// smallobject_cold_iface_mid_v3.c
// Phase v11a-2: Cold interface implementation for MID v3.5

#include <stdlib.h>
#include <stdio.h>
#include "box/smallobject_cold_iface_mid_v3_box.h"
#include "box/smallobject_stats_mid_v3_box.h"
#include "box/smallobject_mid_v35_geom_box.h"  // Phase MID-V35-HOTPATH-OPT-1: geometry SSOT
#include "box/mid_v35_hotpath_env_box.h"       // Phase MID-V35-HOTPATH-OPT-1: Step 1-3 ENV gates
#include "tiny_region_id.h"                    // For tiny_region_id_write_header

// SmallPageMeta is defined in smallobject_segment_mid_v3_box.h
#include "box/smallobject_segment_mid_v3_box.h"

// ============================================================================
// TLS Segment Management
// ============================================================================

// Thread-local segment (simplified for v11a-2)
static __thread SmallSegment_MID_v3 *tls_mid_segment = NULL;

// ============================================================================
// Helper: class_idx to slots
// ============================================================================
// Phase MID-V35-HOTPATH-OPT-1: Use geom_box as Single Source of Truth
// See: core/box/smallobject_mid_v35_geom_box.h
// (Removed local class_idx_to_slots() which had wrong C6 value: 102 instead of 128)

// ============================================================================
// Cold Interface Implementation
// ============================================================================

SmallPageMeta_MID_v3* small_cold_mid_v3_refill_page(uint32_t class_idx) {
    // Ensure TLS segment exists
    if (!tls_mid_segment) {
        tls_mid_segment = small_segment_mid_v3_create();
        if (!tls_mid_segment) {
            return NULL;
        }
    }

    // Try to take a page from the free stack
    void *page_ptr = small_segment_mid_v3_take_page(tls_mid_segment, class_idx);
    if (!page_ptr) {
        // No free pages available
        // In full implementation, would allocate new segment here
        // For v11a-2: just return NULL
        return NULL;
    }

    // Get page metadata
    SmallPageMeta_MID_v3 *page = small_segment_mid_v3_get_page_meta(
        tls_mid_segment, page_ptr
    );

    if (!page) {
        // Failed to get metadata
        return NULL;
    }

    // Initialize page for allocation
    page->class_idx = class_idx;
    page->capacity = mid_v35_slots_per_page(class_idx);
    page->alloc_count = 0;
    page->free_count = 0;

    // Phase MID-V35-HOTPATH-OPT-1 Step 1: Header prefill at refill boundary
    // When enabled, write all headers now so hot path can skip per-alloc header writes
    if (mid_v35_header_prefill_enabled()) {
        size_t slot_size = mid_v35_slot_size(class_idx);
        uint32_t cap = page->capacity;
        uint8_t *p = (uint8_t*)page_ptr;
        for (uint32_t i = 0; i < cap; i++) {
            tiny_region_id_write_header(p + i * slot_size, class_idx);
        }
    }

    return page;
}

void small_cold_mid_v3_retire_page(SmallPageMeta_MID_v3 *page) {
    if (!page || !page->segment) {
        return;
    }

    SmallSegment_MID_v3 *seg = (SmallSegment_MID_v3*)page->segment;

    // Calculate free hit ratio (in basis points, 0-10000)
    uint32_t free_hit_ratio_bps = 0;
    if (page->alloc_count > 0) {
        free_hit_ratio_bps = (page->free_count * 10000) / page->alloc_count;
    }

    // Publish stats to StatsBox
    SmallPageStatsMID_v3 stat = {
        .class_idx = page->class_idx,
        .total_allocations = page->alloc_count,
        .total_frees = page->free_count,
        .page_alloc_count = page->capacity,
        .free_hit_ratio_bps = free_hit_ratio_bps,
        .lifetime_ns = 0  // Not tracking lifetime in v11a-2
    };

    small_stats_mid_v3_publish(&stat);

    // Reset page metadata
    uint8_t old_class_idx = page->class_idx;
    page->class_idx = 0xFF;  // Mark as unassigned
    page->alloc_count = 0;
    page->free_count = 0;

    // Return page to free stack
    small_segment_mid_v3_release_page(seg, page->ptr, old_class_idx);
}