.include "instr.inc"
.text

.global _start
_start:
    # Get the address of the start of the program
    push_pc
    pop_r3

    # Display the introduction
    ld_r2_r3
    add_r2 (str_intro - _start)
    push_r3
    call PrintStr
    pop_r3

    # Bail if we're not running from the correct address
    cp_r3 _start
    jp_eq main
    ld_r2_r3
    add_r2 (str_wrong_address - _start)
    jp PrintStr

main:
    # Gather the password string
    ld_r2 mem_input
    ld_r1 18
    ld_r0 0
    call MemSet
    ld_r2 str_password_prompt
    call PrintStr
    ld_r2 mem_input
    ld_r3 15
    call ReadStr
    ld_r2 mem_input
    call StrTrim

    # Hash the string
    ld_r2 mem_input
    ld_r0 0x9fc0

hash_loop:
    ldr_r1_r2
    inc_r2
    cp_r1 0

    # r0 = (((r0 * 2) ^ r1) * 2) + r1
    shl_r0
    xor_r0_r1
    shl_r0
    add_r0_r1

    jp_eq decrypt
    jp hash_loop

decrypt:
    # Initialize memory
    str_r0 mem_hash
    ld_r3 mem_encrypted
    ld_r2 mem_decrypted
    ld_r1 0x200
    call MemCpy

    # Decrypt the entire buffer
    ld_r2 mem_decrypted
    ld_r3 0x200 / 2

decrypt_loop:
    call update_hash

    # *r2 -= mem_hash
    ld_r1_r0
    ldr_r0_r2
    xor_r0_r1
    str_r0_r2

    inc_r2
    inc_r2
    dec_r3
    cp_r3 0
    jp_ne decrypt_loop

    # Print out the results
    ld_r2 str_result_start
    call PrintStr
    ld_r2 mem_decrypted
    call PrintStr
    ld_r2 str_result_end
    call PrintStr
    ret

update_hash:
    # mem_hash = (mem_hash * 0x41a7) ^ 0x5555
    ldr_r0 mem_hash
    mul_r0 0x41a7
    xor_r0 0x5555
    str_r0 mem_hash
    ret

str_intro:
    .ascii "GLITCH RESEARCH LABORATORY SELF-CONTAINED ENCRYPTION TOOL\n\0"

str_wrong_address:
    .ascii "PLEASE LOAD ME AT ADDRESS $2000... (EXITING)\n\0"

str_password_prompt:
    .ascii "PLEASE ENTER ENCRYPTION PASSWORD: \0"

str_result_start:
    .ascii "HERE IS THE ENCRYPTED DOCUMENT: "
str_result_end:
    .ascii "\n--\n\0"

mem_input:
    .ascii "________________\0\0"

mem_hash:
    .ascii "__"

