-- This file contains the parser, which converts Nomsu text into abstract syntax trees
lpeg = require 'lpeg'
re = require 're'
lpeg.setmaxstack 10000
{:P,:R,:V,:S,:Cg,:C,:Cp,:B,:Cmt,:Carg} = lpeg
utils = require 'utils'
{:match, :sub, :rep, :gsub, :format, :byte, :match, :find} = string
{:NomsuCode, :LuaCode, :Source} = require "code_obj"
AST = require "nomsu_tree"

NOMSU_DEFS = with {}
    -- Newline supports either windows-style CR+LF or unix-style LF
    .nl = P("\r")^-1 * P("\n")
    .ws = S(" \t")
    .tonumber = tonumber
    string_escapes = n:"\n", t:"\t", b:"\b", a:"\a", v:"\v", f:"\f", r:"\r"
    digit, hex = R('09'), R('09','af','AF')
    .escaped_char = (P("\\")*S("xX")*C(hex*hex)) / => string.char(tonumber(@, 16))
    .escaped_char += (P("\\")*C(digit*(digit^-2))) / => string.char(tonumber @)
    .escaped_char += (P("\\")*C(S("ntbavfr"))) / string_escapes
    .operator_char = S("'`~!@$^&*-+=|<>?/")
    .utf8_char = (
        R("\194\223")*R("\128\191") +
        R("\224\239")*R("\128\191")*R("\128\191") +
        R("\240\244")*R("\128\191")*R("\128\191")*R("\128\191"))
    .ident_char = R("az","AZ","09") + P("_") + .utf8_char

    -- If the line begins with #indent+4 spaces, the pattern matches *those* spaces
    -- and adds them to the current indent (not any more).
    .indent = Cmt Carg(1), (start, userdata)=>
        indented = userdata.indent..'    '
        if sub(@, start, start+#indented-1) == indented
            userdata.indent = indented
            return start + #indented
    -- If the number of leading space characters is <= the number of spaces in the current
    -- indent minus 4, this pattern matches and decrements the current indent exactly once.
    .dedent = Cmt Carg(1), (start, userdata)=>
        dedented = sub(userdata.indent, 1, -5)
        if #match(@, "^[ ]*", start) <= #dedented
            userdata.indent = dedented
            return start
    -- If the number of leading space characters is >= the number of spaces in the current
    -- indent, this pattern matches and does not modify the indent.
    .nodent = Cmt Carg(1), (start, userdata)=>
        if sub(@, start, start+#userdata.indent-1) == userdata.indent
            return start + #userdata.indent

    .userdata = Carg(1)

    .error = (src,end_pos,start_pos,err_msg,userdata)->
        seen_errors = userdata.errors
        if seen_errors[start_pos]
            return true
        if utils.size(seen_errors) >= 10
            seen_errors[start_pos+1] = colored.bright colored.yellow colored.onred "Too many errors, canceling parsing..."
            return #src+1
        err_pos = start_pos
        line_no = pos_to_line(src, err_pos)
        --src = files.read(userdata.source.filename)
        line_starts = LINE_STARTS[src]
        prev_line = line_no == 1 and "" or src\sub(line_starts[line_no-1] or 1, line_starts[line_no]-2)
        err_line = src\sub(line_starts[line_no], (line_starts[line_no+1] or 0)-2)
        next_line = src\sub(line_starts[line_no+1] or -1, (line_starts[line_no+2] or 0)-2)
        i = err_pos-line_starts[line_no]
        pointer = ("-")\rep(i) .. "^"
        err_msg = colored.bright colored.yellow colored.onred (err_msg or "Parse error").." at #{userdata.source.filename}:#{line_no}:"
        if #prev_line > 0 then err_msg ..= "\n"..colored.dim(prev_line)
        err_line = colored.white(err_line\sub(1, i))..colored.bright(colored.red(err_line\sub(i+1,i+1)))..colored.dim(err_line\sub(i+2,-1))
        err_msg ..= "\n#{err_line}\n#{colored.red pointer}"
        if #next_line > 0 then err_msg ..= "\n"..colored.dim(next_line)
        seen_errors[start_pos] = err_msg
        return true

setmetatable(NOMSU_DEFS, {__index:(key)=>
    make_node = (start, value, stop, userdata)->
        if userdata.source
            with userdata.source
                value.source = Source(.filename, .start + start-1, .start + stop-1)
        setmetatable(value, AST[key])
        if value.__init then value\__init!
        for i=1,#value do assert(value[i])
        return value

    self[key] = make_node
    return make_node
})

Parser = {}
NOMSU_PATTERN = do
    -- Just for cleanliness, I put the language spec in its own file using a slightly modified
    -- version of the lpeg.re syntax.
    peg_tidier = re.compile [[
    file <- %nl* version? %nl* {~ (def/comment) (%nl+ (def/comment))* %nl* ~}
    version <- "--" (!"version" [^%nl])* "version" ([ ])* (([0-9])+ -> set_version) ([^%nl])*
    def <- anon_def / captured_def
    anon_def <- ({ident} (" "*) ":"
        {((%nl " "+ [^%nl]*)+) / ([^%nl]*)}) -> "%1 <- %2"
    captured_def <- ({ident} (" "*) "(" {ident} ")" (" "*) ":"
        {((%nl " "+ [^%nl]*)+) / ([^%nl]*)}) -> "%1 <- (({} %3 {} %%userdata) -> %2)"
    ident <- [a-zA-Z_][a-zA-Z0-9_]*
    comment <- "--" [^%nl]*
    ]], {set_version: (v) -> Parser.version = tonumber(v)}
    peg_file = io.open("nomsu.peg")
    if not peg_file and package.nomsupath
        for path in package.nomsupath\gmatch("[^;]+")
            peg_file = io.open(path.."/nomsu.peg")
            break if peg_file
    assert(peg_file, "could not find nomsu.peg file")
    nomsu_peg = peg_tidier\match(peg_file\read('*a'))
    peg_file\close!
    re.compile(nomsu_peg, NOMSU_DEFS)

Parser.parse = (nomsu_code, source=nil)->
    nomsu_code = tostring(nomsu_code)
    userdata = {
        indent: "", errors: {}, :source
    }
    tree = NOMSU_PATTERN\match(nomsu_code, nil, userdata)
    unless tree
        error "In file #{colored.blue tostring(source or "<unknown>")} failed to parse:\n#{colored.onyellow colored.black nomsu_code}"
    if type(tree) == 'number'
        tree = nil

    if next(userdata.errors)
        keys = utils.keys(userdata.errors)
        table.sort(keys)
        errors = [userdata.errors[k] for k in *keys]
        error("Errors occurred while parsing:\n\n"..table.concat(errors, "\n\n"), 0)
    
    return tree

return Parser