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(define-module (hnh util object)
:use-module (srfi srfi-9 gnu)
:use-module (ice-9 curried-definitions)
:use-module (hnh util)
:use-module (hnh util type)
:export (define-type))
;; If given a syntax list extract the first lexeme, if given a "symbol", return that.
(define (syntax-first stx)
(syntax-case stx ()
((a rest ...) #'a)
(a #'a)))
(define (construct-syntax stx base transform)
(->> base
syntax->datum
(format #f transform)
string->symbol
(datum->syntax stx)))
;; stx should be a syntax object of a key-value list on the form
;; (key: value key2: value2)
;; and target-key the datum which the target key unwraps to.
;; returns the corresponding values syntax
;; or #f if none is found
(define (kv-ref stx target-key)
(syntax-case stx ()
((key value rest ...)
(if (eqv? target-key (syntax->datum #'key))
#'value
(kv-ref #'(rest ...) target-key)))
(_ #f)))
;; Given (x type: predicate?), expand to a single `unless' form (otherwise #f)
;; Each variable gets its own unless form, to enable better error messages
(define-syntax (validator stx)
(syntax-case stx ()
;; This form may be expanded both from the constructor, and from
;; accessor procedures.
;; In the constructor a different name may be used for the variable,
;; due to custom keyword arguments being a thing.
;; The field `name*' represents the variable holding the value
;; While the field `name' contains the true name of the field in the struct.
((_ name* (name kvs ...))
(cond ((kv-ref #'(kvs ...) type:)
=> (lambda (type-stx)
(with-syntax ((type type-stx))
#'(unless (build-validator-body name* type)
(scm-error 'wrong-type-arg "validator"
"Invalid value for `~s'. Expected ~s, got ~s"
(list (quote name) (quote type) name*) #f)))))
(else #f)))
((_ name) #f)))
;;; When constructing a validator from a type constructor the keyword:
;;; key in the field declaration should be honored. This means that the
;;; looked at name, and the "true name" of a field may differ.
(define-syntax (constructor-validator stx)
(syntax-case stx ()
((_ (name kvs ...))
(with-syntax ((name*
(cond ((kv-ref #'(kvs ...) keyword:)
=> identity)
(else #'name))))
#'(validator name* (name kvs ...))))
((_ name) #f)))
;; Get syntax for getter-procedure's symbol
(define-syntax (field-get stx)
(syntax-case stx ()
;; ((_ (name kv ...)) #'(field-get name))
((_ type-name name)
(->>
(format #f "~a-~a-get"
(syntax->datum #'type-name)
(syntax->datum #'name))
string->symbol
(datum->syntax stx)))))
;; get syntax for setter-procedure's symbol
(define-syntax (field-set stx)
(syntax-case stx ()
;; ((_ (name kv ...)) #'(field-set name))
((_ type-name name)
(->>
(format #f "~a-~a-set"
(syntax->datum #'type-name)
(syntax->datum #'name))
string->symbol
(datum->syntax stx)))))
;; Construct a field line for define-immutable-record-type
(define ((field-declaration type) stx)
(syntax-case stx ()
(name
(with-syntax ((name-get (->> (format #f "~a-~a-get"
(syntax->datum type)
(syntax->datum #'name))
string->symbol
(datum->syntax stx)))
(name-set (->> (format #f "~a-~a-set"
(syntax->datum type)
(syntax->datum #'name))
string->symbol
(datum->syntax stx))))
#'(name name-get name-set)))))
;; Accessors are procedures for getting and setting fields in records
(define-syntax (build-accessor stx)
(syntax-case stx ()
((_ type-name (name kvs ...))
#'(define name
(case-lambda ((datum)
((field-get type-name name) datum))
((datum new-value)
;; validator uses the first field (in the list) as both
;; the name of the field, and a reference to the value of
;; the field. This ensures those two are the same for validator,
;; while keeping name bound to the accessor in the outer scope.
(let ((name new-value))
(validator name (name kvs ...)))
((field-set type-name name) datum new-value)))))
((_ type-name name) #'(build-accessor type-name (name)))))
(define (syntax-name field)
(syntax-case field ()
((name kvs ...)
(cond ((kv-ref #'(kvs ...) keyword:)
=> identity)
(else #'name)))
(name #'name)))
;; Go from my concept of field definitions, to what lambda* wants as arguments
(define (lambda*-stx field)
(syntax-case field ()
((name kvs ...)
(cond ((kv-ref #'(kvs ...) default:)
=> (lambda (dflt) #`(#,(syntax-name field) #,dflt)))
(else (syntax-name field))))
(name #'name)))
(define-syntax (define-type stx)
(syntax-case stx ()
((_ (name attribute ...) field ...)
;; These names SHOULD leak
(with-syntax ((<type>? (construct-syntax stx #'name "~a?")))
;; These names are manually constructed, since generated identifiers are
;; only dependant on the source from which they orginate, which leads to
;; multiple instances of <type> being equal for similar types...
;; See the manual 6.10.10 Hygiene and the Top-Level
;; They technically shouldn't be exposed, but are as a side effect.
(with-syntax ((<type> (construct-syntax stx #'name "<~a>"))
(make-<type> (construct-syntax stx #'name "make-~a%")))
#`(begin
;; Define actual type
(define-immutable-record-type <type>
(make-<type> #,@(map syntax-first #'(field ...)))
<type>?
#,@(map (field-declaration #'name)
(map syntax-first #'(field ...))))
;; User-facing constructor
(define name
#,(cond ((kv-ref #'(attribute ...) constructor:)
=> (lambda (constructor-builder)
#`(#,constructor-builder
;; primitive constructor
make-<type>
;; Type validator
(lambda #,(map syntax-first #'(field ...))
(constructor-validator field) ...))))
(else #`(lambda* (key: #,@(map lambda*-stx #'(field ...)))
;; Type validators
(constructor-validator field) ...
(make-<type> #,@(map syntax-name #'(field ...)))))))
;; Field accessors
(build-accessor name field) ...
;; if printer in attribute
#,@(cond ((kv-ref #'(attribute ...) printer:)
=> (lambda (printer)
(list #`(set-record-type-printer! <type> #,printer))))
(else '()))))))
;; else, type name without extra attributes
#;
((_ name field ...)
#'(define-type (name) field ...))))
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