module main

type SecondTokenizerValue = []rune | Keyword

enum AdvancedTokenType {
    identifier
    keyword
    newline
}

struct SecondTokenizerToken {
    type  AdvancedTokenType
    value ?SecondTokenizerValue
}

enum Keyword {
    module
    import
}

pub struct FileAST {
pub mut:
    module []rune
}

pub fn build_ast(tokens []SecondTokenizerToken) !FileAST {
    mut file_ast := FileAST{}
    mut i := -1

    for i < tokens.len - 1 {
        i++
        token := tokens[i]
        match true {
            file_ast.module.len == 0 && token.type == .keyword
                && token.value == ?SecondTokenizerValue(Keyword.module) {
                file_ast.module = [`a`]
            }
            file_ast.module.len == 0 {
                return error('Expected `module` keyword at the start of the file, but got `${token.type}`')
            }
            token.type == .keyword && token.value == ?SecondTokenizerValue(Keyword.module) {
                return error('Multiple `module` declarations are not allowed, but got another one')
            }
            token.type == .keyword && token.value == ?SecondTokenizerValue(Keyword.import) {
                dump('import')
            }
            token.type == .newline {
                // ignore newlines
                continue
            }
            else {
                // TODO: turn this into an error after implementing all other AST nodes
                continue
            }
        }
    }

    return file_ast
}

fn test_main() {
    build_ast([]SecondTokenizerToken{}) or { panic(err) }
}