module main

import x.encoding.asn1

// This example takes more complex scenario, in the sense of nested wrapping, the use of
// other class Element supported in this module.
//
// This examples is taken from ITU-T X.690 Information technology – ASN.1 encoding rules:
// Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and
// Distinguished Encoding Rules (DER) document.
//
// Especially from Annex A. Example of encodings of the document.

// from A.1 ASN.1 description of the record structure.
// The structure of the hypothetical personnel record is formally described below using ASN.1 specified in
// ITU-T Rec. X.680 | ISO/IEC 8824-1 for defining types.
//
// PersonnelRecord ::= [APPLICATION 0] IMPLICIT SET {
//      name            Name,
//      title           [0] VisibleString,
//      number          EmployeeNumber,
//      dateOfHire      [1] Date,
//      nameOfSpouse    [2] Name,
//      children        [3] IMPLICIT SEQUENCE OF ChildInformation DEFAULT {}
// }
//
struct PersonnelRecord {
    name           Name
    title          asn1.VisibleString
    number         EmployeeNumber
    date_of_hire   Date
    name_of_spouse Name
    children       asn1.SequenceOf[ChildInformation]
}

fn (pr PersonnelRecord) tag() asn1.Tag {
    return asn1.default_set_tag
}

fn (pr PersonnelRecord) payload() ![]u8 {
    mut out := []u8{}
    out << asn1.encode(pr.name)!
    out << asn1.encode_with_options(pr.title, 'context_specific:0;explicit;inner:26')!
    out << asn1.encode(pr.number)!
    out << asn1.encode_with_options(pr.date_of_hire,
        'context_specific: 1; explicit; inner:application,false,3')!
    out << asn1.encode_with_options(pr.name_of_spouse,
        'context_specific: 2; explicit; inner:application,true,1')!
    out << asn1.encode_with_options(pr.children, 'context_specific: 3; implicit; inner:16')!

    return out
}

// deserializer of PersonellRecord bytes
fn PersonnelRecord.decode(bytes []u8) !PersonnelRecord {
    // we perfrom decoding as a reverse of the serialization with the same options.
    // after that, we get an Element (with the Set type of PersonellRecord)
    el := asn1.decode_with_options(bytes, 'application:0;implicit;inner:17')!
    assert el.tag() == asn1.default_set_tag
    set := el.into_object[asn1.Set]()!

    // fields is series of element ([]Element), PersonellRecord fields
    fields := set.fields()

    // we turn series of element into underlying desired type.
    // its rather clumsy to transforms it, because Sequenve (and Set) fields is an []Element, so you should care
    // to turn this into desired object
    name_app := fields[0].into_object[asn1.ApplicationElement]()!
    name := Name(name_app)

    // Title
    title_elem := fields[1].unwrap_with_options('context_specific:0;explicit;inner:26')!
    title := title_elem.into_object[asn1.VisibleString]()!

    // EmployeNumber
    emp_num := fields[2].into_object[asn1.ApplicationElement]()!
    employe_number := EmployeeNumber(emp_num)

    // dateOfHire
    doh :=
        fields[3].unwrap_with_options('context_specific: 1; explicit; inner:application,false,3')!
    doh_app := doh.into_object[asn1.ApplicationElement]()!
    date_of_hire := Date(doh_app)

    // nameOfSpouse
    nosp :=
        fields[4].unwrap_with_options('context_specific: 2; explicit; inner:application,true,1')!
    nosp_app := nosp.into_object[asn1.ApplicationElement]()!
    name_of_spouse := Name(nosp_app)

    // The children is Sequence of Set, first we unwrap it then turn into sequence.
    children := fields[5].unwrap_with_options('context_specific: 3; implicit; inner:16')!
    children_seq := children.into_object[asn1.Sequence]()!
    childset_fields := children_seq.fields() // []Element

    mut childset := []ChildInformation{}
    for item in childset_fields {
        // item is an Element
        obj := item.into_object[asn1.Set]()!
        i := ChildInformation.from_set(obj)!
        childset << i
    }

    pr := PersonnelRecord{
        name:           name
        title:          title
        number:         employe_number
        date_of_hire:   date_of_hire
        name_of_spouse: name_of_spouse
        children:       asn1.SequenceOf.from_list[ChildInformation](childset)!
    }
    return pr
}

