/*
 * Gift Card Application
 * Original Author: Shoddycorp's Cut-Rate Contracting
 * Maintainer:
 * Comments added by: Justin Cappos (JAC)
 * Modification Date: 8 July 2020
 */

// The purpose of this app is to read in gift card data.  The format of a gift 
// card looks like this:
//
// thisgiftcard:
//   num_bytes[32 bits]:giftcard_data (see below)
//
// giftcarddata:
//   merchant_id [32 bytes]:customer_id [32 bytes]:num_gift_card_records[32 bits]:gift_card_record_data[variable length]
//
// giftcardrecorddata:
//   num_bytes[32 bits]
//   type_of_record 
//   gift_card_amount_change OR gift_card_message
//
// giftcardamountchange:  Adds or removes money from the card
//   amount_added[32 bits]    Note, amounts are in 1 yen
//   merchant_signature[32 bytes]  USED IFF amount_added is POSITIVE
//
// giftcardmessage:
//   just a null terminated C string.
// 
// giftcardprogram: (BETA)
//   message[32 bytes]
//   program[256 bytes]
//
// So some actual example files might look like this:
//  [bytes][merchant_id][customer_id][num_records][bytes][type][AMOUNT][sig]
//    116     456...       524...         1          44      1   2000   fed...
//  [bytes][merchant_id][customer_id][num_records][bytes][type][AMOUNT][sig][bytes][type][message]
//    124    abc...        123...         2          44      1   1500   fed... 24    2   "Happy Birthday!\0"
//
// [BETA] program spec for animated text feature
// customer requested. Electronic greeting cards use THX-1138 miroprocessor and
// can support small programs to animate the text being displayed. Real processor
// has more opcodes than this but for beta demo just implement these
// programs operate on the message buffer
// note!! it is the gift card producers job to make sure that
// programs in the gift card are VALID
// each "instruction" is 3 bytes
// arithmetic instructions set the zero flag if the result is 0
// opcode (1 byte) arg1 (1 byte) arg2 (1 byte)
// 0x00  no-op (if there is extra space at end of program this should be used)
// 0x01  get current char into register "arg1" (16 registers)
// 0x02  put registar "arg1" into current char
// 0x03  move cursor by "arg1" bytes (can be negative)
// 0x04  put constant "arg1" into register "arg2"
// 0x05  xor register "arg1" with register "arg2" and store result in register "arg1"
// 0x06  add register "arg1" to register "arg2" and store result in register "arg1"
// 0x07  display the current message
// 0x08  end program
// 0x09  jump "arg1" bytes relative to the end of this instruction
// 0x10  if the zero flag is set, jump "arg1" bytes relative to the end of this instruction
// 0x11-0xff not used for now

#ifndef GIFTCARD_H
#define GIFTCARD_H

#include <stdint.h>

#define GC_MERCHANT_SIZE 32
#define GC_CUSTOMER_SIZE 32
#define GC_SIGNATURE_SIZE 32
#define GC_PROGRAM_SIZE 256
#define GC_PROGMSG_SIZE 32

enum gift_card_program_op {
    GC_OP_NOP = 0x00,
    GC_OP_GET = 0x01,
    GC_OP_PUT = 0x02,
    GC_OP_MOV = 0x03,
    GC_OP_CON = 0x04,
    GC_OP_XOR = 0x05,
    GC_OP_ADD = 0x06,
    GC_OP_PRN = 0x07,
    GC_OP_END = 0x08,
    GC_OP_JMP = 0x09,
    GC_OP_JCC = 0x10
};

enum gift_card_type {
    GC_AMOUNT = 1,
    GC_MESSAGE = 2,
    GC_PROGRAM = 3,
    GC_LAST
};

char *gift_card_type_str[GC_LAST] = {
    [GC_AMOUNT] = "amount_change",
    [GC_MESSAGE] = "message",
    [GC_PROGRAM] = "animated message",
};

struct gift_card_amount {
    int32_t amount;
    char signature[GC_SIGNATURE_SIZE]; // unused if amount < 0
};

struct gift_card_message {
    char *message_str;
};

struct gift_card_program {
    char message[GC_PROGMSG_SIZE];
    unsigned char program[GC_PROGRAM_SIZE];
};

struct gift_card {
	char merchant_id[GC_MERCHANT_SIZE];
	char customer_id[GC_CUSTOMER_SIZE];
	int number_of_gift_card_records;
	struct gift_card_record **records; // many can exist here.
};

struct gift_card_record {
	enum gift_card_type rec_type;
    union {
        struct gift_card_amount amount;
        struct gift_card_message message;
        struct gift_card_program program;
    };
};

#endif