#include <unistd.h>
#include <libreborn/libreborn.h>
#include <string>
#include <sys/mman.h>

#include "guest.h"

// Syscall Method
static uint32_t trampoline_syscall(const uint32_t id, const uint32_t length, const unsigned char *args) {
    // Make Syscall
    const long ret = syscall(TRAMPOLINE_SYSCALL, id, length, args);
    if (ret == -1) {
        // Error
        ERR("Trampoline Error: %s", strerror(errno));
    }
    // Return
    return *(uint32_t *) args;
}

// Pipe Method (Native Trampoline Only)
static int get_pipe(const char *env) {
    const char *value = getenv(env);
    if (value == nullptr) {
        IMPOSSIBLE();
    }
    const std::string str = value;
    return std::stoi(str);
}
static uint32_t trampoline_pipe(const uint32_t id, const bool allow_early_return, const uint32_t length, const unsigned char *args) {
    // Get Pipes
    static int arguments_pipe = -1;
    static int return_value_pipe = -1;
    if (arguments_pipe == -1) {
        arguments_pipe = get_pipe(TRAMPOLINE_ARGUMENTS_PIPE_ENV);
        return_value_pipe = get_pipe(TRAMPOLINE_RETURN_VALUE_PIPE_ENV);
    }
    // Write Command
    const trampoline_pipe_arguments cmd = {
        .id = id,
        .allow_early_return = allow_early_return,
        .length = length
    };
    if (write(arguments_pipe, &cmd, sizeof(trampoline_pipe_arguments)) != sizeof(trampoline_pipe_arguments)) {
        ERR("Unable To Write Trampoline Command");
    }
    // Write Arguments
    size_t position = 0;
    while (position < length) {
        const ssize_t ret = write(arguments_pipe, args + position, length - position);
        if (ret == -1) {
            ERR("Unable To Write Trampoline Arguments");
        } else {
            position += ret;
        }
    }
    if (allow_early_return) {
        return 0;
    }
    // Return
    uint32_t ret;
    if (read(return_value_pipe, &ret, sizeof(uint32_t)) != sizeof(uint32_t)) {
        ERR("Unable To Read Trampoline Return Value");
    }
    return ret;
}

// Main Function
uint32_t _raw_trampoline(const uint32_t id, const bool allow_early_return, const uint32_t length, const unsigned char *args) {
    // Configure Method
    static bool use_syscall = getenv(TRAMPOLINE_ARGUMENTS_PIPE_ENV) == nullptr;
    // Use Correct Method
    if (use_syscall) {
        return trampoline_syscall(id, length, args);
    } else {
        return trampoline_pipe(id, allow_early_return, length, args);
    }
}