    # Padding
    .ascii "33333333"

mem_encrypted:
    .byte 0xfb, 0x72, 0x3a, 0x22, 0x21, 0x4b, 0x6a, 0xc2
    .byte 0x28, 0xe6, 0xe4, 0xc1, 0xa7, 0x25, 0xb6, 0xe0
    .byte 0x98, 0xb2, 0x0a, 0xe0, 0x9b, 0xab, 0xc1, 0x84
    .byte 0xb8, 0x2d, 0x8f, 0xd8, 0x7e, 0x07, 0x3a, 0xcb
    .byte 0xc9, 0xf0, 0xf5, 0x38, 0x51, 0x43, 0xed, 0x52
    .byte 0xf8, 0x44, 0xe4, 0xc2, 0x50, 0x22, 0x27, 0x2a
    .byte 0x65, 0x44, 0x81, 0x79, 0xc2, 0x6c, 0xb4, 0xaf
    .byte 0xd9, 0x9d, 0x7c, 0x74, 0xb3, 0x58, 0xea, 0xcd
    .byte 0x69, 0xe2, 0xa2, 0xdf, 0xe7, 0xca, 0xc4, 0x65
    .byte 0xe0, 0xe8, 0xf3, 0xbe, 0xee, 0x97, 0x68, 0xad
    .byte 0x61, 0x0e, 0x27, 0x78, 0x32, 0x86, 0x6d, 0x5c
    .byte 0x02, 0xc2, 0x6e, 0xd1, 0xdf, 0x93, 0x14, 0x4d
    .byte 0xcb, 0x1a, 0x90, 0xf4, 0x20, 0x95, 0xc0, 0xd3
    .byte 0x1d, 0xe8, 0x73, 0x2b, 0xdb, 0xaf, 0xae, 0x74
    .byte 0x7a, 0x1d, 0x50, 0x4a, 0xa6, 0x9d, 0x56, 0xcc
    .byte 0xb5, 0x5d, 0x07, 0xd1, 0x04, 0xa7, 0x16, 0x5c
    .byte 0x1d, 0x40, 0x4e, 0x65, 0x51, 0xf2, 0x68, 0x0a
    .byte 0x4a, 0xb3, 0x56, 0x56, 0xc1, 0x51, 0x1f, 0x0f
    .byte 0xc2, 0x7d, 0x4b, 0x29, 0x5b, 0x58, 0x1d, 0x2f
    .byte 0xff, 0x66, 0xc0, 0x3c, 0xbb, 0xbb, 0x34, 0x93
    .byte 0x30, 0xe6, 0x34, 0xb7, 0x8d, 0xd4, 0x4a, 0xa3
    .byte 0xd7, 0x88, 0x00, 0x72, 0xba, 0x13, 0x0c, 0x4d
    .byte 0x97, 0x46, 0xe0, 0xbb, 0x07, 0xa6, 0xef, 0xfa
    .byte 0x12, 0x0a, 0xfe, 0x56, 0xe9, 0x14, 0x2b, 0xda
    .byte 0x64, 0x3c, 0xfe, 0xc5, 0x3c, 0xa3, 0x50, 0x02
    .byte 0x20, 0xb7, 0x20, 0x05, 0x3d, 0xdb, 0xf1, 0x8a
    .byte 0x81, 0x41, 0x4c, 0x24, 0x52, 0x38, 0x8f, 0xb9
    .byte 0x7e, 0x2e, 0x6f, 0x76, 0x1c, 0x3f, 0x97, 0x87
    .byte 0x16, 0xd5, 0xd3, 0xc9, 0x70, 0x92, 0xd7, 0xd2
    .byte 0x47, 0x59, 0xe6, 0x87, 0x12, 0x2c, 0xe0, 0xa5
    .byte 0x6c, 0x17, 0x9c, 0xbe, 0xee, 0xe4, 0xd4, 0x50
    .byte 0xea, 0x94, 0x57, 0x91, 0x4f, 0xb1, 0x57, 0xaa
    .byte 0x46, 0xe9, 0x86, 0x76, 0xd3, 0xf8, 0xb9, 0xa5
    .byte 0x8c, 0x9c, 0x57, 0x56, 0x0a, 0x72, 0x48, 0xc8
    .byte 0x14, 0xb6, 0x8b, 0xf2, 0x48, 0x3c, 0x4d, 0xb5
    .byte 0x3a, 0x48, 0x07, 0xa6, 0xf2, 0x8e, 0xa3, 0x0b
    .byte 0x39, 0x02, 0x75, 0x9b, 0xc8, 0xdc, 0x6f, 0x0a
    .byte 0x75, 0x00, 0x52, 0x6d, 0xbf, 0x77, 0x89, 0x2f
    .byte 0xce, 0xb0, 0x27, 0xef, 0x42, 0x1e, 0x36, 0xe1
    .byte 0x37, 0xc6, 0xf7, 0x77, 0x34, 0x1d, 0x6a, 0xd3
    .byte 0xa7, 0x48, 0x6a, 0xc1, 0x7d, 0xe7, 0x76, 0x8c
    .byte 0x62, 0x8f, 0x62, 0x8c, 0x5c, 0xe4, 0xf1, 0xf3
    .byte 0xfd, 0x5f, 0xb6, 0x9d, 0xb4, 0xd7, 0xa8, 0xa0
    .byte 0xcd, 0xde, 0x8b, 0x72, 0x73, 0xe4, 0xfa, 0xe7
    .byte 0x33, 0x8f, 0x11, 0x1e, 0xaf, 0xd3, 0x40, 0xa7
    .byte 0x86, 0x26, 0xf3, 0x77, 0x4c, 0x6e, 0x2d, 0x2d
    .byte 0xa4, 0x03, 0xc2, 0x74, 0x2e, 0xb3, 0xdd, 0x85
    .byte 0x29, 0x41, 0x90, 0xc3, 0xc7, 0x3a, 0x96, 0xb9
    .byte 0x8e, 0x35, 0xcf, 0x37, 0xc0, 0xc8, 0xff, 0xd5
    .byte 0x8b, 0x9f, 0xa1, 0xd9, 0x0f, 0x8e, 0x8e, 0xc6
    .byte 0x11, 0xc1, 0xc0, 0xc9, 0x9e, 0x5b, 0x9c, 0xa1
    .byte 0x2d, 0xc6, 0x4b, 0xf5, 0x34, 0x65, 0xb4, 0xcc
    .byte 0xac, 0x88, 0xbf, 0x49, 0x43, 0x77, 0xac, 0x8f
    .byte 0x61, 0x71, 0x8e, 0x59, 0x7f, 0x78, 0xd9, 0x73
    .byte 0x41, 0x90, 0x73, 0x8b, 0x8e, 0x93, 0x3f, 0x6e
    .byte 0xdd, 0x2e, 0x37, 0xe8, 0x72, 0x43, 0xa1, 0xf3
    .byte 0xa9, 0xfe, 0x7f, 0x98, 0xf3, 0xa5, 0x98, 0x43
    .byte 0xe5, 0x60, 0xb9, 0x5d, 0xbd, 0xba, 0x3f, 0xae
    .byte 0x71, 0xf6, 0xed, 0xc1, 0xfe, 0x8f, 0x2d, 0x15
    .byte 0xd9, 0xc6, 0xf7, 0x57, 0x83, 0x57, 0x7e, 0x10
    .byte 0xb6, 0xc3, 0x76, 0x29, 0xb1, 0x10, 0x12, 0x1e
    .byte 0xea, 0xa1, 0x15, 0x81, 0x9c, 0x22, 0x5f, 0x8a
    .byte 0xf3, 0xff, 0x1c, 0x37, 0x4e, 0x57, 0x1b, 0x26
    .byte 0x64, 0xb7, 0xca, 0x7c, 0xc8, 0x57, 0xd9, 0x57

mem_decrypted:
    .fill 0x200, 1, 0