import run_tests
from typing import Dict, Optional

class ParseTOML:
    def __init__( self, toml: str ) -> None:
        self.text = toml
        self.idx = 0
        self.sec : Section = {}
        self.key = ''
        self.parsed : TOML = {}
        self.error = False
        self.top()

    def eof( self ) -> bool:
        return self.error or self.idx >= len( self.text )

    def peek( self ) -> str:
        if self.eof():
            return ''
        else:
            return self.text[ self.idx ]

    def shift( self ) -> str:
        x = self.peek()
        self.idx += 1
        return x

    def require( self, x: str ) -> None:
        if self.shift() != x:
            self.error = True

    def top( self ) -> None:
        while not self.eof():
            self.line()

    def line( self ) -> None:
        if self.peek() == '[':
            self.header()
        else:
            self.kvpair()

        self.require( '\n' )

    def header( self ) -> None:
        self.parsed[ self.key ] = self.sec
        self.sec = {}
        self.require( '[' )
        self.key = self.word()
        self.require( ']' )

    def kvpair( self ) -> None:
        k = self.word()
        self.require( '=' )
        v = self.word()
        self.sec[ k ] = v

    def word( self ) -> str:
        x = self.shift()

        if not x.isalpha():
            self.error = True

        while self.peek().isalnum():
            x += self.shift()

        return x

    def get( self ) -> Optional[ TOML ]:
        self.parsed[ self.key ] = self.sec
        return None if self.error else self.parsed


def parse_toml( toml: str ) -> Optional[ TOML ]:
    return ParseTOML( toml ).get()