#define NOB_IMPLEMENTATION
#include "nob.h"
#include <stdbool.h>

#define BUILD_FOLDER "build/"
#define SRC_FOLDER "src/"

bool render_clangd_config(void) {
    Nob_String_Builder tmpl = {0};
    if (!nob_read_entire_file(".clangd.template", &tmpl))
        return false;
    nob_sb_append_null(&tmpl);

    const char *include_path = getenv("I686_ELF_GCC_INCLUDE");
    if (include_path == NULL) {
        nob_log(NOB_ERROR, "I686_ELF_GCC_INCLUDE not set");
        nob_sb_free(tmpl);
        return false;
    }

    const char *needle = "${env:I686_ELF_GCC_INCLUDE}";
    Nob_String_Builder out = {0};

    const char *cursor = tmpl.items;
    const char *found;
    while ((found = strstr(cursor, needle)) != NULL) {
        nob_sb_append_buf(&out, cursor, found - cursor);
        nob_sb_append_cstr(&out, include_path);
        cursor = found + strlen(needle);
    }
    nob_sb_append_cstr(&out, cursor);

    bool ok = nob_write_entire_file(".clangd", out.items, out.count);

    nob_sb_free(tmpl);
    nob_sb_free(out);
    return ok;
}

bool build_assembly(Nob_Cmd *cmd) {
    const char *output = BUILD_FOLDER "boot.o";
    const char *input = SRC_FOLDER "boot.s";
    int rebuild = nob_needs_rebuild1(output, input);

    if (!rebuild)
        return true;

    nob_cmd_append(cmd, "i686-elf-as", "-o", BUILD_FOLDER "boot.o", SRC_FOLDER "boot.s");
    if (!nob_cmd_run(cmd))
        return false;

    return true;
}

bool build_c(Nob_Cmd *cmd) {
    const char *output = BUILD_FOLDER "kernel.o";
    const char *input = SRC_FOLDER "kernel.c";
    int rebuild = nob_needs_rebuild1(output, input);

    if (!rebuild)
        return true;

    nob_cmd_append(cmd,
                   "i686-elf-gcc",
                   "-std=gnu99",
                   "-ffreestanding",
                   "-Wall",
                   "-Wextra",
                   "-O2",
                   "-o", BUILD_FOLDER "kernel.o",
                   "-c", SRC_FOLDER "kernel.c");
    if (!nob_cmd_run(cmd))
        return false;

    return true;
}

bool link_everything(Nob_Cmd *cmd) {
    const char *output = BUILD_FOLDER "kernel";
    const char *input[] = {SRC_FOLDER "linker.ld", BUILD_FOLDER "kernel.o", BUILD_FOLDER "boot.o"};
    int rebuild = nob_needs_rebuild(output, input, NOB_ARRAY_LEN(input));

    if (!rebuild)
        return true;

    Nob_File_Paths objectFiles = {0};
    nob_da_append(&objectFiles, BUILD_FOLDER "kernel.o");
    nob_da_append(&objectFiles, BUILD_FOLDER "boot.o");
    nob_cmd_append(cmd,
                   "i686-elf-gcc",
                   "-T", SRC_FOLDER "linker.ld",
                   "-o", BUILD_FOLDER "kernel",
                   "-ffreestanding",
                   "-O2",
                   "-nostdlib");

    // Add objectFiles as input
    for (size_t i = 0; i < objectFiles.count; ++i) {
        nob_cmd_append(cmd, objectFiles.items[i]);
    }

    nob_cmd_append(cmd, "-lgcc");
    if (!nob_cmd_run(cmd))
        return false;

    return true;
}

bool check_kernel(Nob_Cmd *cmd) {
    nob_cmd_append(cmd, "grub-file", "--is-x86-multiboot", BUILD_FOLDER "kernel");
    if (!nob_cmd_run(cmd))
        return false;

