#include <idt.h>
#include <common.h>
#include <string_utils.h>
#include <pic.h>
#include <serial.h>

// Defined in isr.S — 256 ISR stubs
extern "C" void* isr_stub_table[256];

static idt_entry g_idt[256];
static idt_ptr   g_idt_ptr;
static isr_handler_t g_handlers[256] = {0};

void idt_set_handler(UINT8 vector, isr_handler_t handler) {
    g_handlers[vector] = handler;
}

// Called from isr.S common handler
extern "C" void isr_dispatch(trap_frame* frame) {
    UINT8 vector = (UINT8)frame->vector;

    if (g_handlers[vector]) {
        g_handlers[vector](frame);
    } else if (vector < 32) {
        serial_write("IDT: unhandled exception #");
        serial_write_hex(vector);
        serial_write(" error=");
        serial_write_hex(frame->error_code);
        serial_write("\n");
        while (1) ASM("hlt");
    }
}

// IDT helpers (defined in idt_helpers.S)
extern "C" void idt_load(UINT64 base, UINT16 limit);

static void idt_set_entry(UINT8 vector, UINT64 handler_addr) {
    g_idt[vector].offset_low  = handler_addr & 0xFFFF;
    g_idt[vector].selector    = 0x08;  // kernel code segment
    g_idt[vector].ist         = 0;
    g_idt[vector].type_attr   = 0x8E;  // present, DPL=0, 64-bit interrupt gate
    g_idt[vector].offset_mid  = (handler_addr >> 16) & 0xFFFF;
    g_idt[vector].offset_high = (handler_addr >> 32) & 0xFFFFFFFF;
    g_idt[vector].reserved    = 0;
}

void idt_init(void) {
    serial_write("IDT: initializing 256 entries\n");

    // Clear IDT
    for (SSINT32 i = 0; i < 256; i++) {
        g_idt[i] = {0};
        g_handlers[i] = NULL;
    }

    // Install all 256 ISR stubs
    for (SSINT32 i = 0; i < 256; i++) {
        idt_set_entry(i, (UINT64)isr_stub_table[i]);
    }

    // Load IDT
    g_idt_ptr.limit = sizeof(g_idt) - 1;
    g_idt_ptr.base = (UINT64)&g_idt[0];
    idt_load(g_idt_ptr.base, g_idt_ptr.limit);

    serial_write("IDT: loaded\n");
}