// smallobject_learner_v2.c
// Phase v11a-2: Extended Learner for multi-dimensional MID v3.5 optimization

#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <time.h>
#include "box/smallobject_learner_v2_box.h"
#include "box/smallobject_stats_mid_v3_box.h"

// ============================================================================
// Helper: Get timestamp
// ============================================================================

static inline uint64_t get_timestamp_ns(void) {
    struct timespec ts;
    clock_gettime(CLOCK_MONOTONIC, &ts);
    return (uint64_t)ts.tv_sec * 1000000000ULL + (uint64_t)ts.tv_nsec;
}

static inline uint32_t get_timestamp_ms(void) {
    return (uint32_t)(get_timestamp_ns() / 1000000ULL);
}

// ============================================================================
// Global Learner State
// ============================================================================

static SmallLearnerStatsV2 g_learner_v2_stats = {0};
static SmallLearnerClassStatsV2 g_learner_class_stats[8] = {0};

// Configuration
static uint32_t g_c5_threshold_pct = SMALL_LEARNER_C5_THRESHOLD_PCT;
static uint32_t g_eval_interval = SMALL_LEARNER_EVAL_INTERVAL;
static uint32_t g_smoothing_factor = SMALL_LEARNER_SMOOTHING_FACTOR_PCT;
static bool g_logging_enabled = false;

// ============================================================================
// Event Recording
// ============================================================================

void small_learner_v2_record_refill(uint32_t class_idx, uint64_t capacity) {
    if (class_idx >= 8) return;

    SmallLearnerStatsV2 *learn = &g_learner_v2_stats;
    SmallLearnerClassStatsV2 *cls = &g_learner_class_stats[class_idx];

    learn->allocs[class_idx] += capacity;
    learn->total_allocations += capacity;

    cls->allocs += capacity;
    cls->sample_count++;
    cls->last_update_ns = get_timestamp_ns();
}

void small_learner_v2_record_retire(uint32_t class_idx, uint32_t free_hit_ratio_bps) {
    if (class_idx >= 8) return;

    SmallLearnerStatsV2 *learn = &g_learner_v2_stats;
    SmallLearnerClassStatsV2 *cls = &g_learner_class_stats[class_idx];

    learn->retire_count[class_idx]++;
    learn->total_retires++;

    // Exponential smoothing for retire ratio
    uint32_t alpha = g_smoothing_factor;  // 0-100
    uint32_t new_val = free_hit_ratio_bps / 100;  // Convert to percentage

    if (cls->retire_ratio_smoothed == 0) {
        // First sample
        cls->retire_ratio_smoothed = new_val;
    } else {
        // EMA: smoothed = (1-alpha) * smoothed + alpha * new_val
        uint32_t smoothed = ((100 - alpha) * cls->retire_ratio_smoothed + alpha * new_val) / 100;
        cls->retire_ratio_smoothed = smoothed;
    }

    learn->retire_ratio_pct[class_idx] = cls->retire_ratio_smoothed;

    cls->sample_count++;
    cls->last_update_ns = get_timestamp_ns();
}

void small_learner_v2_record_page_stats(const SmallPageStatsMID_v3 *stat) {
    if (!stat || stat->class_idx >= 8) return;

    SmallLearnerStatsV2 *learn = &g_learner_v2_stats;
    SmallLearnerClassStatsV2 *cls = &g_learner_class_stats[stat->class_idx];

    // Record allocations
    learn->allocs[stat->class_idx] += stat->total_allocations;
    learn->total_allocations += stat->total_allocations;

    // Record retires
    learn->retire_count[stat->class_idx]++;
    learn->total_retires++;

    // Exponential smoothing for free hit ratio
    uint32_t alpha = g_smoothing_factor;
    uint32_t new_val = stat->free_hit_ratio_bps / 100;  // Convert to percentage

    if (cls->retire_ratio_smoothed == 0) {
        cls->retire_ratio_smoothed = new_val;
    } else {
        uint32_t smoothed = ((100 - alpha) * cls->retire_ratio_smoothed + alpha * new_val) / 100;
        cls->retire_ratio_smoothed = smoothed;
    }

    learn->retire_ratio_pct[stat->class_idx] = cls->retire_ratio_smoothed;

