#include "alloc.h"
#include "allocArea.h"
#include "ata.h"
#include "exception.h"
#include "gdt.h"
#include "idt.h"
#include "interrupt.h"
#include "io.h"
#include "irq.h"
#include "kernel.h"
#include "keyboard.h"
#include "klibc.h"
#include "mem.h"
#include "mmuContext.h"
#include "multiboot.h"
#include "paging.h"
#include "pit.h"
#include "process.h"
#include "serial.h"
#include "stack.h"
#include "stdarg.h"
#include "swintr.h"
#include "thread.h"
#ifdef RUN_TEST
#include "test.h"
#endif
#include "time.h"
#include "types.h"
#include "vga.h"

#define CHECK_FLAG(flags, bit) ((flags) & (1 << (bit)))

void idleThread(void *arg)
{
    (void)arg;
    while (1) {
        VGAPrintf(GREEN, BLACK, 0, VGA_HEIGHT - 1, "%d", (jiffies / HZ));
        threadYield();
    }
}

/**
 * Make sure the program is in a valid ELF format, map it into memory,
 * and return the address of its entry point (ie _start function)
 *
 * @return 0 when the program is not a valid ELF
 */
static uaddr_t loadElfProg(const char *prog)
{
    int i;

    /**
     * Typedefs, constants and structure definitions as given by the ELF
     * standard specifications.
     */
    typedef unsigned long Elf32_Addr;
    typedef unsigned long Elf32_Word;
    typedef unsigned short Elf32_Half;
    typedef unsigned long Elf32_Off;
    // typedef signed long Elf32_Sword;

    /* Elf identification */

#define EI_NIDENT 16
    typedef struct {
        unsigned char e_ident[EI_NIDENT];
        Elf32_Half e_type;
        Elf32_Half e_machine;
        Elf32_Word e_version;
        Elf32_Addr e_entry;
        Elf32_Off e_phoff;
        Elf32_Off e_shoff;
        Elf32_Word e_flags;
        Elf32_Half e_ehsize;
        Elf32_Half e_phentsize;
        Elf32_Half e_phnum;
        Elf32_Half e_shentsize;
        Elf32_Half e_shnum;
        Elf32_Half e_shstrndx;
    } __attribute__((packed)) Elf32_Ehdr_t;

/* e_ident value */
#define ELFMAG0 0x7f
#define ELFMAG1 'E'
#define ELFMAG2 'L'
#define ELFMAG3 'F'

/* e_ident offsets */
#define EI_MAG0 0
#define EI_MAG1 1
#define EI_MAG2 2
#define EI_MAG3 3
#define EI_CLASS 4
#define EI_DATA 5
#define EI_VERSION 6
#define EI_PAD 7

/* e_ident[EI_CLASS] */
#define ELFCLASSNONE 0
#define ELFCLASS32 1
#define ELFCLASS64 2

/* e_ident[EI_DATA] */
#define ELFDATANONE 0
#define ELFDATA2LSB 1
#define ELFDATA2MSB 2

/* e_type */
#define ET_NONE 0        /* No file type       */
#define ET_REL 1         /* Relocatable file   */
#define ET_EXEC 2        /* Executable file    */
#define ET_DYN 3         /* Shared object file */
#define ET_CORE 4        /* Core file          */
#define ET_LOPROC 0xff00 /* Processor-specific */
#define ET_HIPROC 0xffff /* Processor-specific */

/* e_machine */
#define EM_NONE 0  /* No machine     */
#define EM_M32 1   /* AT&T WE 32100  */
#define EM_SPARC 2 /* SPARC          */
#define EM_386 3   /* Intel 80386    */
#define EM_68K 4   /* Motorola 68000 */
#define EM_88K 5   /* Motorola 88000 */
#define EM_860 7   /* Intel 80860    */
#define EM_MIPS 8  /* MIPS RS3000    */

