#lang racket/base
(require (for-syntax racket/base
                     yaragg/parser-tools/private-yacc/parser-builder
                     yaragg/parser-tools/private-yacc/grammar
                     yaragg/parser-tools/private-yacc/yacc-helper
                     yaragg/parser-tools/private-yacc/parser-actions)
         yaragg/parser-tools/private-lex/token
         yaragg/parser-tools/private-yacc/parser-actions
         racket/local
         racket/pretty
         syntax/readerr)

(provide parser)


;; convert-parse-table : (vectorof (listof (cons/c gram-sym? action?))) ->
;;                       (vectorof (symbol runtime-action hashtable))
(define-for-syntax (convert-parse-table table)
  (for/vector ([state-entry (in-vector table)])
    (let ([ht (make-hasheq)])
      (for ([gs/action (in-list state-entry)])
        (hash-set! ht
                   (gram-sym-symbol (car gs/action))
                   (action->runtime-action (cdr gs/action))))
      ht)))
  
(define-syntax (parser stx)
  (syntax-case stx ()
    [(_ ARGS ...)
     (let ([arg-list (syntax->list #'(ARGS ...))]
           [src-pos #f]
           [debug #f]
           [error #f]
           [tokens #f]
           [start #f]
           [end #f]
           [precs #f]
           [suppress #f]
           [grammar #f]
           [yacc-output #f])
       (for ([arg (in-list (syntax->list #'(ARGS ...)))])
         (syntax-case* arg (debug error tokens start end precs grammar
                                  suppress src-pos yacc-output)
           (λ (a b) (eq? (syntax-e a) (syntax-e b)))
           [(debug FILENAME)
            (cond
              [(not (string? (syntax-e #'FILENAME)))
               (raise-syntax-error #f "Debugging filename must be a string" stx #'FILENAME)]
              [debug (raise-syntax-error #f "Multiple debug declarations" stx)]
              [else (set! debug (syntax-e #'FILENAME))])]
           [(suppress) (set! suppress #t)]
           [(src-pos) (set! src-pos #t)]
           [(error EXPRESSION)
            (if error
                (raise-syntax-error #f "Multiple error declarations" stx)
                (set! error #'EXPRESSION))]
           [(tokens DEF ...)
            (begin
              (when tokens
                (raise-syntax-error  #f "Multiple tokens declarations" stx))
              (let ((defs (syntax->list #'(DEF ...))))
                (for ([d (in-list defs)]
                      #:unless (identifier? d))
                  (raise-syntax-error #f "Token-group name must be an identifier" stx d))
                (set! tokens defs)))]
           [(start symbol ...)
            (let ([symbols (syntax->list #'(symbol ...))])
              (for ([sym (in-list symbols)]
                    #:unless (identifier? sym))
                (raise-syntax-error #f "Start symbol must be a symbol" stx sym))
              (when start
                (raise-syntax-error #f "Multiple start declarations" stx))
              (when (null? symbols)
                (raise-syntax-error #f "Missing start symbol" stx arg))
              (set! start symbols))]
           [(end SYMBOLS ...)
            (let ((symbols (syntax->list #'(SYMBOLS ...))))
              (for ([sym (in-list symbols)]
                    #:unless (identifier? sym))
                (raise-syntax-error #f "End token must be a symbol" stx sym))
              (let ([d (duplicate-list? (map syntax-e symbols))])
                (when d
                  (raise-syntax-error #f (format "Duplicate end token definition for ~a" d) stx arg))
                (when (null? symbols)
                  (raise-syntax-error #f "end declaration must contain at least 1 token" stx arg))
                (when end
                  (raise-syntax-error #f "Multiple end declarations" stx))
                (set! end symbols)))]
           [(precs DECLS ...)
            (if precs
                (raise-syntax-error #f "Multiple precs declarations" stx)
                (set! precs (syntax/loc arg (DECLS ...))))]
           [(grammar PRODS ...)
            (if grammar
                (raise-syntax-error #f "Multiple grammar declarations" stx)
                (set! grammar (syntax/loc arg (PRODS ...))))]
           [(yacc-output FILENAME)
            (cond
              [(not (string? (syntax-e #'FILENAME)))
               (raise-syntax-error #f "Yacc-output filename must be a string" stx #'FILENAME)]
              [yacc-output
               (raise-syntax-error #f "Multiple yacc-output declarations" stx)]
              [else
               (set! yacc-output (syntax-e #'FILENAME))])]
           [_ (raise-syntax-error #f "argument must match (debug filename), (error expression), (tokens def ...), (start non-term), (end tokens ...), (precs decls ...), or  (grammar prods ...)" stx arg)]))
       (unless tokens
         (raise-syntax-error #f "missing tokens declaration" stx))
       (unless error
         (raise-syntax-error #f "missing error declaration" stx))
       (unless grammar
         (raise-syntax-error #f "missing grammar declaration" stx))
       (unless end
         (raise-syntax-error #f "missing end declaration" stx))
       (unless start
         (raise-syntax-error #f "missing start declaration" stx))
       (let-values ([(table all-term-syms actions check-syntax-fix)
                     (build-parser (if debug debug "")
                                   src-pos
                                   suppress
                                   tokens
                                   start
                                   end
                                   precs
                                   grammar)])
         (when (and yacc-output (not (string=? yacc-output "")))
           (with-handlers [(exn:fail:filesystem?
                            (λ (e) (eprintf "Cannot write yacc-output to file \"~a\"\n" yacc-output)))]
             (call-with-output-file yacc-output
               (λ (port)
                 (display-yacc (syntax->datum grammar) 
                               tokens 
                               (map syntax->datum start)
                               (and precs (syntax->datum precs))
                               port))
               #:exists 'truncate)))
         (with-syntax ([check-syntax-fix check-syntax-fix]
                       [err error]
                       [ends end]
                       [starts start]
                       [debug debug]
                       [table (convert-parse-table table)]
                       [all-term-syms all-term-syms]
                       [actions actions]
                       [src-pos src-pos])
           #'(begin
               check-syntax-fix
               (parser-body debug err (quote starts) (quote ends) table all-term-syms actions src-pos)))))]
    [_ (raise-syntax-error #f "parser must have the form (parser args ...)" stx)]))
  
