mirgation docs and inital migration

config/env.go

@@ -0,0 +1,78 @@
+// Package config loads platform configuration from the environment.
+//
+// The Env* helpers all follow the same contract: an unset (or empty) variable
+// returns def silently; a variable that is set but unparseable — or rejected by
+// the optional valid predicate — logs once and falls back to def. This keeps the
+// "parse env, validate, log, default" boilerplate out of every cmd/* main.
+package config
+
+import (
+	"log"
+	"os"
+	"strconv"
+	"time"
+)
+
+// EnvString returns the value of key, or def when unset/empty.
+func EnvString(key, def string) string {
+	if v, ok := os.LookupEnv(key); ok && v != "" {
+		return v
+	}
+	return def
+}
+
+// EnvInt parses key as an int, validating with valid (nil = accept any).
+func EnvInt(key string, def int, valid func(int) bool) int {
+	v, ok := os.LookupEnv(key)
+	if !ok || v == "" {
+		return def
+	}
+	n, err := strconv.Atoi(v)
+	if err != nil || (valid != nil && !valid(n)) {
+		log.Printf("invalid %s %q, using %d", key, v, def)
+		return def
+	}
+	return n
+}
+
+// EnvFloat64 parses key as a float64, validating with valid (nil = accept any).
+func EnvFloat64(key string, def float64, valid func(float64) bool) float64 {
+	v, ok := os.LookupEnv(key)
+	if !ok || v == "" {
+		return def
+	}
+	f, err := strconv.ParseFloat(v, 64)
+	if err != nil || (valid != nil && !valid(f)) {
+		log.Printf("invalid %s %q, using %g", key, v, def)
+		return def
+	}
+	return f
+}
+
+// EnvFloat32 parses key as a float32, validating with valid (nil = accept any).
+func EnvFloat32(key string, def float32, valid func(float32) bool) float32 {
+	v, ok := os.LookupEnv(key)
+	if !ok || v == "" {
+		return def
+	}
+	f, err := strconv.ParseFloat(v, 32)
+	if err != nil || (valid != nil && !valid(float32(f))) {
+		log.Printf("invalid %s %q, using %g", key, v, def)
+		return def
+	}
+	return float32(f)
+}
+
+// EnvDuration parses key as a time.Duration (e.g. "2m", "30s").
+func EnvDuration(key string, def time.Duration) time.Duration {
+	v, ok := os.LookupEnv(key)
+	if !ok || v == "" {
+		return def
+	}
+	d, err := time.ParseDuration(v)
+	if err != nil || d <= 0 {
+		log.Printf("invalid %s %q, using %s", key, v, def)
+		return def
+	}
+	return d
+}