/* e_version */
#define EV_NONE 0    /* invalid version */
#define EV_CURRENT 1 /* current version */

    typedef struct {
        Elf32_Word p_type;
        Elf32_Off p_offset;
        Elf32_Addr p_vaddr;
        Elf32_Addr p_paddr;
        Elf32_Word p_filesz;
        Elf32_Word p_memsz;
        Elf32_Word p_flags;
        Elf32_Word p_align;
    } __attribute__((packed)) Elf32_Phdr_t;

/* Reserved segment types p_type */
#define PT_NULL 0
#define PT_LOAD 1
#define PT_DYNAMIC 2
#define PT_INTERP 3
#define PT_NOTE 4
#define PT_SHLIB 5
#define PT_PHDR 6
#define PT_LOPROC 0x70000000
#define PT_HIPROC 0x7fffffff

/* p_flags */
#define PF_X 1
#define PF_W 2
#define PF_R 4

    Elf32_Ehdr_t *elf_hdr = (Elf32_Ehdr_t *)prog;
    Elf32_Phdr_t *elf_phdrs;

    /* Macro to check expected values for some fields in the ELF header */
#define ELF_CHECK(hdr, field, expected_value)                                                 \
    ({                                                                                        \
        if ((hdr)->field != (expected_value)) {                                               \
            printf("ELF prog : for %s, expected %x, got %x\n", #field,                        \
                   (unsigned)(expected_value), (unsigned)(hdr)->field);                       \
            return 0;                                                                         \
        }                                                                                     \
    })

    ELF_CHECK(elf_hdr, e_ident[EI_MAG0], ELFMAG0);
    ELF_CHECK(elf_hdr, e_ident[EI_MAG1], ELFMAG1);
    ELF_CHECK(elf_hdr, e_ident[EI_MAG2], ELFMAG2);
    ELF_CHECK(elf_hdr, e_ident[EI_MAG3], ELFMAG3);
    ELF_CHECK(elf_hdr, e_ident[EI_CLASS], ELFCLASS32);
    ELF_CHECK(elf_hdr, e_ident[EI_DATA], ELFDATA2LSB);
    ELF_CHECK(elf_hdr, e_type, ET_EXEC);
    ELF_CHECK(elf_hdr, e_version, EV_CURRENT);

    /* Get the begining of the program header table */
    elf_phdrs = (Elf32_Phdr_t *)(prog + elf_hdr->e_phoff);

    /* Map the program segment in R/W mode. To make things clean, we
       should iterate over the sections, not the program header */
    for (i = 0; i < elf_hdr->e_phnum; i++) {
        uaddr_t uaddr;

        /* Ignore the empty program headers that are not marked "LOAD" */
        if (elf_phdrs[i].p_type != PT_LOAD) {
            continue;
        }

        if (elf_phdrs[i].p_vaddr < PAGING_BASE_USER_ADDRESS) {
            printf("User program has an incorrect address 0x%x\n", elf_phdrs[i].p_vaddr);
            return (uaddr_t)NULL;
        }

        /* Map pages of physical memory into user space */
        for (uaddr = ALIGN_DOWN(elf_phdrs[i].p_vaddr, PAGE_SIZE);
             uaddr < elf_phdrs[i].p_vaddr + elf_phdrs[i].p_memsz; uaddr += PAGE_SIZE) {
            paddr_t ppage;
            ppage = allocPhyPage(1);

            printf("map user page at 0x%x\n", uaddr);
            assert(pageMap(uaddr, ppage,
                           PAGING_MEM_USER | PAGING_MEM_WRITE | PAGING_MEM_READ) == 0);

            unrefPhyPage(ppage);
        }

        printf("memcpy at 0x%x from file offset %d size %d\n", elf_phdrs[i].p_vaddr, elf_phdrs[i].p_offset, elf_phdrs[i].p_filesz);
        /* Copy segment into memory */
        memcpy((void *)elf_phdrs[i].p_vaddr, (void *)(prog + elf_phdrs[i].p_offset),
               elf_phdrs[i].p_filesz);
    }

    return elf_hdr->e_entry;
}

void loadUserSpace()
{
    struct ata_partition *part = ATAGetPartition(0);

    if (part == NULL) {
        printf("No user partition found\n");
        return;
    }

    char *buf = malloc(26 * 512);
    if (buf == NULL) {
        printf("ENOMEM\n");
        return;
    }

    if (ATAReadPartitionSector(part, 0, 26, buf)) {
        printf("Fail to read from disk\n");
        return;
    }

    struct process *proc = processCreate("UserSpace");

    threadChangeCurrentContext(processGetMMUContext(proc));
    uaddr_t prog = loadElfProg(buf);
    if (prog == (uaddr_t)NULL) {
        free(buf);
        return;
    }