(define (reduce-stack stack num ret-vals src-pos)
  (cond
    [(positive? num)
     (define top-frame (car stack))
     (let ([ret-vals (if src-pos
                         (cons (stack-frame-value top-frame)
                               (cons (stack-frame-start-pos top-frame)
                                     (cons (stack-frame-end-pos top-frame)
                                           ret-vals)))
                         (cons (stack-frame-value top-frame) ret-vals))])
       (reduce-stack (cdr stack) (sub1 num) ret-vals src-pos))]
    [else (values stack ret-vals)]))
  
;; extract-helper : (symbol or make-token) any any -> symbol any any any
(define (extract-helper tok v1 v2)
  (cond
    [(symbol? tok) (values tok #f v1 v2)]
    [(token? tok) (values (real-token-name tok) (real-token-value tok) v1 v2)]
    [else (raise-argument-error 'parser "(or/c symbol? token?)" 0 tok)]))

;; well-formed-position-token?: any -> boolean
;; Returns true if pt is a position token whose position-token-token
;; is itself a token or a symbol.
;; This is meant to help raise more precise error messages when
;; a tokenizer produces an erroneous position-token wrapped twice.
;; (as often happens when omitting return-without-pos).
(define (well-formed-token-field? t)
  (or (symbol? t) (token? t)))

(define (well-formed-position-token? pt)
  (and (position-token? pt) 
       (well-formed-token-field? (position-token-token pt))))

(define (well-formed-srcloc-token? st)
  (and (srcloc-token? st)
       (well-formed-token-field? (srcloc-token-token st))))
  
;; extract-src-pos : position-token -> symbol any any any
(define (extract-src-pos ip)
  (unless (well-formed-position-token? ip)
    (raise-argument-error 'parser "well-formed-position-token?" 0 ip))
  (extract-helper (position-token-token ip)
                  (position-token-start-pos ip)
                  (position-token-end-pos ip)))

(define (extract-srcloc ip)
  (unless (well-formed-srcloc-token? ip)
    (raise-argument-error 'parser "well-formed-srcloc-token?" 0 ip))
  (define loc (srcloc-token-srcloc ip))
  (extract-helper (srcloc-token-token ip)
                  (position-token (srcloc-position loc) (srcloc-line loc) (srcloc-column loc))
                  (position-token (+ (srcloc-position loc) (srcloc-span loc)) #f #f)))

  
;; extract-no-src-pos : (symbol or make-token) -> symbol any any any
(define (extract-no-src-pos ip)
  (extract-helper ip #f #f))
  
(define-struct stack-frame (state value start-pos end-pos) #:inspector (make-inspector))
  
(define (make-empty-stack i) (list (make-stack-frame i #f #f #f)))
  
