------------------------------------------------------------------------------
-- Copyright (c) 2006-2013 Fabien Fleutot and others.
--
-- All rights reserved.
--
-- This program and the accompanying materials are made available
-- under the terms of the Eclipse Public License v1.0 which
-- accompanies this distribution, and is available at
-- http://www.eclipse.org/legal/epl-v10.html
--
-- This program and the accompanying materials are also made available
-- under the terms of the MIT public license which accompanies this
-- distribution, and is available at http://www.lua.org/license.html
--
-- Contributors:
--     Fabien Fleutot - API and implementation
--
-------------------------------------------------------------------------------

-------------------------------------------------------------------------------
--
-- Summary: metalua parser, statement/block parser. This is part of the
-- definition of module [mlp].
--
-------------------------------------------------------------------------------

-------------------------------------------------------------------------------
--
-- Exports API:
-- * [mlp.stat()]
-- * [mlp.block()]
-- * [mlp.for_header()]
--
-------------------------------------------------------------------------------

local lexer    = require 'metalua.grammar.lexer'
local gg       = require 'metalua.grammar.generator'

local annot = require 'metalua.compiler.parser.annot.generator'

--------------------------------------------------------------------------------
-- List of all keywords that indicate the end of a statement block. Users are
-- likely to extend this list when designing extensions.
--------------------------------------------------------------------------------


return function(M)
  local _M = gg.future(M)

  M.block_terminators = { "else", "elseif", "end", "until", ")", "}", "]" }

  -- FIXME: this must be handled from within GG!!!
  -- FIXME: there's no :add method in the list anyway. Added by gg.list?!
  function M.block_terminators :add(x)
    if type (x) == "table" then for _, y in ipairs(x) do self :add (y) end
    else table.insert (self, x) end
  end

  ----------------------------------------------------------------------------
  -- list of statements, possibly followed by semicolons
  ----------------------------------------------------------------------------
  M.block = gg.list {
    name        = "statements block",
    terminators = M.block_terminators,
    primary     = function (lx)
      -- FIXME use gg.optkeyword()
      local x = M.stat (lx)
      if lx:is_keyword (lx:peek(), ";") then lx:next() end
      return x
    end }

  ----------------------------------------------------------------------------
  -- Helper function for "return <expr_list>" parsing.
  -- Called when parsing return statements.
  -- The specific test for initial ";" is because it's not a block terminator,
  -- so without it gg.list would choke on "return ;" statements.
  -- We don't make a modified copy of block_terminators because this list
  -- is sometimes modified at runtime, and the return parser would get out of
  -- sync if it was relying on a copy.
  ----------------------------------------------------------------------------
  local return_expr_list_parser = gg.multisequence{
    { ";" , builder = function() return { } end },
    default = gg.list {
      _M.expr, separators = ",", terminators = M.block_terminators } }


  local for_vars_list = gg.list{
    name        = "for variables list",
    primary     = _M.id,
    separators  = ",",
    terminators = "in" }

  ----------------------------------------------------------------------------
  -- for header, between [for] and [do] (exclusive).
  -- Return the `Forxxx{...} AST, without the body element (the last one).
  ----------------------------------------------------------------------------
  function M.for_header (lx)
    local vars = M.id_list(lx)
    if lx :is_keyword (lx:peek(), "=") then
      if #vars ~= 1 then
        gg.parse_error (lx, "numeric for only accepts one variable")
      end
      lx:next() -- skip "="
      local exprs = M.expr_list (lx)
      if #exprs < 2 or #exprs > 3 then
        gg.parse_error (lx, "numeric for requires 2 or 3 boundaries")
      end
      return { tag="Fornum", vars[1], unpack (exprs) }
    else
      if not lx :is_keyword (lx :next(), "in") then
        gg.parse_error (lx, '"=" or "in" expected in for loop')
      end
      local exprs = M.expr_list (lx)
      return { tag="Forin", vars, exprs }
    end
  end

  ----------------------------------------------------------------------------
  -- Function def parser helper: id ( . id ) *
  ----------------------------------------------------------------------------
  local function fn_builder (list)
    local acc = list[1]
    local first = acc.lineinfo.first
    for i = 2, #list do
      local index = M.id2string(list[i])
      local li = lexer.new_lineinfo(first, index.lineinfo.last)
      acc = { tag="Index", acc, index, lineinfo=li }
    end
    return acc
  end
  local func_name = gg.list{ _M.id, separators = ".", builder = fn_builder }

  ----------------------------------------------------------------------------
  -- Function def parser helper: ( : id )?
  ----------------------------------------------------------------------------
  local method_name = gg.onkeyword{ name = "method invocation", ":", _M.id,
    transformers = { function(x) return x and x.tag=='Id' and M.id2string(x) end } }

