require "readline"
require "types"
require "reader"
require "printer"
require "env"

# read
def READ(str)
    return read_str(str)
end

# eval
def eval_ast(ast, env)
    return case ast
        when Symbol
            env.get(ast)
        when List   
            List.new ast.map{|a| EVAL(a, env)}
        when Vector
            Vector.new ast.map{|a| EVAL(a, env)}
        else 
            ast
    end
end

def EVAL(ast, env)
    if not ast.is_a? List
        return eval_ast(ast, env)
    end

    # apply list
    a0,a1,a2,a3 = ast
    case a0
    when :def!
        return env.set(a1, EVAL(a2, env))
    when :"let*"
        let_env = Env.new(env)
        a1.each_slice(2) do |a,e|
            let_env.set(a, EVAL(e, let_env))
        end
        return EVAL(a2, let_env)
    else
        el = eval_ast(ast, env)
        f = el[0]
        return f[*el.drop(1)]
    end
end

# print
def PRINT(exp)
    return _pr_str(exp, true)
end

# repl
repl_env = Env.new
REP = lambda {|str| PRINT(EVAL(READ(str), repl_env)) }
_ref = lambda {|k,v| repl_env.set(k, v) }

_ref[:+, lambda {|a,b| a + b}]
_ref[:-, lambda {|a,b| a - b}]
_ref[:*, lambda {|a,b| a * b}]
_ref[:/, lambda {|a,b| a / b}]

while line = Readline.readline("user> ", true)
    begin
        puts REP[line]
    rescue Exception => e
        puts "Error: #{e}" 
        puts "\t#{e.backtrace.join("\n\t")}"
    end
end