http/req: moves parsing/validating functionality into ParseBody and P…

…arseQueryParams

http/req/decode.go

@@ -9,35 +9,18 @@ import (
 	"github.com/xy-planning-network/trails"
 )
 
-type queryParamDecoder struct {
-	decoder *schema.Decoder
-}
-
-func newQueryParamDecoder() queryParamDecoder {
+func newQueryParamDecoder() *schema.Decoder {
 	dec := schema.NewDecoder()
 	dec.IgnoreUnknownKeys(true)
 
-	return queryParamDecoder{dec}
+	return dec
 }
 
-// Decode translates src into dst.
-// Upon success, dst holds all values in src that match to fields in dst.
-//
-// On failure, Decode can return a host of errors.
-// Some errors are issues with calling code;
+// translateDecoderError converts an error returned by *schema.Decoder into standardized errors.
+// Some *schema.Decoder errors are issues with calling code;
 // some errors are unexpected issues;
-// still some are issues with src's keys or values not matching dst.
-// In the last case,
-func (q queryParamDecoder) decode(dst any, src map[string][]string) error {
-	err := q.decoder.Decode(dst, src)
-	if err == nil {
-		return nil
-	}
-
-	if err.Error() == "schema: interface must be a pointer to struct" {
-		return fmt.Errorf("%w: called with non-pointer: %s", trails.ErrBadAny, err)
-	}
-
+// still some are issues with mismatches between a request's query params and the expected shape.
+func translateDecoderError(err error) error {
 	var pkgErrs schema.MultiError
 	// NOTE(dlk): In testing the schema package, outside other errors handled above,
 	// the package appears to always use MultiError to wrap errors up.

http/req/req.go

@@ -7,12 +7,18 @@ import (
 	"io"
 	"net/url"
 
+	v10 "github.com/go-playground/validator/v10"
+	"github.com/gorilla/schema"
 	"github.com/xy-planning-network/trails"
 )
 
+const (
+	failedValidationTmpl = "trails/http/req: %T failed validation: %w"
+)
+
 type Parser struct {
-	queryParamDecoder queryParamDecoder
-	validator
+	queryParamDecoder *schema.Decoder
+	validator         *v10.Validate
 }
 
 func NewParser() *Parser {
@@ -29,18 +35,28 @@ func NewParser() *Parser {
 // ParseBody reads the entire r.Body and can't be read from again.
 // Use a [io.TeeReader] if r.Body needs to be reused after calling ParseBody.
 func (p *Parser) ParseBody(body io.Reader, structPtr any) error {
-	var ourFault *json.InvalidUnmarshalError
 	err := json.NewDecoder(body).Decode(structPtr)
+
+	var ourFault *json.InvalidUnmarshalError
 	if errors.As(err, &ourFault) {
-		return fmt.Errorf("trails/http/req: %w: ParseBody called with non-pointer: %s", trails.ErrBadAny, err)
+		return fmt.Errorf("trails/http/req: %w: ParseBody called with non-pointer", trails.ErrBadAny)
 	}
 
 	if err != nil {
 		return fmt.Errorf("trails/http/req: %w: failed decoding request body: %s", trails.ErrBadFormat, err)
 	}
 
-	if err := p.validate(structPtr); err != nil {
-		return fmt.Errorf("trails/http/req: %T failed validation: %w", structPtr, err)
+	err = p.validator.Struct(structPtr)
+
+	var verrs v10.ValidationErrors
+	if errors.As(err, &verrs) {
+		err = translateValidationErrors(verrs)
+		return fmt.Errorf(failedValidationTmpl, structPtr, err)
+	}
+
+	if err != nil {
+		// NOTE(dlk): return raw v10.Validator errors until use cases show up for parsing these differently.
+		return err
 	}
 
 	return nil
@@ -50,12 +66,33 @@ func (p *Parser) ParseBody(body io.Reader, structPtr any) error {
 // If successful, ParseQueryParams runs validation against the contents,
 // returning an ErrNotValid if the data fails validation rules.
 func (p *Parser) ParseQueryParams(params url.Values, structPtr any) error {
-	if err := p.queryParamDecoder.decode(structPtr, params); err != nil {
+	err := p.queryParamDecoder.Decode(structPtr, params)
+	if err != nil {
+		if err.Error() == "schema: interface must be a pointer to struct" {
+			err = fmt.Errorf("trails/http/req: %w: ParseQueryParams called with non-pointer", trails.ErrBadAny)
+
+			return err
+		}
+
+		err = translateDecoderError(err)
+		if errors.Is(err, trails.ErrNotValid) {
+			return fmt.Errorf(failedValidationTmpl, structPtr, err)
+		}
+
 		return fmt.Errorf("trails/http/req: failed decoding request query params: %w", err)
 	}
 
-	if err := p.validate(structPtr); err != nil {
-		return fmt.Errorf("trails/http/req: %T failed validation: %w", structPtr, err)
+	err = p.validator.Struct(structPtr)
+
+	var verrs v10.ValidationErrors
+	if errors.As(err, &verrs) {
+		err = translateValidationErrors(verrs)
+		return fmt.Errorf(failedValidationTmpl, structPtr, err)
+	}
+
+	if err != nil {
+		// NOTE(dlk): return raw v10.Validator errors until use cases show up for parsing these differently.
+		return err
 	}
 
 	return nil

http/req/validate.go

@@ -1,20 +1,15 @@
 package req
 
 import (
-	"errors"
 	"reflect"
 	"strings"
 
 	v10 "github.com/go-playground/validator/v10"
 	"github.com/xy-planning-network/trails"
 )
 
-type validator struct {
-	valid *v10.Validate
-}
-
 // newValidator constructs a validator, which applies default configuration.
-func newValidator() validator {
+func newValidator() *v10.Validate {
 	v := v10.New()
 	v.RegisterValidation("enum", validateEnumerable)
 	v.RegisterTagNameFunc(func(field reflect.StructField) string {
@@ -34,24 +29,12 @@ func newValidator() validator {
 		return name
 	})
 
-	return validator{v}
+	return v
 }
 
-// validate checks the fields on structPtr match the rules set by "validate" struct tags.
-// On success, validate returns no error.
-// On failure, validate translates each issue to a ValidationError,
+// translateValidationErrors converts each issue into a ValidationError,
 // returning them all as ValidationErrors.
-func (v validator) validate(structPtr any) error {
-	err := v.valid.Struct(structPtr)
-	if err == nil {
-		return nil
-	}
-
-	var errs v10.ValidationErrors
-	if !errors.As(err, &errs) {
-		return err
-	}
-
+func translateValidationErrors(errs v10.ValidationErrors) error {
 	var validateErrs ValidationErrors
 	for _, ve := range errs {
 		field := ve.Namespace()