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#import "Basic";
#import "POSIX";

// This prototype is suposed to allow me to use the "open" posix syscall
// that returns a file-descriptor (fd) that can then be used by the mmap
// syscall that allows to map a file to memory.
//
// Syscall info: https://filippo.io/linux-syscall-table/

// TODO
// - On mmap_file and munmap_file use get_error_string as in the windows version. This is defined in ./modules/System.jai.
// - Check if the strings being passed to these syscalls require any processing to be a C_string.
// - Check what's the best return type for syscalls... is it OS dependent?
// - File structure
// modules/POSIX - where a lot of POSIX stuff (constants and structs) is defined, e.g.: `SYS_open :: 5;`
// modules/System - where "Windows" or "POSIX" or "Objective -> macos" modules are imported... I suspect we import "System" if trying to target all OSes.
// modules/Linux - defines some unix stuff (constants and structs) and then imports "POSIX".
// 
// Seems that, each functionality may directly implement for all OSes, instead of using a OS independent layer.

main :: () {
    
    //sys_exit(-1);
    size_stat, error_stat := sys_stat("./dummy");
    print("> dymmy has stat size % widh error %\n", size_stat.st_size, error_stat);
    
    fd, error_open := sys_open("./dummy", O_RDONLY, O_RDONLY);
    print("> opened dummy with fd % and errno %\n", fd, error_open);
    if fd < 0 return;
    
    
    //LOOPER :: "\\|/-";
    //idx := 0;
    //loop: string;
    //loop.count = 1;
    //for 0..3 {
        //sleep_milliseconds(1000);
        //loop.data = *LOOPER.data[idx];
        //idx = (idx + 1) % LOOPER.count;
        //print("\rlooping %", loop);
    //}
    
    
    size_lseek, error_lseek := sys_lseek(fd, 0, SEEK_END);
    print("\r> dummy has lseek size % with error %\n", size_lseek, error_lseek);
    
    size_fstat, error_fstat := sys_fstat(fd);
    print("\r> dummy has fstat size % with error %\n", size_fstat.st_size, error_fstat);
    
    error_close := sys_close(fd);
    print("\r> close(%) with errno %\n", fd, error_close);
    
    print("---\n");
    error :s64;
    fd, error = sys_open("./fail", O_RDONLY, O_RDONLY);
    print("$ open(fail) returned fd % and error %\n", fd, error);
    error = sys_close(456);
    print("$ close(456) returned error %\n", error);
}


sys_stat :: (path: string) -> result: stat_t, error: s64{
    print("\r# sys_stat\n"); // TODO
    #if OS == .LINUX {
        SYS_STAT :: 4;
        stats: stat_t = ---;
        result: s64 = ---;
        #if CPU == .X64 {
            print("\r# LINUX:ASM\n"); // TODO
            path_p:   *s8 = xx path.data;
            stats_p := *stats;
            #asm SYSCALL_SYSRET {
            mov rax:    gpr === a,  SYS_STAT;
            mov rdi:    gpr === di, path_p;
            mov rsi:    gpr === si, stats_p;
            syscall
                rcx: gpr === c,     // Implicitly used by syscall to store RIP
                r11: gpr === 11,    // Implicitly used by syscall to store RFLAGS
                rax, rdi, rsi;
            mov result, rax;
            }
            if result < 0
                return .{}, -result; // Error.
            else
                return stats, 0; // OK.
        } else {
            print("\r# LINUX:LIBC\n"); // TODO
            path_p:   *s8 = xx path.data;
            error := syscall(SYS_STAT, path_p, *stats);
            if error < 0
                return .{}, errno(); // Error.
            else
                return stats, 0; // OK.
        }
    } else {
        print("NOT IMPLEMENTED\n", to_standard_error = true);
        return .{}, -1;
    }
}

sys_fstat :: (file_descriptor: s64) -> result: stat_t, error: s64{
    print("\r# sys_fstat\n"); // TODO
    #if OS == .LINUX {
        SYS_FSTAT :: 5;
        stats: stat_t = ---;
        stats_p := *stats;
        result: s64 = ---;
        #if CPU == .X64 {
            print("\r# LINUX:ASM\n"); // TODO
            #asm SYSCALL_SYSRET {
            mov rax:    gpr === a,  SYS_FSTAT;
            mov rdi:    gpr === di, file_descriptor;
            mov rsi:    gpr === si, stats_p;
            syscall
                rcx: gpr === c,     // Implicitly used by syscall to store RIP
                r11: gpr === 11,    // Implicitly used by syscall to store RFLAGS
                rax, rdi, rsi;
            mov result, rax;
            }
            if result < 0
                return .{}, -result; // Error.
            else
                return stats, 0; // OK.
        } else {
            print("\r# LINUX:LIBC\n"); // TODO
            error := syscall(SYS_FSTAT, file_descriptor, *result);
            if error < 0
                return .{}, errno(); // Error.
            else
                return stats, 0; // OK.
        }
    } else {
        print("NOT IMPLEMENTED\n", to_standard_error = true);
        return .{}, -1;
    }
}