// ChildInformation ::= SET {
//      name            Name,
//      dateOfBirth     [0] Date
// }
//
// Name ::= [APPLICATION 1] IMPLICIT SEQUENCE {
//      givenName       VisibleString,
//      initial         VisibleString,
//      familyName      VisibleString
// }
//
// EmployeeNumber ::= [APPLICATION 2] IMPLICIT INTEGER
// Date ::= [APPLICATION 3] IMPLICIT VisibleString -- YYYYMMDD

// ChildInformation ::= SET {
//      name            Name,
//      dateOfBirth     [0] Date
// }
struct ChildInformation {
    name          Name
    date_of_birth Date
}

// s should Set with series of Element with []ChildInformation within underlying fields.
fn ChildInformation.from_set(s asn1.Set) !ChildInformation {
    if s.fields().len != 2 {
        return error('Bad ChildInformation set')
    }
    fields := s.fields() // serialized name and dateOfBirth of ChildInformation
    name := fields[0].into_object[asn1.ApplicationElement]()!
    doh :=
        fields[1].unwrap_with_options('context_specific: 0; explicit; inner:application,false,3')!
    date := doh.into_object[asn1.ApplicationElement]()!
    ch := ChildInformation{
        name:          Name(name)
        date_of_birth: Date(date)
    }
    return ch
}

fn (ci ChildInformation) tag() asn1.Tag {
    return asn1.default_set_tag
}

fn (ci ChildInformation) payload() ![]u8 {
    mut out := []u8{}
    out << asn1.encode(ci.name)!
    out << asn1.encode_with_options(ci.date_of_birth,
        'context_specific: 0; explicit; inner:application,false,3')!

    return out
}

// EmployeeNumber ::= [APPLICATION 2] IMPLICIT INTEGER
type EmployeeNumber = asn1.ApplicationElement

fn EmployeeNumber.new(val asn1.Integer) !asn1.ApplicationElement {
    return asn1.ApplicationElement.from_element(val, 2, .implicit)!
}

// Date ::= [APPLICATION 3] IMPLICIT VisibleString -- YYYYMMDD
type Date = asn1.ApplicationElement

fn Date.new(val asn1.VisibleString) !asn1.ApplicationElement {
    return asn1.ApplicationElement.from_element(val, 3, .implicit)!
}

// Name ::= [APPLICATION 1] IMPLICIT SEQUENCE {
//      givenName       VisibleString,
//      initial         VisibleString,
//      familyName      VisibleString
// }
type Name = asn1.ApplicationElement

fn Name.new(el NameEntry) !asn1.ApplicationElement {
    return asn1.ApplicationElement.from_element(el, 1, .implicit)!
}

struct NameEntry {
    given_name  asn1.VisibleString
    initial     asn1.VisibleString
    family_name asn1.VisibleString
}

fn (n NameEntry) tag() asn1.Tag {
    return asn1.default_sequence_tag
}

fn (n NameEntry) payload() ![]u8 {
    mut out := []u8{}
    out << asn1.encode(n.given_name)!
    out << asn1.encode(n.initial)!
    out << asn1.encode(n.family_name)!

    return out
}

// The value of John Smith's personnel record is formally described below using ASN.1.
// { name {givenName "John",initial "P",familyName "Smith"},
//        title     "Director",
//        number     51,
//        dateOfHire "19710917",
//        nameOfSpouse {givenName "Mary",initial "T",familyName "Smith"},
//        children {
//            { name {givenName "Ralph",initial "T",familyName "Smith"},
//              dateOfBirth "19571111"
//            },
//            { name {givenName "Susan",initial "B",familyName "Jones"},
//              dateOfBirth "19590717"
//            }
//        }
//    }

// Representation of this record value
//
// 60 8185
//        61 10     1A 04 'John'            // name
//                1A 01 'P'
//                1A 05 'Smith'
//        A0 0A    1A 08 'Director'         // title
//        42 01    33                        // number
//        A1 0A    43 08 '19710917'        // dateOfHire
//        A2 12    61 10     1A     04 'Mary'     // nameOfSpouse
//                        1A    01    'T'
//                        1A    05    'Smith'
//        A3 42    31 1F    61    11    1A 05 'Ralph'    => 52 61 6c 70 68 // children
//                                1A 01 'T'          => 54
//                                1A 05 'Smith'    => 53 6d 69 74 68
//                        A0    0A    43 08 '19571111' => 31 39 35 37 31 31 31 31
//                31 1F    61    11    1A 05 'Susan'    => 53 75 73 61 6e
//                                1A 01 'B'        => 42
//                                1A 05 'Jones'    => 4a 6f 6e 65 73
//                        A0    0A    43 08 '19590717' => 31 39 35 39 30 37 31 37