  ----------------------------------------------------------------------------
  -- Function def builder
  ----------------------------------------------------------------------------
  local function funcdef_builder(x)
    local name, method, func = unpack(x)
    if method then
      name = { tag="Index", name, method,
        lineinfo = {
          first = name.lineinfo.first,
          last  = method.lineinfo.last } }
      table.insert (func[1], 1, {tag="Id", "self"})
    end
    local r = { tag="Set", {name}, {func} }
    r[1].lineinfo = name.lineinfo
    r[2].lineinfo = func.lineinfo
    return r
  end


  ----------------------------------------------------------------------------
  -- if statement builder
  ----------------------------------------------------------------------------
  local function if_builder (x)
    local cond_block_pairs, else_block, r = x[1], x[2], {tag="If"}
    local n_pairs = #cond_block_pairs
    for i = 1, n_pairs do
      local cond, block = unpack(cond_block_pairs[i])
      r[2*i-1], r[2*i] = cond, block
    end
    if else_block then table.insert(r, #r+1, else_block) end
    return r
  end

  --------------------------------------------------------------------------------
  -- produce a list of (expr,block) pairs
  --------------------------------------------------------------------------------
  local elseifs_parser = gg.list {
    gg.sequence { _M.expr, "then", _M.block , name='elseif parser' },
    separators  = "elseif",
    terminators = { "else", "end" }
  }

  local annot_expr = gg.sequence {
    _M.expr,
    gg.onkeyword{ "#", gg.future(M, 'annot').tf },
    builder = function(x)
      local e, a = unpack(x)
      if a then return { tag='Annot', e, a }
      else return e end
    end }

  local annot_expr_list = gg.list {
    primary = annot.opt(M, _M.expr, 'tf'), separators = ',' }

  ------------------------------------------------------------------------
  -- assignments and calls: statements that don't start with a keyword
  ------------------------------------------------------------------------
  local function assign_or_call_stat_parser (lx)
    local e = annot_expr_list (lx)
    local a = lx:is_keyword(lx:peek())
    local op = a and M.assignments[a]
    -- TODO: refactor annotations
    if op then
      --FIXME: check that [e] is a LHS
      lx :next()
      local annots
      e, annots = annot.split(e)
      local v = M.expr_list (lx)
      if type(op)=="string" then return { tag=op, e, v, annots }
      else return op (e, v) end
    else
      assert (#e > 0)
      if #e > 1 then
        gg.parse_error (lx,
          "comma is not a valid statement separator; statement can be "..
          "separated by semicolons, or not separated at all")
      elseif e[1].tag ~= "Call" and e[1].tag ~= "Invoke" then
        local typename
        if e[1].tag == 'Id' then
          typename = '("'..e[1][1]..'") is an identifier'
        elseif e[1].tag == 'Op' then
          typename = "is an arithmetic operation"
        else typename = "is of type '"..(e[1].tag or "<list>").."'" end
        gg.parse_error (lx,
          "This expression %s; "..
          "a statement was expected, and only function and method call "..
          "expressions can be used as statements", typename);
      end
      return e[1]
    end
  end

  M.local_stat_parser = gg.multisequence{
    -- local function <name> <func_val>
    { "function", _M.id, _M.func_val, builder =
      function(x)
        local vars = { x[1], lineinfo = x[1].lineinfo }
        local vals = { x[2], lineinfo = x[2].lineinfo }
        return { tag="Localrec", vars, vals }
      end },
    -- local <id_list> ( = <expr_list> )?
    default = gg.sequence{
      gg.list{
        primary = annot.opt(M, _M.id, 'tf'),
        separators = ',' },
      gg.onkeyword{ "=", _M.expr_list },
      builder = function(x)
        local annotated_left, right = unpack(x)
        local left, annotations = annot.split(annotated_left)
        return {tag="Local", left, right or { }, annotations }
      end } }

  ------------------------------------------------------------------------
  -- statement
  ------------------------------------------------------------------------
  M.stat = gg.multisequence {
    name = "statement",
    { "do", _M.block, "end", builder =
      function (x) return { tag="Do", unpack (x[1]) } end },
    { "for", _M.for_header, "do", _M.block, "end", builder =
      function (x) x[1][#x[1]+1] = x[2]; return x[1] end },
    { "function", func_name, method_name, _M.func_val, builder=funcdef_builder },
    { "while", _M.expr, "do", _M.block, "end", builder = "While" },
    { "repeat", _M.block, "until", _M.expr, builder = "Repeat" },
    { "goto", _M.id, builder = function(x) return {tag='Goto',x[1]} end },
    { "::",_M.id,"::", builder = function(x) return {tag='Label',x[1]} end },
    { "local", _M.local_stat_parser, builder = unpack },
    { "return", return_expr_list_parser, builder =
      function(x) x[1].tag='Return'; return x[1] end },
    { "break", builder = function() return { tag="Break" } end },
    { "-{", gg.future(M, 'meta').splice_content, "}", builder = unpack },
    { "if", gg.nonempty(elseifs_parser), gg.onkeyword{ "else", M.block }, "end",
      builder = if_builder },
    default = assign_or_call_stat_parser }

  M.assignments = {
    ["="] = "Set"
  }

  function M.assignments:add(k, v) self[k] = v end

  return M
end