    // Update global free hit ratio (EMA)
    if (learn->free_hit_ratio_bps == 0) {
        learn->free_hit_ratio_bps = stat->free_hit_ratio_bps;
    } else {
        uint32_t smoothed = ((100 - alpha) * learn->free_hit_ratio_bps + alpha * stat->free_hit_ratio_bps) / 100;
        learn->free_hit_ratio_bps = smoothed;
    }

    // Update class stats
    cls->allocs += stat->total_allocations;
    cls->sample_count++;
    cls->last_update_ns = get_timestamp_ns();

    // Log if enabled
    if (g_logging_enabled) {
        fprintf(stderr, "[Learner_v2] C%u: allocs=%lu retire_ratio=%u%% free_hit=%u bps\n",
                stat->class_idx, stat->total_allocations,
                cls->retire_ratio_smoothed, stat->free_hit_ratio_bps);
    }
}

void small_learner_v2_ingest_stats(const SmallPageStatsAggregate_MID_v3 *agg) {
    if (!agg) return;

    SmallLearnerStatsV2 *learn = &g_learner_v2_stats;

    // Update from aggregated stats
    for (int i = 0; i < 8; i++) {
        learn->allocs[i] = agg->class_allocations[i];
        learn->retire_count[i] = agg->class_retire_count[i];

        // Update retire ratio from aggregate
        if (agg->class_retire_count[i] > 0) {
            uint32_t avg_ratio_pct = agg->class_avg_free_hit_bps[i] / 100;
            learn->retire_ratio_pct[i] = avg_ratio_pct;
            g_learner_class_stats[i].retire_ratio_smoothed = avg_ratio_pct;
        }
    }

    learn->total_allocations = agg->total_allocations;
    learn->total_retires = agg->total_pages_retired;
    learn->free_hit_ratio_bps = agg->global_avg_free_hit_bps;
    learn->sample_count = agg->eval_count;
}

// ============================================================================
// Evaluation & Decision Making
// ============================================================================

void small_learner_v2_evaluate(void) {
    SmallLearnerStatsV2 *learn = &g_learner_v2_stats;

    learn->eval_count++;
    learn->last_eval_timestamp_ms = get_timestamp_ms();

    // Calculate average page utilization
    if (learn->total_retires > 0) {
        uint64_t total_capacity = 0;
        uint64_t total_used = 0;

        for (int i = 0; i < 8; i++) {
            if (learn->retire_count[i] > 0) {
                // Estimate capacity based on retire ratio
                total_capacity += learn->allocs[i];
                total_used += (learn->allocs[i] * learn->retire_ratio_pct[i]) / 100;
            }
        }

        if (total_capacity > 0) {
            learn->avg_page_utilization = (total_used * 10000) / total_capacity;
        }
    }

    if (g_logging_enabled) {
        fprintf(stderr, "[Learner_v2] Eval #%lu: total_allocs=%lu retires=%lu util=%lu bps\n",
                learn->eval_count, learn->total_allocations,
                learn->total_retires, learn->avg_page_utilization);
    }
}

const SmallLearnerStatsV2* small_learner_v2_stats_snapshot(void) {
    return &g_learner_v2_stats;
}

const SmallLearnerClassStatsV2* small_learner_v2_class_stats(uint32_t class_idx) {
    if (class_idx >= 8) return NULL;
    return &g_learner_class_stats[class_idx];
}

// ============================================================================
// Routing Decision Support
// ============================================================================

int small_learner_v2_should_use_v7(uint32_t class_idx) {
    (void)class_idx;  // Unused in v11a-2

    // Decision based on C5 ratio
    uint32_t c5_ratio = small_learner_v2_c5_ratio_pct();

    if (c5_ratio >= g_c5_threshold_pct) {
        return 1;  // Use v7
    }

    return 0;  // Use MID_v3
}

uint32_t small_learner_v2_c5_ratio_pct(void) {
    SmallLearnerStatsV2 *learn = &g_learner_v2_stats;

    if (learn->total_allocations == 0) {
        return 0;
    }

    return (uint32_t)((learn->allocs[5] * 100) / learn->total_allocations);
}

uint32_t small_learner_v2_class_ratio_pct(uint32_t class_idx) {
    if (class_idx >= 8) return 0;