fn main() {
    // We detailed every pieces of element

    // PersonnelRecord.name
    pr_name := Name.new(NameEntry{
        given_name:  asn1.VisibleString.new('John')!
        initial:     asn1.VisibleString.new('P')!
        family_name: asn1.VisibleString.new('Smith')!
    })!
    //        61 10     1A 04 'John'    => 4a 6f 68 6e            // name
    //                1A 01 'P'         => 50    
    //                1A 05 'Smith'    => 53 6d 69 74 68
    pr_name_bytes := [u8(0x61), 0x10, 0x1A, 0x04, 0x4a, 0x6f, 0x68, 0x6e, 0x1A, 0x01, 0x50, 0x1A,
        0x05, 0x53, 0x6d, 0x69, 0x74, 0x68]

    assert asn1.encode(pr_name)! == pr_name_bytes

    // PersonnelRecord.title
    //        A0 0A    1A 08 'Director' => 44 69 72 65 63 74 6f 72    // title
    title := asn1.VisibleString.new('Director')!
    title_bytes := [u8(0xA0), 0x0A, 0x1A, 0x08, u8(0x44), 0x69, 0x72, 0x65, 0x63, 0x74, 0x6f, 0x72]
    assert asn1.encode_with_options(title, 'context_specific:0;explicit;inner:26')! == title_bytes

    // PersonnelRecord.EmployeeNumber
    //        42 01    33                        // number
    emp_num := EmployeeNumber.new(asn1.Integer.from_int(51))!
    emp_bytes := [u8(0x42), 0x01, 0x33]
    assert asn1.encode(emp_num)! == emp_bytes

    // PersonnelRecord.dateOfHire
    //        A1 0A    43 08 '19710917'    => 31 39 37 31 30 39 31 37    // dateOfHire
    // dateOfHire      [1] Date,
    doh := Date.new(asn1.VisibleString.new('19710917')!)!
    doh_bytes := [u8(0xA1), 0x0A, 0x43, 0x08, 0x31, 0x39, 0x37, 0x31, 0x30, 0x39, 0x31, 0x37]
    assert asn1.encode_with_options(doh, 'context_specific: 1; explicit; inner:application,false,3')! == doh_bytes

    // PersonnelRecord.nameOfSpouse
    //        A2 12    61 10     1A     04 'Mary'    => 4d 61 72 79     // nameOfSpouse
    //                        1A    01    'T'        => 54
    //                        1A    05    'Smith'    => 53 6d 69 74 68
    nosp := Name.new(NameEntry{
        given_name:  asn1.VisibleString.new('Mary')!
        initial:     asn1.VisibleString.new('T')!
        family_name: asn1.VisibleString.new('Smith')!
    })!
    nosp_bytes := [u8(0xA2), 0x12, 0x61, 0x10, 0x1A, 0x04, 0x4d, 0x61, 0x72, 0x79, 0x1A, 0x01,
        0x54, 0x1A, 0x05, 0x53, 0x6d, 0x69, 0x74, 0x68]
    //      nameOfSpouse    [2] Name,
    assert asn1.encode_with_options(nosp, 'context_specific: 2; explicit; inner:application,true,1')! == nosp_bytes

    // { name {givenName "Ralph",initial "T",familyName "Smith"},
    //              dateOfBirth "19571111"
    //            },
    childinfo0 := ChildInformation{
        name:          Name.new(NameEntry{
            given_name:  asn1.VisibleString.new('Ralph')!
            initial:     asn1.VisibleString.new('T')!
            family_name: asn1.VisibleString.new('Smith')!
        })!
        date_of_birth: Date.new(asn1.VisibleString.new('19571111')!)!
    }
    // 31 1F    61    11    1A 05 'Ralph'    => 52 61 6c 70 68
    //                    1A 01 'T'          => 54
    //                    1A 05 'Smith'    => 53 6d 69 74 68
    //            A0    0A    43 08 '19571111' => 31 39 35 37 31 31 31 31
    ch0_bytes := [u8(0x31), 0x1F, 0x61, 0x11, 0x1A, 0x05, 0x52, 0x61, 0x6c, 0x70, 0x68, 0x1A, 0x01,
        0x54, 0x1A, 0x05, 0x53, 0x6d, 0x69, 0x74, 0x68, 0xA0, 0x0A, 0x43, 0x08, 0x31, 0x39, 0x35,
        0x37, 0x31, 0x31, 0x31, 0x31]
    assert asn1.encode(childinfo0)! == ch0_bytes