    // Alloc user stack
    uaddr_t stackTop    = 0xfffffffc;
    uaddr_t stackBottom = ALIGN_DOWN(stackTop, PAGE_SIZE);
    paddr_t stackPhy    = allocPhyPage(1);
    assert(pageMap(stackBottom, stackPhy,
                   PAGING_MEM_USER | PAGING_MEM_WRITE | PAGING_MEM_READ) == 0);
    unrefPhyPage(stackPhy);

    threadCreateUser("UserProg", proc, prog, 0, 0, stackTop);
    processUnref(proc);
    threadChangeCurrentContext(NULL);

    free(buf);
}

// Multiboot information available here :
// https://www.gnu.org/software/grub/manual/multiboot/multiboot.html#kernel_002ec
// https://www.gnu.org/software/grub/manual/multiboot/html_node/Boot-information-format.html#Boot%20information%20format
void kmain(unsigned long magic, unsigned long addr)
{
    unsigned long upperMemKB = 0;
    int memMapAvailable      = 0;
    paddr_t lastUsedByMem;
    paddr_t firstUsedByMem;

    VGASetup(BLACK, GREEN);

    printf("[Setup] Interruptions\n");
    gdtSetup();
    idtSetup();
    irqSetup();
    pitSetup(HZ);

    // https://www.gnu.org/software/grub/manual/multiboot/multiboot.html#Boot-information-format
    if (magic == MULTIBOOT_BOOTLOADER_MAGIC) { // Get loaded by Grub with mutliboot version 1
        multiboot_info_t *mbi = (multiboot_info_t *)addr;
        /* Are mem_* valid? */
        if (CHECK_FLAG(mbi->flags, 0)) {
            printf("mem_lower = %dKiB, mem_upper %dKiB\n", mbi->mem_lower, mbi->mem_upper);
            upperMemKB = mbi->mem_upper;
        }

        /* Is boot_device valid? */
        if (CHECK_FLAG(mbi->flags, 1)) {
            int disk  = mbi->boot_device >> 24 & 0xff;
            int part1 = mbi->boot_device >> 16 & 0xff;
            int part2 = mbi->boot_device >> 8 & 0xff;
            int part3 = mbi->boot_device & 0xff;
            printf("boot_device = 0x%x (0x0 for floppy 0x80 for disk) part %d %d %d\n", disk,
                   part1, part2, part3);
        }

        if (CHECK_FLAG(mbi->flags, 3)) {
            if (mbi->mods_count > 0) {
                multiboot_module_t *mod;
                uint32_t i;

                printf("mods_count = %d, mods_addr = 0x%x\n", (int)mbi->mods_count,
                       (int)mbi->mods_addr);
                for (i = 0, mod = (multiboot_module_t *)mbi->mods_addr; i < mbi->mods_count;
                     i++, mod++)
                    printf(" mod_start = 0x%x, mod_end = 0x%x, cmdline = %s\n",
                           (unsigned)mod->mod_start, (unsigned)mod->mod_end,
                           (char *)mod->cmdline);
            }
        }

        if (CHECK_FLAG(mbi->flags, 6)) {
            memMapAvailable = 1;
        }

        if (CHECK_FLAG(mbi->flags, 9)) {
            printf("Loaded by %s. ", mbi->boot_loader_name);
        }