  
;; The table is a vector that maps each state to a hash-table that maps a
;; terminal symbol to either an accept, shift, reduce, or goto structure.
;  We encode the structures according to the runtime-action data definition in
;; parser-actions.rkt
(define (parser-body debug? err starts ends table all-term-syms actions src-pos)
  (local ((define extract
            (if src-pos
                extract-src-pos
                extract-no-src-pos))
            
          (define (fix-error stack tok val start-pos end-pos get-token)
            (when debug? (pretty-print stack))
            (local ((define (remove-input tok val start-pos end-pos)
                      (if (memq tok ends)
                          (raise-read-error "parser: Cannot continue after error"
                                            #f #f #f #f #f)
                          (let ([a (find-action stack tok val start-pos end-pos)])
                            (cond
                              [(runtime-shift? a)
                               ;; (printf "shift:~a\n" (runtime-shift-state a))
                               (cons (make-stack-frame (runtime-shift-state a)
                                                       val
                                                       start-pos
                                                       end-pos)
                                     stack)]
                              [else
                               ;; (printf "discard input:~a\n" tok)
                               (let-values ([(tok val start-pos end-pos)
                                             (extract (get-token))])
                                 (remove-input tok val start-pos end-pos))])))))
              (let remove-states ()
                (let ([a (find-action stack 'error #f start-pos end-pos)])
                  (cond
                    [(runtime-shift? a)
                     ;; (printf "shift:~a\n" (runtime-shift-state a))
                     (set! stack 
                           (cons
                            (make-stack-frame (runtime-shift-state a) 
                                              #f 
                                              start-pos
                                              end-pos)
                            stack))
                     (remove-input tok val start-pos end-pos)]
                    [else
                     ;; (printf "discard state:~a\n" (car stack))
                     (cond
                       [(< (length stack) 2)
                        (raise-read-error "parser: Cannot continue after error"
                                          #f #f #f #f #f)]
                       [else
                        (set! stack (cdr stack))
                        (remove-states)])])))))
            
          (define (find-action stack tok val start-pos end-pos)
            (unless (hash-ref all-term-syms tok #f)
              (if src-pos
                  (err #f tok val start-pos end-pos)
                  (err #f tok val))
              (raise-read-error (format "parser: got token of unknown type ~a" tok)
                                #f #f #f #f #f))
            (hash-ref (vector-ref table (stack-frame-state (car stack))) tok #f))

          (define ((make-parser start-number) get-token)
            (unless (and (procedure? get-token)
                         (procedure-arity-includes? get-token 0))
              (error 'get-token "expected a nullary procedure, got ~e" get-token))
            (let parsing-loop ([stack (make-empty-stack start-number)]
                               [ip (get-token)])
              (let-values ([(tok val start-pos end-pos) (extract ip)])
                (let ([action (find-action stack tok val start-pos end-pos)])
                  (cond
                    [(runtime-shift? action)
                     ;; (printf "shift:~a\n" (runtime-shift-state action))
                     (parsing-loop (cons (make-stack-frame (runtime-shift-state action)
                                                           val
                                                           start-pos
                                                           end-pos)
                                         stack)
                                   (get-token))]
                    [(runtime-reduce? action)
                     ;; (printf "reduce:~a\n" (runtime-reduce-prod-num action))
                     (let-values ([(new-stack args)
                                   (reduce-stack stack 
                                                 (runtime-reduce-rhs-length action)
                                                 null
                                                 src-pos)])
                       (let ([goto 
                              (runtime-goto-state
                               (hash-ref 
                                (vector-ref table (stack-frame-state (car new-stack)))
                                (runtime-reduce-lhs action)))])
                         (parsing-loop 
                          (cons
                           (if src-pos
                               (make-stack-frame
                                goto 
                                (apply (vector-ref actions (runtime-reduce-prod-num action)) args)
                                (if (null? args) start-pos (cadr args))
                                (if (null? args) 
                                    end-pos
                                    (list-ref args (- (* (runtime-reduce-rhs-length action) 3) 1))))
                               (make-stack-frame
                                goto 
                                (apply (vector-ref actions (runtime-reduce-prod-num action)) args)
                                #f
                                #f))
                           new-stack)
                          ip)))]
                    [(runtime-accept? action)
                     ;; (printf "accept\n")
                     (stack-frame-value (car stack))]
                    [else 
                     (if src-pos
                         (err #t tok val start-pos end-pos)
                         (err #t tok val))
                     (parsing-loop (fix-error stack tok val start-pos end-pos get-token)
                                   (get-token))]))))))
    (cond
      [(null? (cdr starts)) (make-parser 0)]
      [else
       (for/list ([(l i) (in-indexed starts)])
         (make-parser i))])))