 +12,7 @@ import (
 	"time"
 
 	"git.server.ky/cypher/librefund"
+	"git.server.ky/cypher/librefund/external"
 	"git.server.ky/cypher/librefund/payment"
 	"git.server.ky/cypher/librefund/payment/bitcoin"
 	"git.server.ky/cypher/librefund/payment/taler"
@@ -27,6 +28,11 @@ const ConfigPath = "etc/librefund.yaml"
 // refundDeadline is a safety duration added to a payments refund deadline.
 const refundDeadline = 7 * 24 * time.Hour
 
+// QuotePricer returns the conversion amount of a given currency amount.
+type QuotePricer interface {
+	QuotePrice(curCode string, base *librefund.Money) (*librefund.Money, error)
+}
+
 // TransferMethodFor returns the supported transfer method for the given
 // currency.
 //
@@ -52,6 +58,7 @@ type Service struct {
 
 	Config librefund.Config
 
+	// payments
 	bitcoinPG *bitcoin.PaymentGateway
 	taler     *talerAdapter.Adapter
 	testPG    *payment.TestPaymentGateway
@@ -70,6 +77,7 @@ type Service struct {
 	agreementsFile *os.File
 	eventLog       *librefund.EventLog
 	maintainerUI   *librefund.FileSystemUserInterface
+	quotePricer    QuotePricer
 	scheduler      *Scheduler
 	smtpNotifier   *SMTPNotifier
 	store          *librefund.FileSystemStore
@@ -106,6 +114,8 @@ func NewService(cfg librefund.Config) (*Service, error) {
 		return nil, err
 	}
 
+	ret.quotePricer = external.NewCoinGecko()
+
 	ret.scheduler = NewScheduler()
 	ret.scheduler.RunEvery(5*time.Minute, ret.refreshProjectInfo)
 
@@ -783,6 +793,12 @@ func (s *Service) ContributeBitcoin(
 	return payInfo, nil
 }
 
+// QuotePrice returns the last known quoted conversion amount to the given
+// currency.
+func (s *Service) QuotePrice(curCode string, base *librefund.Money) (*librefund.Money, error) {
+	return s.quotePricer.QuotePrice(curCode, base)
+}
+
 func (s *Service) GetProjectContributions(
 	project string,
 	count, offset int,