    SmallLearnerStatsV2 *learn = &g_learner_v2_stats;

    if (learn->total_allocations == 0) {
        return 0;
    }

    return (uint32_t)((learn->allocs[class_idx] * 100) / learn->total_allocations);
}

uint32_t small_learner_v2_retire_efficiency_pct(uint32_t class_idx) {
    if (class_idx >= 8) return 0;
    return g_learner_v2_stats.retire_ratio_pct[class_idx];
}

// ============================================================================
// Configuration & Control
// ============================================================================

bool small_learner_v2_enabled(void) {
    const char *env = getenv("HAKMEM_SMALL_LEARNER_V7_ENABLED");
    return (env && *env && *env != '0');
}

void small_learner_v2_set_c5_threshold_pct(uint32_t threshold) {
    g_c5_threshold_pct = threshold;
}

uint32_t small_learner_v2_get_c5_threshold_pct(void) {
    return g_c5_threshold_pct;
}

void small_learner_v2_set_eval_interval(uint32_t interval) {
    g_eval_interval = interval > 0 ? interval : SMALL_LEARNER_EVAL_INTERVAL;
}

void small_learner_v2_set_smoothing_factor(uint32_t factor_pct) {
    if (factor_pct > 100) factor_pct = 100;
    g_smoothing_factor = factor_pct;
}

void small_learner_v2_set_logging_enabled(bool enabled) {
    g_logging_enabled = enabled;
}

void small_learner_v2_reset(void) {
    memset(&g_learner_v2_stats, 0, sizeof(g_learner_v2_stats));
    memset(&g_learner_class_stats, 0, sizeof(g_learner_class_stats));
    g_c5_threshold_pct = SMALL_LEARNER_C5_THRESHOLD_PCT;
    g_eval_interval = SMALL_LEARNER_EVAL_INTERVAL;
    g_smoothing_factor = SMALL_LEARNER_SMOOTHING_FACTOR_PCT;
}

// ============================================================================
// Debugging & Monitoring
// ============================================================================

void small_learner_v2_print_stats(void) {
    const SmallLearnerStatsV2 *learn = &g_learner_v2_stats;

    fprintf(stderr, "[Learner_v2] Statistics:\n");
    fprintf(stderr, "  total_allocations=%lu total_retires=%lu\n",
            learn->total_allocations, learn->total_retires);
    fprintf(stderr, "  avg_page_util=%lu bps (%.2f%%) free_hit=%u bps\n",
            learn->avg_page_utilization, learn->avg_page_utilization / 100.0,
            learn->free_hit_ratio_bps);
    fprintf(stderr, "  eval_count=%lu sample_count=%lu\n",
            learn->eval_count, learn->sample_count);

    for (int i = 0; i < 8; i++) {
        if (learn->allocs[i] > 0) {
            fprintf(stderr, "  C%d: allocs=%lu retires=%u ratio=%u%%\n",
                    i, learn->allocs[i], learn->retire_count[i],
                    learn->retire_ratio_pct[i]);
        }
    }
}

void small_learner_v2_print_decisions(void) {
    fprintf(stderr, "[Learner_v2] Routing Decisions:\n");
    fprintf(stderr, "  C5 threshold=%u%% current_ratio=%u%%\n",
            g_c5_threshold_pct, small_learner_v2_c5_ratio_pct());

    for (uint32_t i = 5; i <= 7; i++) {
        int use_v7 = small_learner_v2_should_use_v7(i);
        fprintf(stderr, "  C%u: %s (ratio=%u%% efficiency=%u%%)\n",
                i, use_v7 ? "v7" : "MID_v3",
                small_learner_v2_class_ratio_pct(i),
                small_learner_v2_retire_efficiency_pct(i));
    }
}