sys_lseek :: (file_descriptor: s64, offset: s64, whence: s64) -> offset_location: s64, error: s64 {
    print("\r# sys_lseek\n"); // TODO
    #if OS == .LINUX {
        SYS_LSEEK :: 8;
        result: s64 = ---;
        #if CPU == .X64 {
            print("\r# LINUX:ASM\n"); // TODO
            #asm SYSCALL_SYSRET {
            mov rax:    gpr === a,  SYS_LSEEK;
            mov rdi:    gpr === di, file_descriptor;
            mov rsi:    gpr === si, offset;
            mov rdx:    gpr === d,  whence;
            //syscall rcx, r11, rax, rdi, rsi, rdx; // TODO Cleanup?
            syscall
                rcx: gpr === c,     // Implicitly used by syscall to store RIP
                r11: gpr === 11,    // Implicitly used by syscall to store RFLAGS
                rax, rdi, rsi, rdx; 
            mov result, rax;
            }
            if result < 0
                return -1, -result; // Error.
            else
                return result, 0; // OK.
        } else {
            print("\r# LINUX:LIBC\n"); // TODO
            result = syscall(SYS_LSEEK, file_descriptor, offset, whence);
            if result < 0
                return -1, errno(); // Error.
            else
                return result, 0; // OK.
        }
    } else {
        print("NOT IMPLEMENTED\n", to_standard_error = true);
        return -1, -1;
    }
}

sys_open :: (path: string, flags: s64, mode: s64) -> file_descriptor: s64, error: s64 {
    print("\r# sys_open\n"); // TODO
    #if OS == .LINUX {
        SYS_OPEN :: 2;
        data:   *s8 = xx path.data;
        result: s64 = ---;
        #if CPU == .X64 {
            print("\r# LINUX:ASM\n"); // TODO
            #asm SYSCALL_SYSRET {
            mov rax:    gpr === a,  SYS_OPEN;
            mov rdi:    gpr === di, data;
            mov rsi:    gpr === si, flags;
            mov rdx:    gpr === d,  mode; // TODO Is this really used?
            //syscall rcx, r11, rax, rdi, rsi, rdx; // TODO Cleanup?
            syscall
                rcx: gpr === c,     // Implicitly used by syscall to store RIP
                r11: gpr === 11,    // Implicitly used by syscall to store RFLAGS
                rax, rdi, rsi, rdx; 
            mov result, rax;
            }
            if result < 0
                return -1, -result; // Error.
            else
                return result, 0; // OK.
        } else {
            print("\r# LINUX:LIBC\n"); // TODO
            result = syscall(SYS_OPEN, data, flags, mode);
            if result < 0
                return -1, errno(); // Error.
            else
                return result, 0; // OK.
        }
    } else {
        print("NOT IMPLEMENTED\n", to_standard_error = true);
        return -1, -1;
    }
}

sys_close :: (file_descriptor: s64) -> error: s64 {
    print("\r# sys_close\n"); // TODO
    #if OS == .LINUX {
        SYS_CLOSE :: 3;
        result: s64 = ---;
        #if CPU == .X64 {
            print("\r# LINUX:ASM\n"); // TODO
            #asm SYSCALL_SYSRET {
                mov rax:    gpr === a,  SYS_CLOSE;
                mov rdi:    gpr === di, file_descriptor;
                syscall
                    rcx: gpr === c,     // Implicitly used by syscall to store RIP
                    r11: gpr === 11,    // Implicitly used by syscall to store RFLAGS
                    rax, rdi;
                mov result, rax;
            }
            return ifx result < 0 then -result else 0;
        } else {
            print("\r# LINUX:LIBC\n"); // TODO
            result = syscall(SYS_CLOSE, file_descriptor);
            return ifx result < 0 then errno() else 0;
        }
    } else {
        print("NOT IMPLEMENTED\n", to_standard_error = true);
        return -1;
    }
}