ddnnss

Signed-off-by: Mel <mel@rnrd.eu>

1 files changed, 91 insertions, 0 deletions

diff --git a/source/source.go b/source/source.go
new file mode 100644
index 0000000..6fe139c
--- /dev/null
+++ b/source/source.go
@@ -0,0 +1,91 @@
+package source
+
+import (
+	"fmt"
+	"io"
+	"log/slog"
+	"net/http"
+	"net/netip"
+	"strings"
+	"time"
+)
+
+type Kind string
+
+const (
+	// only the simple generic sources for now!
+	KindStatic Kind = "static"
+	KindURL    Kind = "url"
+	KindFile   Kind = "file"
+)
+
+type Family string
+
+const (
+	IPv4 Family = "ipv4"
+	IPv6 Family = "ipv6"
+)
+
+type Config struct {
+	Kind   Kind   `json:"kind"`
+	Family Family `json:"family,omitempty"`
+
+	URL   string `json:"url,omitempty"`
+	Path  string `json:"path,omitempty"`
+	Value string `json:"value,omitempty"`
+}
+
+type Source interface {
+	Supports(Family) bool
+	Lookup(Family) (netip.Addr, error)
+}
+
+func New(log *slog.Logger, cfg Config) (Source, error) {
+	if cfg.Family != IPv4 && cfg.Family != IPv6 {
+		return nil, fmt.Errorf("%s source needs family set to ipv4 or ipv6", cfg.Kind)
+	}
+
+	if cfg.Kind == KindStatic {
+		return newStatic(log, cfg)
+	}
+
+	if cfg.Kind == KindURL {
+		return newURL(log, cfg)
+	}
+
+	if cfg.Kind == KindFile {
+		return newFile(log, cfg)
+	}
+
+	return nil, fmt.Errorf("unknown source kind %q", cfg.Kind)
+}
+
+// parsing function for ipv4 and ipv6 strings
+func parse(raw string, family Family) (netip.Addr, error) {
+	addr, err := netip.ParseAddr(strings.TrimSpace(raw))
+	if err != nil {
+		return netip.Addr{}, err
+	}
+	if addr.Is6() != (family == IPv6) {
+		return netip.Addr{}, fmt.Errorf("%s is not an %s address", addr, family)
+	}
+	return addr, nil
+}
+
+// generic http fetching helper since a lot of sources will need it.
+func fetch(url string, family Family) (netip.Addr, error) {
+	client := http.Client{Timeout: 15 * time.Second}
+	resp, err := client.Get(url)
+	if err != nil {
+		return netip.Addr{}, err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return netip.Addr{}, fmt.Errorf("%s: %s", url, resp.Status)
+	}
+	raw, err := io.ReadAll(io.LimitReader(resp.Body, 256))
+	if err != nil {
+		return netip.Addr{}, err
+	}
+	return parse(string(raw), family)
+}