require "colorize"
require "readline"

require "./reader"
require "./printer"
require "./types"
require "./env"
require "./core"
require "./error"

# Note:
# Employed downcase names because Crystal prohibits uppercase names for methods

module Crisp
  extend self

  def func_of(env, binds, body)
    -> (args : Array(Crisp::Type)) {
      new_env = Crisp::Env.new(env, binds, args)
      eval(body, new_env)
    } as Crisp::Func
  end

  def eval_ast(ast, env)
    return ast.map{|n| eval(n, env) as Crisp::Type} if ast.is_a? Array

    val = ast.unwrap

    Crisp::Type.new case val
    when Crisp::Symbol
      if e = env.get(val.str)
        e
      else
        eval_error "'#{val.str}' not found"
      end
    when Crisp::List
      val.each_with_object(Crisp::List.new){|n, l| l << eval(n, env)}
    when Crisp::Vector
      val.each_with_object(Crisp::Vector.new){|n, l| l << eval(n, env)}
    when Crisp::HashMap
      new_map = Crisp::HashMap.new
      val.each{|k, v| new_map[k] = eval(v, env)}
      new_map
    else
      val
    end
  end

  def read(str)
    read_str str
  end

  macro pair?(list)
    {{list}}.is_a?(Array) && !{{list}}.empty?
  end

  def quasiquote(ast)
    list = ast.unwrap

    unless pair?(list)
      return Crisp::Type.new(
        Crisp::List.new << gen_type(Crisp::Symbol, "quote") << ast
      )
    end

    head = list.first.unwrap

    case
    # ("unquote" ...)
    when head.is_a?(Crisp::Symbol) && head.str == "unquote"
      list[1]
    # (("splice-unquote" ...) ...)
    when pair?(head) && (arg0 = head.first.unwrap).is_a?(Crisp::Symbol) && arg0.str == "splice-unquote"
      tail = Crisp::Type.new list[1..-1].to_crisp_value
      Crisp::Type.new(
        Crisp::List.new << gen_type(Crisp::Symbol, "concat") << head[1] << quasiquote(tail)
      )
    else
      tail = Crisp::Type.new list[1..-1].to_crisp_value
      Crisp::Type.new(
        Crisp::List.new << gen_type(Crisp::Symbol, "cons") << quasiquote(list.first) << quasiquote(tail)
      )
    end
  end

  def macro_call?(ast, env)
    list = ast.unwrap
    return false unless list.is_a? Crisp::List
    return false if list.empty?

    sym = list.first.unwrap
    return false unless sym.is_a? Crisp::Symbol

    func = env.find(sym.str).try(&.data[sym.str])
    return false unless func && func.macro?

    true
  end

  def macroexpand(ast, env)
    while macro_call?(ast, env)

      # Already checked in macro_call?
      list = ast.unwrap as Crisp::List
      func_sym = list[0].unwrap as Crisp::Symbol
      func = env.get(func_sym.str).unwrap

      case func
      when Crisp::Func
        ast = func.call(list[1..-1])
      when Crisp::Closure
        ast = func.fn.call(list[1..-1])
      else
        eval_error "macro '#{func_sym.str}' must be function: #{ast}"
      end
    end

    ast
  end

  macro invoke_list(l, env)
    f = eval({{l}}.first, {{env}}).unwrap
    args = eval_ast({{l}}[1..-1], {{env}}) as Array

    case f
    when Crisp::Closure
      ast = f.ast
      {{env}} = Crisp::Env.new(f.env, f.params, args)
      next # TCO
    when Crisp::Func
      return f.call args
    else
      eval_error "expected function as the first argument: #{f}"
    end
  end

  def debug(ast)
    puts print(ast).colorize.red
  end

  def eval(ast, env)
    # 'next' in 'do...end' has a bug in crystal 0.7.1
    # https://github.com/manastech/crystal/issues/659
    while true
      return eval_ast(ast, env) unless ast.unwrap.is_a? Crisp::List

      ast = macroexpand(ast, env)

      list = ast.unwrap

      return ast unless list.is_a? Crisp::List
      return ast if list.empty?

