/*
 * kernel.c – Kernel entry point and interactive shell loop.
 *
 * kmain() is called by the UEFI loader (main.c) after the ELF kernel
 * has been mapped into memory.  It initialises subsystems (IDT, memory,
 * tasks), prints a welcome banner, and enters an interactive read-
 * eval-print loop that dispatches typed commands via commands.c.
 *
 * While waiting for keyboard input, the shell yields to the cooperative
 * scheduler so that background tasks can make progress.
 */

#include <efi.h>

#include "boot_info.h"
#include "commands.h"
#include "idt.h"
#include "memory.h"
#include "task.h"

/* Null-safe print helper used throughout the kernel. */
#define SAFE_PRINT(Boot, ...)                           \
    do {                                                \
        if ((Boot) != NULL && (Boot)->print != NULL) {  \
            (Boot)->print(__VA_ARGS__);                 \
        }                                               \
    } while (0)

/* ================================================================
 *  Kernel entry point
 * ================================================================ */

void kmain(BootInfo *Boot)
{
    EFI_INPUT_KEY Key;
    EFI_STATUS Status;
    UINTN read_errors = 0;

    if (Boot == NULL) {
        return;
    }

    if (Boot->clear_screen != NULL) {
        Status = Boot->clear_screen();
        if (EFI_ERROR(Status)) {
            SAFE_PRINT(Boot, L"clear_screen failed: %r\n\r", Status);
        }
    }

    if (Boot->set_attribute != NULL) {
        Status = Boot->set_attribute(EFI_TEXT_ATTR(EFI_LIGHTGREEN, EFI_BLACK));
        if (EFI_ERROR(Status)) {
            SAFE_PRINT(Boot, L"set_attribute failed: %r\n\r", Status);
        }
    }

    /* ---- Subsystem initialisation ---- */
    idt_init(Boot);
    memory_init(Boot);
    task_init(Boot);

    /* ---- Welcome banner ---- */
    SAFE_PRINT(Boot, L"  Welcome to Simple UEFI Operating System!\n\r");
    SAFE_PRINT(Boot, L"================================================\n\r");
    SAFE_PRINT(Boot, L"\n\r");
    SAFE_PRINT(Boot, L"System Information:\n\r");
    if (Boot->SystemTable != NULL) {
        SAFE_PRINT(Boot, L"  UEFI Firmware Vendor: %s\n\r",
                   Boot->SystemTable->FirmwareVendor);
        SAFE_PRINT(Boot, L"  UEFI Firmware Revision: %d.%d\n\r",
                   Boot->SystemTable->FirmwareRevision >> 16,
                   Boot->SystemTable->FirmwareRevision & 0xFFFF);
    } else {
        SAFE_PRINT(Boot, L"  UEFI System Table: Unavailable\n\r");
    }
    SAFE_PRINT(Boot, L"\n\r");

    SAFE_PRINT(Boot, L"Available Services:\n\r");
    SAFE_PRINT(Boot, L"  - Console Input/Output: %s\n\r",
               (Boot->read_key != NULL && Boot->print != NULL) ? L"Active" : L"Unavailable");
    SAFE_PRINT(Boot, L"  - Runtime Services: %s\n\r",
               (Boot->SystemTable != NULL &&
                Boot->SystemTable->RuntimeServices != NULL) ? L"Active" : L"Unavailable");
    SAFE_PRINT(Boot, L"  - Boot Services: %s\n\r",
               (Boot->SystemTable != NULL &&
                Boot->SystemTable->BootServices != NULL) ? L"Active" : L"Unavailable");
    SAFE_PRINT(Boot, L"\n\r");
    SAFE_PRINT(Boot, L"Type 'help' for a list of commands.\n\r\n\r");

    /* ---- Interactive shell loop ---- */
    CHAR16 line[128];
    UINTN len = 0;

    SAFE_PRINT(Boot, L"-> ");

    while (TRUE) {
        /* Try non-blocking read first; yield to other tasks while idle */
        if (Boot->try_read_key != NULL) {
            Status = Boot->try_read_key(&Key);
            if (Status == EFI_NOT_READY) {
                task_yield();
                continue;
            }
        } else if (Boot->read_key != NULL) {
            Status = Boot->read_key(&Key);
        } else {
            SAFE_PRINT(Boot, L"Console input unavailable.\n\r");
            break;
        }

        if (EFI_ERROR(Status)) {
            read_errors++;
            if (read_errors == 1 || (read_errors % 64) == 0) {
                SAFE_PRINT(Boot, L"read_key failed: %r\n\r", Status);
            }
            continue;
        }
        read_errors = 0;

        if (Key.UnicodeChar == L'\r' || Key.UnicodeChar == L'\n') {
            /* Enter pressed: execute the buffered command */
            line[len] = L'\0';
            SAFE_PRINT(Boot, L"\n\r");
            execute_command(Boot, line);

            /* Reset for next command */
            len = 0;
            SAFE_PRINT(Boot, L"-> ");
        } else if (Key.ScanCode == 0x08 || Key.UnicodeChar == L'\b' || Key.UnicodeChar == 0x7F) {
            /* Backspace */
            if (len > 0) {
                len--;
                SAFE_PRINT(Boot, L"\b \b");
            }
        } else if (Key.UnicodeChar >= 32 && Key.UnicodeChar < 127) {
            /* Printable ASCII */
            if (len < (sizeof(line) / sizeof(line[0]) - 1)) {
                line[len++] = Key.UnicodeChar;
                SAFE_PRINT(Boot, L"%c", Key.UnicodeChar);
            }
        }
    }
}