#include "gc_heap.h"
#include "../runtime.h"
#include <stdlib.h>
#include <string.h>

static RavaGCHeap_t g_heap;

void rava_gc_heap_init(void) {
    memset(&g_heap, 0, sizeof(g_heap));
    g_heap.gc_threshold = RAVA_GC_INITIAL_THRESHOLD;
    g_heap.all_blocks = NULL;
    g_heap.current_block = NULL;
    g_heap.free_blocks = NULL;
    g_heap.recyclable_blocks = NULL;
    g_heap.all_objects = NULL;
}

void rava_gc_heap_shutdown(void) {
    RavaGCBlock_t *block = g_heap.all_blocks;
    while (block) {
        RavaGCBlock_t *next = block->next;
        free(block);
        block = next;
    }

    block = g_heap.free_blocks;
    while (block) {
        RavaGCBlock_t *next = block->next;
        free(block);
        block = next;
    }

    memset(&g_heap, 0, sizeof(g_heap));
}

static RavaGCBlock_t* _rava_gc_create_block(void) {
    RavaGCBlock_t *block = calloc(1, sizeof(RavaGCBlock_t));
    if (!block) return NULL;

    block->flags = 0;
    block->free_lines = RAVA_GC_LINES_PER_BLOCK;
    memset(block->line_marks, 0, sizeof(block->line_marks));

    return block;
}

bool rava_gc_request_block(void) {
    if (g_heap.free_blocks) {
        RavaGCBlock_t *block = g_heap.free_blocks;
        g_heap.free_blocks = block->next;

        block->next = g_heap.all_blocks;
        block->prev = NULL;
        if (g_heap.all_blocks) {
            g_heap.all_blocks->prev = block;
        }
        g_heap.all_blocks = block;

        g_heap.current_block = block;
        g_heap.bump_ptr = block->data;
        g_heap.block_limit = block->data + RAVA_GC_BLOCK_SIZE;
        return true;
    }

    if (g_heap.recyclable_blocks) {
        RavaGCBlock_t *block = g_heap.recyclable_blocks;
        g_heap.recyclable_blocks = block->next;

        block->next = g_heap.all_blocks;
        block->prev = NULL;
        if (g_heap.all_blocks) {
            g_heap.all_blocks->prev = block;
        }
        g_heap.all_blocks = block;

        g_heap.current_block = block;
        g_heap.bump_ptr = block->data;
        g_heap.block_limit = block->data + RAVA_GC_BLOCK_SIZE;
        return true;
    }

    RavaGCBlock_t *block = _rava_gc_create_block();
    if (!block) return false;

    block->next = g_heap.all_blocks;
    block->prev = NULL;
    if (g_heap.all_blocks) {
        g_heap.all_blocks->prev = block;
    }
    g_heap.all_blocks = block;

    g_heap.current_block = block;
    g_heap.bump_ptr = block->data;
    g_heap.block_limit = block->data + RAVA_GC_BLOCK_SIZE;

    return true;
}

void* rava_gc_heap_alloc(size_t size, uint8_t type) {
    size = RAVA_ALIGN(size, 8);

    if (size > RAVA_GC_BLOCK_SIZE) {
        RavaGCHeader_t *obj = calloc(1, size);
        if (!obj) return NULL;

        obj->gc_type = type;
        obj->gc_mark = RAVA_GC_WHITE;
        obj->gc_age = 0;
        obj->gc_flags = RAVA_GC_FLAG_PINNED;
        obj->gc_size = (uint32_t)size;

        obj->gc_next = g_heap.all_objects;
        g_heap.all_objects = obj;

        g_heap.total_allocated += size;
        return obj;
    }

    if (!g_heap.current_block || g_heap.bump_ptr + size > g_heap.block_limit) {
        if (!rava_gc_request_block()) {
            return NULL;
        }
    }

    RavaGCHeader_t *obj = (RavaGCHeader_t*)g_heap.bump_ptr;
    g_heap.bump_ptr += size;
    g_heap.total_allocated += size;

    obj->gc_type = type;
    obj->gc_mark = RAVA_GC_WHITE;
    obj->gc_age = 0;
    obj->gc_flags = 0;
    obj->gc_size = (uint32_t)size;

    obj->gc_next = g_heap.all_objects;
    g_heap.all_objects = obj;

    return obj;
}

void rava_gc_heap_free(void *ptr, size_t size) {
    (void)ptr;
    (void)size;
}

void rava_gc_recycle_blocks(void) {
    RavaGCBlock_t *block = g_heap.all_blocks;
    RavaGCBlock_t *prev = NULL;

    while (block) {
        RavaGCBlock_t *next = block->next;

        bool has_live = false;
        for (size_t i = 0; i < RAVA_GC_LINES_PER_BLOCK; i++) {
            if (block->line_marks[i]) {
                has_live = true;
                break;
            }
        }

        if (!has_live && block != g_heap.current_block) {
            if (prev) {
                prev->next = next;
            } else {
                g_heap.all_blocks = next;
            }
            if (next) {
                next->prev = prev;
            }

            block->next = g_heap.free_blocks;
            block->prev = NULL;
            g_heap.free_blocks = block;

            memset(block->line_marks, 0, sizeof(block->line_marks));
            block->flags = 0;
            block->free_lines = RAVA_GC_LINES_PER_BLOCK;
        } else {
            prev = block;
        }

        block = next;
    }
}

RavaGCHeap_t* rava_gc_get_heap(void) {
    return &g_heap;
}