/**
 *  environment/function_bindings.c
 *
 *  Post Scarcity Software Environment:
 *
 *  Provide bindings for substrate functions. At least in theory, these
 *  bindings only need to be initialised on node zero.
 *  todo: they really ought to be in a namespace ::system:bootstrap, once I
 *  have namespaces and paths working.
 *
 *  (c) 2026 Simon Brooke <simon@journeyman.cc>
 *  Licensed under GPL version 2.0, or, at your option, any later version.
 */

#include <stdbool.h>
#include <stdlib.h>
#include <wchar.h>

#include "debug.h"
#include "environment/privileged_keywords.h"

#include "io/io.h"
#include "io/peek.h"
#include "io/print.h"
#include "io/read.h"

#include "memory/node.h"
#include "memory/pointer.h"
#include "memory/tags.h"

#include "ops/assoc.h"
#include "ops/bind.h"
#include "ops/cond.h"
#include "ops/eq.h"
#include "ops/eval_apply.h"
#include "ops/inspect.h"
#include "ops/keys.h"
#include "ops/list_ops.h"
#include "ops/mapcar.h"
#include "ops/progn.h"
#include "ops/quote.h"
#include "ops/repl.h"
#include "ops/reverse.h"
#include "payloads/stack.h"
#include "ops/string_ops.h"
#include "ops/truth.h"

#include "payloads/cons.h"
#include "payloads/function.h"
#include "payloads/special.h"
#include "payloads/stack.h"

/**
 * Bind this compiled `executable` function, as a Lisp function, to
 * this name in the `oblist`.
 * \todo where a function is not compiled from source, we could cache
 * the name on the source pointer. Would make stack frames potentially
 * more readable and aid debugging generally.
 */

struct pso_pointer
bind_function( struct pso_pointer frame_pointer, wchar_t *name, wchar_t *doc,
               struct pso_pointer ( *executable ) ( struct pso_pointer ) ) {
    struct pso_pointer result = fetch_env( frame_pointer );
    struct pso_pointer n = c_string_to_lisp_symbol( frame_pointer, name );
    struct pso_pointer d = c_string_to_lisp_string( frame_pointer, doc );

    struct pso_pointer meta = make_cons( frame_pointer,
                                         make_cons( frame_pointer,
                                                    privileged_keyword_layer,
                                                    privileged_keyword_bootstrap ),
                                         make_cons( frame_pointer,
                                                    make_cons( frame_pointer,
                                                               privileged_keyword_name,
                                                               n ),
                                                    make_cons( frame_pointer,
                                                               make_cons
                                                               ( frame_pointer,
                                                                 privileged_keyword_documentation,
                                                                 d ),
                                                               nil ) ) );

    struct pso_pointer r = make_function( frame_pointer, meta, executable );

    debug_print( doc, DEBUG_BOOTSTRAP, 0 );
    if ( !exceptionp( r ) ) {
        debug_print( L"... bound\n", DEBUG_BOOTSTRAP, 0 );
        result =
            make_cons( frame_pointer, make_cons( frame_pointer, n, r ),
                       result );
    } else {
        debug_print( L"... failed to bind\n", DEBUG_BOOTSTRAP, 0 );
    }

    return result;
}

/**
 * Bind this compiled `executable` function, as a Lisp special form, to
 * this `name` in the `oblist`.
 */
struct pso_pointer
bind_special( struct pso_pointer frame_pointer, wchar_t *name, wchar_t *doc,
              struct pso_pointer ( *executable ) ( struct pso_pointer ) ) {
    struct pso_pointer result = fetch_env( frame_pointer );
    struct pso_pointer n = c_string_to_lisp_symbol( frame_pointer, name );
    struct pso_pointer d = c_string_to_lisp_string( frame_pointer, doc );

    struct pso_pointer meta = make_cons( frame_pointer,
                                         make_cons( frame_pointer,
                                                    privileged_keyword_bootstrap,
                                                    nil ),
                                         make_cons( frame_pointer,
                                                    make_cons( frame_pointer,
                                                               privileged_keyword_name,
                                                               n ),
                                                    make_cons( frame_pointer,
                                                               make_cons
                                                               ( frame_pointer,
                                                                 privileged_keyword_documentation,
                                                                 d ),
                                                               nil ) ) );