    return true;
}

bool clean_dir(const char *dir_path) {
    Nob_File_Paths children = {0};
    if (!nob_read_entire_dir(dir_path, &children))
        return false;

    bool ok = true;
    for (size_t i = 0; i < children.count; ++i) {
        const char *name = children.items[i];

        if (strcmp(name, ".") == 0 || strcmp(name, "..") == 0)
            continue;

        const char *full_path = nob_temp_sprintf("%s/%s", dir_path, name);
        if (!nob_delete_file(full_path)) {
            clean_dir(full_path);
            nob_delete_file(full_path);
        }
    }

    nob_da_free(children);
    return ok;
}

bool build_bootable_image(Nob_Cmd *cmd) {
    const char *output = BUILD_FOLDER "kernel.iso";
    const char *input[] = {BUILD_FOLDER "kernel", SRC_FOLDER "grub.cfg"};
    int rebuild = nob_needs_rebuild(output, input, NOB_ARRAY_LEN(input));

    if (!rebuild)
        return true;

    if (!nob_mkdir_if_not_exists(BUILD_FOLDER "isodir"))
        return false;
    if (!nob_mkdir_if_not_exists(BUILD_FOLDER "isodir/boot"))
        return false;
    if (!nob_mkdir_if_not_exists(BUILD_FOLDER "isodir/boot/grub"))
        return false;

    nob_cmd_append(cmd, "cp", BUILD_FOLDER "kernel", BUILD_FOLDER "isodir/boot/kernel");
    if (!nob_cmd_run(cmd))
        return false;

    nob_cmd_append(cmd, "cp", SRC_FOLDER "grub.cfg", BUILD_FOLDER "isodir/boot/grub/grub.cfg");
    if (!nob_cmd_run(cmd))
        return false;

    nob_cmd_append(cmd, "grub-mkrescue", "-o", BUILD_FOLDER "kernel.iso", BUILD_FOLDER "isodir");
    if (!nob_cmd_run(cmd))
        return false;

    return true;
}

bool runQemu(Nob_Cmd *cmd) {
    nob_cmd_append(cmd, "qemu-system-i386", "-cdrom", BUILD_FOLDER "kernel.iso");
    if (!nob_cmd_run(cmd))
        return false;
    return true;
}

int main(int argc, char **argv) {
    NOB_GO_REBUILD_URSELF(argc, argv);
    const char *program_name = shift(argv, argc);
    bool clean = false;
    bool run = false; // starts qemu
    bool build = false;
    while (argc > 0) {
        const char *arg = shift(argv, argc);
        if (strcmp(arg, "clean") == 0)
            clean = true;
        if (strcmp(arg, "run") == 0)
            run = true;
        if (strcmp(arg, "build") == 0)
            build = true;
    }

    if (clean) {
        const char *dir_path = BUILD_FOLDER;

        Nob_Dir_Entry dir = {0};
        if (!nob_dir_entry_open(dir_path, &dir)) {
            nob_log(NOB_INFO, "No build directory to clean. Skipping...");
        } else {
            if (!clean_dir(BUILD_FOLDER))
                return 1;
            nob_delete_file(BUILD_FOLDER);
        }
    }

    if (build) {
        if (!nob_mkdir_if_not_exists(BUILD_FOLDER))
            return 1;

        Nob_Cmd cmd = {0};

        if (!render_clangd_config())
            return 1;

        if (!build_assembly(&cmd))
            return 1;
        if (!build_c(&cmd))
            return 1;
        if (!link_everything(&cmd))
            return 1;
        if (!check_kernel(&cmd))
            return 1;
        if (!build_bootable_image(&cmd))
            return 1;
    }

    if (run) {
        Nob_Cmd cmd = {0};
        if (!runQemu(&cmd))
            return 1;
    }

    if (!clean && !build && !run) {
        nob_log(NOB_INFO, "Usage: %s (build || clean || run)", program_name);
        return 1;
    }

    return 0;
}