package onboarding

import (
	"encoding/json"
	"reflect"
	"strings"
)

// Device tables define every request field as required, including zero-valued
// counters. Go's JSON decoder alone cannot distinguish zero from omission.
func decodeDeviceCall[T any](raw []byte, fn func(T) (map[string]any, error)) (map[string]any, error) {
	var in T
	if err := StrictJSON(raw, &in); err != nil {
		return nil, err
	}
	var fields map[string]json.RawMessage
	if err := json.Unmarshal(raw, &fields); err != nil {
		return nil, err
	}
	v := reflect.ValueOf(in)
	for i := 0; i < v.NumField(); i++ {
		name := strings.Split(v.Type().Field(i).Tag.Get("json"), ",")[0]
		if name == "-" || name == "" {
			continue
		}
		value, present := fields[name]
		if !present || string(value) == "null" {
			return nil, fail(400, "VALIDATION_FAILED", "缺少必填字段："+name)
		}
		if v.Field(i).Kind() == reflect.Int64 || v.Field(i).Kind() == reflect.Int {
			n := v.Field(i).Int()
			minimum := int64(0)
			if name == "sdk_result" {
				minimum = -2147483648
			}
			if n < minimum || n > 2147483647 {
				return nil, fail(400, "VALIDATION_FAILED", "整数超出范围："+name)
			}
		}
	}
	return fn(in)
}