/**
 *  environment/environment.c
 *
 *  Initialise a MINIMAL environment.
 *
 *  (c) 2026 Simon Brooke <simon@journeyman.cc>
 *  Licensed under GPL version 2.0, or, at your option, any later version.
 */

#include <stdbool.h>

#include "debug.h"

#include "environment/function_bindings.h"
#include "environment/privileged_keywords.h"
#include "memory/memory.h"
#include "memory/node.h"
#include "memory/pointer.h"
#include "memory/pso.h"
#include "memory/pso2.h"
#include "memory/tags.h"

#include "ops/bind.h"
#include "ops/string_ops.h"

#include "payloads/psse_string.h"

#include "ops/stack_ops.h"
#include "ops/truth.h"
#include "payloads/stack.h"

/**
 * @brief Flag to prevent re-initialisation.
 */
bool environment_initialised = false;

/**
 * @brief Initialise a minimal environment, so that Lisp can be bootstrapped.
 * 
 * @param node the index of the node we are initialising.
 * @return a proto-environment on success, else an exception.
 */

struct pso_pointer initialise_environment( uint32_t node ) {
    struct pso_pointer result = initialise_memory( node );
    struct pso_pointer frame_pointer = nil; // can't have a frame pointer before we've initialised nil and t

    if ( c_truep( result ) ) {
        debug_print( U"Initialising `nil`... ", DEBUG_BOOTSTRAP, 0 );
        struct pso_pointer n = allocate( frame_pointer, NILTAG, 2 );

        if ( ( n.page == 0 ) && ( n.offset == 0 ) ) {
            struct pso2 *object = pointer_to_object( n );
            object->payload.cons.car = nil;
            object->payload.cons.cdr = nil;

            nil = n;
            lock_object( nil );
            debug_print( U"success\n", DEBUG_BOOTSTRAP, 0 );
        } else {
            result = nil;
            debug_print( U"fail\n", DEBUG_BOOTSTRAP, 0 );
        }
    }
    if ( !c_nilp( result ) ) {
        debug_print( U"Initialising `t`... ", DEBUG_BOOTSTRAP, 0 );
        struct pso_pointer n = allocate( frame_pointer, TRUETAG, 2 );

        // offset is in words, and size of a pso2 is four words
        if ( ( n.page == 0 ) && ( n.offset == 4 ) ) {
            struct pso2 *object = pointer_to_object( n );
            object->payload.string.character = L't';
            object->payload.cons.cdr = t;

            t = n;
            lock_object( t );
            debug_print( U"success\n", DEBUG_BOOTSTRAP, 0 );
        } else {
            result = nil;
            debug_print( U"fail\n", DEBUG_BOOTSTRAP, 0 );
        }
    }
    if ( !exceptionp( result ) ) {
        result =
            lisp_bind( make_frame
                       ( 3, frame_pointer,
                         c_string_to_lisp_symbol( frame_pointer, U"niU" ), nil,
                         nil ) );
        debug_print( U"Environment after binding `nil`: ", DEBUG_BOOTSTRAP,
                     0 );
        debug_print_object( result, DEBUG_BOOTSTRAP, 0 );
        result =
            lisp_bind( make_frame
                       ( 3, frame_pointer,
                         c_string_to_lisp_symbol( frame_pointer, U"t" ), t,
                         result ) );

        environment_initialised = true;
        debug_print( U"Environment after binding `t`: ", DEBUG_BOOTSTRAP, 0 );
        debug_print_object( result, DEBUG_BOOTSTRAP, 0 );

        debug_print( U"\nEnvironment initialised successfully.\n",
                     DEBUG_BOOTSTRAP, 0 );
	}

	initialise_privileged_keywords(frame_pointer);

	result = initialise_function_bindings(push_local(
		frame_pointer, make_frame_with_env(0, frame_pointer, result)));

	dec_ref(frame_pointer);

	return result;
}