// Copyright (c) 2022, 2024 blackshirt. All rights reserved.
// Use of this source code is governed by a MIT License
// that can be found in the LICENSE file.
module asn1

const max_choices_size = 255
const default_choices_size = 64

// ASN.1 CHOICE
//
// Choice is an ASN.1 Element
pub struct Choice {
mut:
    size    int = default_choices_size
    choosen Element
    choices []Element
}

// new creates a new choice element. It accepts el as a choosen element
// and choices as a source of possible choices list.
pub fn Choice.new(el Element, choices []Element) !Choice {
    c := Choice{
        choosen: el
        choices: choices
    }
    c.check()!
    return c
}

// set_size sets the maximal this choices size
pub fn (mut c Choice) set_size(size int) ! {
    if size > max_choices_size {
        return error('Your size exceed max_choices_size')
    }
    c.size = size
    c.check()!
}

// choose chooses some element for as a choosen element for the choice c.
pub fn (mut c Choice) choose(some Element) ! {
    mut within := false
    for el in c.choices {
        if el.equal(some) {
            within = true
        }
    }
    if within {
        c.choosen = some
        return
    }
    return error('element not within choices')
}

fn (c Choice) check() ! {
    if c.choices.len == 0 {
        return error('bad choices list')
    }
    if c.choices.len > c.size {
        return error('Your choices list exceed size')
    }
    // check the choosen element is within choices
    filtered := c.choices.filter(it.equal(c.choosen))
    // nothing found, so..its bad choice
    if filtered.len == 0 {
        return error('choosen element not within choices list')
    }
    if filtered.len > 1 {
        return error('multiples element within choices matching with choosen element')
    }
}

// tag returns the tag of choice element.
pub fn (c Choice) tag() Tag {
    return c.choosen.tag()
}

// payload returns the payload of choice element.
pub fn (c Choice) payload() ![]u8 {
    return c.choosen.payload()!
}