    childinfo1 := ChildInformation{
        name:          Name.new(NameEntry{
            given_name:  asn1.VisibleString.new('Susan')!
            initial:     asn1.VisibleString.new('B')!
            family_name: asn1.VisibleString.new('Jones')!
        })!
        date_of_birth: Date.new(asn1.VisibleString.new('19590717')!)!
    }
    //                31 1F    61    11    1A 05 'Susan'    => 53 75 73 61 6e
    //                                1A 01 'B'        => 42
    //                                1A 05 'Jones'    => 4a 6f 6e 65 73
    //                        A0    0A    43 08 '19590717' => 31 39 35 39 30 37 31 37
    ch1_bytes := [u8(0x31), 0x1F, 0x61, 0x11, 0x1A, 0x05, 0x53, 0x75, 0x73, 0x61, 0x6e, 0x1A, 0x01,
        0x42, 0x1A, 0x05, 0x4a, 0x6f, 0x6e, 0x65, 0x73, 0xA0, 0x0A, 0x43, 0x08, 0x31, 0x39, 0x35,
        0x39, 0x30, 0x37, 0x31, 0x37]
    assert asn1.encode(childinfo1)! == ch1_bytes

    // PersonnelRecord.children
    children := asn1.SequenceOf.from_list[ChildInformation]([childinfo0, childinfo1])!
    //        A3 42    31 1F    61    11    1A 05 'Ralph'    => 52 61 6c 70 68 // children
    //                                1A 01 'T'          => 54
    //                                1A 05 'Smith'    => 53 6d 69 74 68
    //                        A0    0A    43 08 '19571111' => 31 39 35 37 31 31 31 31
    //                31 1F    61    11    1A 05 'Susan'    => 53 75 73 61 6e
    //                                1A 01 'B'        => 42
    //                                1A 05 'Jones'    => 4a 6f 6e 65 73
    //                        A0    0A    43 08 '19590717' => 31 39 35 39 30 37 31 37
    children_bytes := [u8(0xA3), 0x42, u8(0x31), 0x1F, 0x61, 0x11, 0x1A, 0x05, 0x52, 0x61, 0x6c,
        0x70, 0x68, 0x1A, 0x01, 0x54, 0x1A, 0x05, 0x53, 0x6d, 0x69, 0x74, 0x68, 0xA0, 0x0A, 0x43,
        0x08, 0x31, 0x39, 0x35, 0x37, 0x31, 0x31, 0x31, 0x31, u8(0x31), 0x1F, 0x61, 0x11, 0x1A,
        0x05, 0x53, 0x75, 0x73, 0x61, 0x6e, 0x1A, 0x01, 0x42, 0x1A, 0x05, 0x4a, 0x6f, 0x6e, 0x65,
        0x73, 0xA0, 0x0A, 0x43, 0x08, 0x31, 0x39, 0x35, 0x39, 0x30, 0x37, 0x31, 0x37]
    assert asn1.encode_with_options(children, 'context_specific: 3; implicit; inner:16')! == children_bytes

    // PersonnelRecord entries
    pr := PersonnelRecord{
        name:           pr_name
        title:          title
        number:         emp_num
        date_of_hire:   doh
        name_of_spouse: nosp
        children:       children
    }

    mut expected_record_bytes := [u8(0x60), 0x81, 0x85]
    expected_record_bytes << pr_name_bytes
    expected_record_bytes << title_bytes
    expected_record_bytes << emp_bytes
    expected_record_bytes << doh_bytes
    expected_record_bytes << nosp_bytes
    expected_record_bytes << children_bytes

    // PersonnelRecord ::= [APPLICATION 0] IMPLICIT SET {
    pr_record_output := asn1.encode_with_options(pr, 'application:0;implicit;inner:17')!
    assert pr_record_output == expected_record_bytes

    pr_record := PersonnelRecord.decode(pr_record_output)!
    pr_record_encoded_back :=
        asn1.encode_with_options(pr_record, 'application:0;implicit;inner:17')!

    dump(pr_record_encoded_back == expected_record_bytes) // true
}