        /* Is the command line passed? */
        if (CHECK_FLAG(mbi->flags, 2)) {
            printf("cmdline = %s\n", (char *)mbi->cmdline);
        }

        if (CHECK_FLAG(mbi->flags, 12)) {
            printf("Re configure Framebuffer from 0x%llx size (%dx%d) pitch %d bpp %d\n",
                   mbi->framebuffer_addr, mbi->framebuffer_width, mbi->framebuffer_height,
                   mbi->framebuffer_pitch, mbi->framebuffer_bpp);
            VGAConfigure(mbi->framebuffer_addr, mbi->framebuffer_width,
                         mbi->framebuffer_height);
        }
    }

    if (upperMemKB == 0) {
        printf("Cannot get upper phy mem bound. Using default value 32MB\n");
        upperMemKB = 32 * 1024;
    }

    printf("[Setup] Mem\n");

    memSetup(upperMemKB, &firstUsedByMem, &lastUsedByMem);

    if (memMapAvailable) {
        multiboot_info_t *mbi             = (multiboot_info_t *)addr;
        struct multiboot_mmap_entry *mmap = (struct multiboot_mmap_entry *)mbi->mmap_addr;
        uint size = mbi->mmap_length / sizeof(struct multiboot_mmap_entry);

        pr_devel("mmap buffer at 0x%x with %d entries\n", mbi->mmap_addr, size);

        for (uint i = 0; i < size; i++) {
            printf("   base_addr 0x%llx, length = 0x%llx, type = 0x%x\n", mmap[i].addr,
                   mmap[i].len, (uint32_t)mmap[i].type);
            // Consider low memory taken (https://wiki.osdev.org/Detecting_Memory_(x86). For
            // example by VGA
            // Turns out linux and windows do the same !
            // https://lore.kernel.org/lkml/MWHPR21MB159330952629D36EEDE706B3D7379@MWHPR21MB1593.namprd21.prod.outlook.com/
            if (mmap[i].addr < 0x100000) {
                printf("    -> skipping\n");
                continue;
            }
            memAddBank(max(mmap[i].addr, (multiboot_uint64_t)lastUsedByMem),
                       mmap[i].addr + mmap[i].len, mmap[i].type == MULTIBOOT_MEMORY_AVAILABLE);
        }
    } else {
        printf("Cannot get memory Mapping information, using default value\n");
        memAddBank(lastUsedByMem, upperMemKB * 1024, 1);
    }
    printf("%d pages used by kernel(0x%x->0x%x))",
           (lastUsedByMem - firstUsedByMem) / PAGE_SIZE, firstUsedByMem, lastUsedByMem);
    printf(" (%d pages for MM)\n", (lastUsedByMem - (paddr_t)&__ld_kernel_end) / PAGE_SIZE);

#ifdef RUN_TEST
    testPhymem();
#endif
    printf("[Setup] Pagination\n");
    pagingSetup(firstUsedByMem, lastUsedByMem);
    VGAMap();

    printf("[Setup] IRQ handlers\n");
    irqSetRoutineWrapped(IRQ_KEYBOARD, keyboard_do_irq);

    printf("[Setup] HW interrupts\n");
    // Enabling the HW interrupts
    exceptionSetup();
    asm volatile("sti\n");

    printf("[Setup] Serial link (115200)\n");
    serialSetup(115200);

    printf("[Setup] allocation system\n");
    areaInit(firstUsedByMem, lastUsedByMem, _stack_bottom, _stack_top);

    mmuContextSetup();
    cpu_context_subsystem_setup();

    printf("[Setup] thread system\n");
    threadSetup(_stack_bottom, (_stack_top - _stack_bottom + 1));
    threadCreate("idle ", idleThread, NULL);
    processSetup();
    syscallSetup();

    irqSetRoutine(IRQ_TIMER, pit_handler);

    ATAInit();
#ifdef RUN_TEST
    run_test();
#endif
    printf("\nSystem init done: ");

    {
        uint free, used;
        memGetStat(&free, &used);
        printf("%dKB free %dKB Used\n", free * (PAGE_SIZE / 1024), used * (PAGE_SIZE / 1024));
    }

    loadUserSpace();
    // There is no real caller behind this point
    // So finish this by ourself
    threadExit();
}