import re


class Change:
    """
    Instantiates a string representation of a sound change.
    """

    def __init__(self, change):
        self.parse(change)

    def __repr__(self):
        return f"{self.b}>{self.a}/{self.f}_{self.t}"

    def parse(self, change):
        if '/' in change:
            _change, _env = change.split('/')
        else:
            _change = change
            _env = '_'
        self.b, self.a = _change.split('>')
        self.f, self.t = _env.split('_')
        
        if self.f.startswith("{") and self.f.endswith("}"):
            self.f = self.f[1:-1].split(',')
            self.f = f"[{''.join(self.f)}]"
        if self.t.startswith("{") and self.t.endswith("}"):
            self.t = self.t[1:-1].split(',')
            self.t = f"[{''.join(self.t)}]"

    def sub(self, string):
        return re.sub(f"(?<={self.f}){self.b}(?={self.t})", f"{self.a}", f"#{string}#").strip('#')