    struct pso_pointer r = make_special( frame_pointer, meta, executable );

    debug_print( doc, DEBUG_BOOTSTRAP, 0 );
    if ( !exceptionp( r ) ) {
        debug_print( L"... bound\n", DEBUG_BOOTSTRAP, 0 );
        result =
            make_cons( frame_pointer, make_cons( frame_pointer, n, r ),
                       result );
    } else {
        debug_print( L"... failed to bind\n", DEBUG_BOOTSTRAP, 0 );
    }

    return result;
}

struct function_data {
    wchar_t *name;
    wchar_t *documentation;
    void *executable;
};

/* right, the problem with all those pretty '#ifdefs' which might allow us to
 * simply switch functions on and off just by including or not including .h
 * files is that the C compiler is too primitive to know how many items there
 * are in an array. So this number must be edited manually, and must be right.
 */
#define N_FUNCTION_INITIALISERS 4

/** initialisers for functions */
struct function_data function_initialisers[] = {
#ifdef _psse_io_io_h
    {L"close", L"(close stream): close `stream`.", &lisp_close},
    {L"open",
     L"(open stream), (open stream write?): open `stream`; if `write?` is "
     L"present and is non-nil, open for writing, else for reading.",
     &lisp_open},
    {L"slurp",
     L"(slurp stream): read the whole contents of this `stream`, "
     L"which may "
     L"be an open stream open for reading or a URL, into a string, and return "
     L"the " L"string.",
     &lisp_slurp},
#endif
#ifdef __psse_io_peek_h
    {L"peek",
     L"(peek stream): return the next character which may be read from "
     L"`stream`, without removing it.",
     &peek},
#endif
#ifdef __psse_io_print_h
    {L"print",
     L"(print object), (print object stream) print this `object` in a format "
     L"suitable to be read by `read`, q.v.; if `stream` is specified and is a "
     L"stream open for writing, to that stream.",
     &print},
    {L"princ",
     L"(princ object), (princ object stream) print this `object` in a format "
     L"more suited to human readers; if `stream` is specified and is a stream "
     L"open for writing, to that stream.",
     &print},
#endif
#ifdef __psse_io_read_h
    {L"read",
     L"(read stream) read one complete Lisp expression from `stream`, and "
     L"return that expression unevaluated.",
     &read},
    {L"read-character",
     L"(read-character stream): read a single character from `stream` and "
     L"return it.",
     &read_character},
    {L"read-number",
     L"(read-number stream): read a number from `stream` and return it.",
     &read_number},
    {L"read-symbol",
     L"(read-symbol stream): read a symbol from `stream` and return it.",
     &read_symbol},
#endif
#ifdef __psse_ops_assoc_h
    {L"assoc",
     L"(assoc key store): search `store` for the value associated with "
     L"`key`.",
     &assoc},
#endif
#ifdef __psse_ops_bind_h
    {L"bind!",
     L"(bind! key value store): bind `key` to `value` in this store, modifying "
     L"the store if it is writable to the user, otherwise returning a new "
     L"store",
     &bind},
#endif
#ifdef __psse_ops_eq_h
    {L"eq",
     L"(eq args...): shallow, cheap equality; returns `t` if all `args...` "
     L"are the same object, else `nil`.",
     &eq},
    {L"equal",
     L"(equal a b): expensive, deep equality: returns `t` if objects `a` "
     L"and `b` have recursively equal value.",
     &equal},
#endif
#ifdef __psse_ops_eval_apply_h
    // TODO: there's a lot of other stuff in eval_apply.c, which ought to be in
    // other files but at present isn't.
    {L"apply",
     L"(apply fn args...): apply this `fn` to these `args...` and return "
     L"their value.",
     &lisp_apply},
    {L"eval",
     L"(eval expression): evaluate this `expression` and return its value",
     &lisp_eval},
#endif
#ifdef __psse_ops_inspect_h
    {L"inspect",
     L"(inspect expr), (inspect expr write-stream): inspect one complete "
     L"lisp expression and return `nil`. If `write-stream` is specified and "
     L"is a write stream, then print to that stream, else to the stream "
     L"which is the value of `*out*` in the environment.",
     &lisp_inspect},
#endif
#ifdef __psse_ops_keys_h
    {L"keys", L"(keys store): returns a list of the keys in this `store`.",
     &lisp_keys},
#endif
#ifdef __psse_ops_list_ops_h
    {L"count",
     L"(count sequence): returns the number of top level elements in "
     L"`sequence`.",
     &count},
#endif
#ifdef __psse_ops_mapcar_h
    {L"mapcar",
     L"(mapcar fn list): map this `fn` over this `list`, and return a list "
     L"of the results.",
     &lisp_mapcar},
#endif
#ifdef __psse_ops_progn_h
    {L"progn",
     L"(progn expressions...): Evaluate each expression in "
     L"`expressions` in turn and return the value of the last.",
     &lisp_progn},
#endif
#ifdef __psse_ops_repl_h
    {L"repl", L"(repl show_prompt?): Start a new read, eval, print loop.",
     &repl},
#endif
#ifdef __psse_ops_reverse_h
    {L"reverse",
     L"(reverse sequence): return a sequence like this `sequence`, but with "
     L"the order of top level elements reversed.",
     &reverse},
#endif
#ifdef __psse_ops_truth_h
    {L"and",
     L"(and expressions...): returns `t` if none of these `expressions...` "
     L"evaluates to `nil`, else `nil`.",
     &and},
    {L"nil?",
     L"(nil? expression): returns `t` if `expression` evaluates to `nil`, else "
     L"`nil`.",
     &nilp},
    {L"not",
     L"(not expression): returns `t` unless `expression` evaluates to `nil`, "
     L"else " L"`nil`.",
     &not},
    {L"or",
     L"(or expressions...): returns `nil` if every one of these `expressions...` "
     L"evaluates to `nil`, else `t`.",
     &or},
    {L"true?",
     L"(true? expression): returns `t` if `expression` evaluates to `t`, else "
     L"`nil`.",
     &truep},
#endif