      head = list.first.unwrap

      return invoke_list(list, env) unless head.is_a? Crisp::Symbol

      return Crisp::Type.new case head.str
        when "def!"
          eval_error "wrong number of argument for 'def!'" unless list.size == 3
          a1 = list[1].unwrap
          eval_error "1st argument of 'def!' must be symbol: #{a1}" unless a1.is_a? Crisp::Symbol
          env.set(a1.str, eval(list[2], env))
        when "let*"
          eval_error "wrong number of argument for 'def!'" unless list.size == 3

          bindings = list[1].unwrap
          eval_error "1st argument of 'let*' must be list or vector" unless bindings.is_a? Array
          eval_error "size of binding list must be even" unless bindings.size.even?

          new_env = Crisp::Env.new env
          bindings.each_slice(2) do |binding|
            key, value = binding
            name = key.unwrap
            eval_error "name of binding must be specified as symbol #{name}" unless name.is_a? Crisp::Symbol
            new_env.set(name.str, eval(value, new_env))
          end

          ast, env = list[2], new_env
          next # TCO
        when "do"
          if list.empty?
            ast = Crisp::Type.new nil
            next
          end

          eval_ast(list[1..-2].to_crisp_value, env)
          ast = list.last
          next # TCO
        when "if"
          ast = unless eval(list[1], env).unwrap
            list.size >= 4 ? list[3] : Crisp::Type.new(nil)
          else
            list[2]
          end
          next # TCO
        when "fn*"
          params = list[1].unwrap
          unless params.is_a? Array
            eval_error "'fn*' parameters must be list or vector: #{params}"
          end
          Crisp::Closure.new(list[2], params, env, func_of(env, params, list[2]))
        when "quote"
          list[1]
        when "quasiquote"
          ast = quasiquote list[1]
          next # TCO
        when "defmacro!"
          eval_error "wrong number of argument for 'defmacro!'" unless list.size == 3
          a1 = list[1].unwrap
          eval_error "1st argument of 'defmacro!' must be symbol: #{a1}" unless a1.is_a? Crisp::Symbol
          env.set(a1.str, eval(list[2], env).tap{|n| n.is_macro = true})
        when "macroexpand"
          macroexpand(list[1], env)
        when "try*"
          catch_list = list[2].unwrap
          return eval(list[1], env) unless catch_list.is_a? Crisp::List

          catch_head = catch_list.first.unwrap
          return eval(list[1], env) unless catch_head.is_a? Crisp::Symbol
          return eval(list[1], env) unless catch_head.str == "catch*"

          begin
            eval(list[1], env)
          rescue e : Crisp::RuntimeException
            new_env = Crisp::Env.new(env, [catch_list[1]], [e.thrown])
            eval(catch_list[2], new_env)
          rescue e
            new_env = Crisp::Env.new(env, [catch_list[1]], [Crisp::Type.new e.message])
            eval(catch_list[2], new_env)
          end
        else
          invoke_list(list, env)
        end
    end
  end

  def print(result)
    pr_str(result, true)
  end

  def rep(str)
    print(eval(read(str), $repl_env))
  end

  class ProgramState
    def rep(str)
      print(eval(read(str), @env))
    end

    def initialize(args)
      @env = Crisp::Env.new nil

      Crisp::NameSpace.each{|k,v| @curent_env.set(k, Crisp::Type.new(v))}

      @env.set("eval", Crisp::Type.new -> (args: Array(Crisp::Type)){ Crisp.eval(args[0], @env) })

      rep "(def! not (fn* (a) (if a false true)))"
      rep "(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))"
      rep "(defmacro! cond (fn* (& xs) (if (> (count xs) 0) (list 'if (first xs) (if (> (count xs) 1) (nth xs 1) (throw \"odd number of forms to cond\")) (cons 'cond (rest (rest xs)))))))"
      rep "(defmacro! or (fn* (& xs) (if (empty? xs) nil (if (= 1 (count xs)) (first xs) `(let* (or_FIXME ~(first xs)) (if or_FIXME or_FIXME (or ~@(rest xs))))))))"
      rep "(def! *host-language* \"crystal\")"

      argv = Crisp::List.new

      if args
        args.each do |a|
          argv << Crisp::Type.new a
        end
      end

      @env.set("*ARGV*", Crisp::Type.new argv)
    end
  end

  class Interpreter
    def initialize(args)
      @state = ProgramState.new args
    end

    def run(filename = nil)
      if filename
        begin
          Crisp.rep "(load-file \"#{filename}\")"
        rescue e
          STDERR.puts e
          exit 1
        end

        exit
      end

      while line = Readline.readline("Crisp> ", true)
        begin
          puts @state.rep(line)
        rescue e
          STDERR.puts e
        end
      end
    end
  end
end