feat: exporter api, json exporter

internal/adapters/exporter/exporter.go

@@ -0,0 +1,43 @@
+package exporter
+
+import (
+	"context"
+	"fmt"
+	"github.com/abelith/spellbook/internal/models"
+	"io"
+	"sync"
+)
+
+type Exporter interface {
+	Export(ctx context.Context, ch <-chan models.Spell, w io.Writer) error
+}
+
+var (
+	exporters = make(map[string]Exporter)
+	mu        sync.Mutex
+)
+
+func Register(name string, exp Exporter) {
+	mu.Lock()
+	defer mu.Unlock()
+
+	if exp == nil {
+		panic("exporter: Exporter cannot be nil")
+	}
+	if _, ok := exporters[name]; ok {
+		panic("exporter: Register called twice for " + name)
+	}
+	exporters[name] = exp
+}
+
+func Export(ctx context.Context, name string, ch <-chan models.Spell, w io.Writer) error {
+	mu.Lock()
+	exp, ok := exporters[name]
+	mu.Unlock()
+
+	if !ok {
+		return fmt.Errorf("exporter %s not found", name)
+	}
+
+	return exp.Export(ctx, ch, w)
+}