    {L"END MARKER", L"END MARKER", NULL}
};

/* right, the problem with all those pretty '#ifdefs' which might allow us to
 * simply switch functions on and off just by including or not including .h
 * files is that the C compiler is too primitive to know how many items there
 * are in an array */
#define N_SPECIAL_INITIALISERS 1

/** initialisers for special forms */
struct function_data special_initialisers[] = {
#ifdef __psse_ops_cond_h
    {L"cond",
     L"(cond clauses...): special form; conditional. Each `clause` is expected "
     L"to be a "
     L"list; if the first item in such a list evaluates to non-nil, the "
     L"remaining items in that list are evaluated in turn and the value of "
     L"the last returned. If no arg `clause` has a first element which "
     L"evaluates to non nil, then nil is returned",
     &lisp_cond},
#endif
#ifdef __psse_ops_quote_h
    {L"quote",
     L"(quote expression): special form; protect `expression` from "
     L"evaluation.",
     &quote},
#endif
    {L"END MARKER", L"END MARKER", NULL}
};

struct pso_pointer
initialise_function_bindings( struct pso_pointer frame_pointer ) {
    struct pso_pointer result = fetch_env( frame_pointer );

    for ( int i = 0; function_initialisers[i].executable != NULL; i++ ) {
        struct pso_pointer b = c_car( bind_function( frame_pointer,
                                                     function_initialisers
                                                     [i].name,
                                                     function_initialisers
                                                     [i].documentation,
                                                     function_initialisers
                                                     [i].executable ) );
        result = make_cons( frame_pointer, b, result );
    }
    for ( int i = 0; special_initialisers[i].executable != NULL; i++ ) {
        struct pso_pointer b = c_car( bind_special( frame_pointer,
                                                    special_initialisers
                                                    [i].name,
                                                    special_initialisers
                                                    [i].documentation,
                                                    special_initialisers
                                                    [i].executable ) );
        result = make_cons( frame_pointer, b, result );
    }

    return result;
}