pragma solidity >=0.8.0;
/// SPDX-License-Identifier: MIT
/*
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⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠿⠿⠛⢉⣉⣉⣉⣉⣉⣉⣉⠙⠛⠿⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠟⢉⣁⣴⣶⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣶⣶⣤⣉⠛⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠟⠉⣠⣶⣿⣿⣿⣿⣿⣿⡿⠿⢿⣛⣛⣛⡛⠿⠿⣿⣿⠟⣩⡙⢦⣌⠻⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠋⢀⣴⣿⣿⣿⣿⣿⣿⡿⢛⣩⡶⠿⠿⠿⠿⣿⣿⣿⣶⣶⡍⣼⣿⣿⣆⠻⣷⣄⠙⠿⠿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡟⢁⣴⣿⣿⣿⣿⣿⣿⠿⢋⣀⣭⣶⣶⣶⣿⣷⣶⣶⣦⣭⣙⡻⢠⣿⣿⣟⠛⢀⣦⢉⣡⣶⣄⡘⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡟⢀⣾⣿⣿⣿⣿⡿⢟⣡⣶⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⢸⣿⣿⣿⣿⡀⣿⢃⣉⣻⡿⡇⢹⣿⣿⣿⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡟⢀⣿⣿⣿⣿⣿⠏⣴⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣄⣙⣛⣛⣋⡄⣁⠺⣿⣿⡿⢠⣦⡙⢿⣿⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠀⣾⣿⣿⣿⣿⣿⣾⣿⣿⣿⣿⣿⠿⠿⠿⠿⠿⠿⠿⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠟⡁⢻⣷⣌⣛⣡⣬⡹⢿⡆⢻⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠟⠃⣼⣿⣿⣿⣿⣿⣿⣿⣿⡿⢋⣭⡶⠖⣉⣴⣶⣶⣶⣶⣶⣶⣦⣭⣭⣭⣭⣭⣭⣴⣾⣿⡌⢿⣿⣿⣿⣿⣿⣦⠁⢸⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠋⣡⣴⣿⠀⣿⣿⣿⣿⣿⣿⣿⡿⢋⣴⣿⠋⣴⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣦⡙⢿⣿⣿⣿⣿⣷⡈⢿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡟⢁⣾⣿⣿⣿⢰⣿⣿⣿⣿⣿⣿⣟⣡⣿⡿⢁⣾⣿⣿⣿⣿⠿⠿⣛⠻⠿⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣦⡙⢿⣿⣿⣿⣷⡈⢿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⢃⣾⣿⣿⣿⣿⣈⣿⣿⣿⣿⣿⣿⣿⣿⣿⠁⣼⣿⣿⣿⣿⣇⠖⣿⣿⣿⣷⣦⣉⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣦⡙⣿⣿⣿⠃⢸⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣿⣿⣿⡇⢸⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠀⣿⣿⣿⠟⢻⠉⠄⠹⠿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⣿⣿⣿⣿⣿⡇⢸⣿⣿⡇⢸⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣿⣿⣿⡇⢸⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠀⣿⣿⣿⣷⠀ cum⠀⠀⠈⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡁⣈⠙⢿⣿⣿⢃⣾⣿⣿⠇⣼⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⡿⠛⢉⣠⠀⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠀⣿⣿⣿⣿⣄⠠⢀⡀⣠⠇⠸⣿⣿⣿⣿⣿⣿⣿⣿⠿⢿⣟⠟⢻⣧⢸⠟⣡⣾⣿⡟⢁⣼⣿⣿⣿⣿⣿
⣿⣿⣿⣿⠟⢉⣠⣶⣿⣿⣇⠘⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠀⢸⣿⣿⣿⣿⣷⣶⣬⣭⣥⣼⣿⣿⣿⣿⣿⣿⡿⠃⠀⠠⠀⡈⠉⠅⢠⣾⠿⠟⣩⣴⣿⣿⣿⣿⣿⣿⣿
⣿⣿⠟⢁⣴⣾⣿⣿⣿⣿⣿⣆⠘⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠀⠟⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡅⠀⣐⣚⡸⠁⠂⣰⡍⢡⣤⣈⠻⢿⣿⣿⣿⣿⣿⣿⣿
⡟⠁⣰⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⡈⠻⣿⣿⣿⣿⣿⣿⣿⣿⣿⠟⢁⣼⣶⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣶⣶⣶⣶⣾⢸⣿⡇⢸⣿⣿⣷⣄⠙⢿⣿⣿⣿⣿⣿
⡇⠸⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣧⠐⣤⣍⣹⣿⣿⣿⠿⢋⣡⣴⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣉⡙⢿⡿⢁⣿⣿⣿⣿⣿⡟⢸⣿⣧⢸⣿⣿⣿⣿⣷⡌⢻⣿⣿⣿⣿
⣧⡀⠸⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣧⠘⢿⣿⣿⣿⣿⡇⣿⣿⣋⢻⣿⣿⣿⣿⣿⣿⣿⡉⡛⢛⣛⣛⡻⢿⣿⣿⣶⣾⣿⣿⣿⣿⣿⡇⣸⣿⣿⠈⣿⣿⣿⣿⣿⣷⡈⣿⣿⣿⣿
⣿⣧⣀⠢⣌⣉⠙⠛⠿⠿⣿⣿⣿⣿⣿⣷⣌⠻⣿⣿⣿⡇⣿⣿⣿⡄⢿⣿⣿⣿⣿⣿⣿⣷⠙⣄⡲⣦⣍⡒⠭⠍⢿⣿⣿⣿⣿⣿⡟⢠⣿⣿⡟⢰⣿⣿⣿⣿⣿⡿⠃⣿⣿⣿⣿
⣿⣿⣿⣷⣌⠙⠿⣷⢶⣤⣄⣉⠙⠻⠿⣿⣿⣷⣦⣍⣛⠃⣿⣿⣿⣿⣌⠻⣿⣿⣿⣿⣿⣿⣷⣈⠿⣮⣭⡵⢂⣾⣿⣿⣿⣿⡿⢋⣴⣿⣿⠟⣠⣾⣿⣿⣿⣿⡿⠃⢠⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣦⣌⠙⠿⣿⣿⣿⣷⣦⣄⠉⠻⣿⣿⣿⠀⣿⣿⣿⣿⣿⣦⡙⢿⣿⣿⣿⣿⣿⣿⣶⣭⣭⣵⣿⣿⣿⠿⠟⠩⠴⠿⠟⣋⣡⣾⣿⣿⣿⣿⠟⠋⣀⣴⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣿⣿⣿⣦⣌⠻⣿⣿⣿⣿⣷⣄⠘⣿⠏⣰⣿⣿⣿⣿⣿⣿⣿⣶⣉⡻⠿⣿⣿⣿⣿⣿⣿⡿⢟⣡⣶⣶⣶⣶⣶⣶⣿⣿⣿⣿⣿⡿⠛⢁⣤⣾⣿⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⡌⠻⣿⣿⣿⣿⣆⠘⢰⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣶⣬⣉⣛⠿⣛⣉⣴⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡟⠋⣠⣾⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣆⠘⣿⣿⣿⣿⣦⠘⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣶⣬⣉⡙⠻⢿⣿⣿⣿⣿⣿⣿⣿⣿⠟⢠⣾⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠿⢛⣋⣉⣁⣈⠻⣿⣿⣿⣷⡀⠻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⣦⣌⡙⠻⢿⣿⣿⣿⡏⢀⣉⡛⠿⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣿⡿⢋⣴⣾⣿⣿⣿⣿⣿⣷⣄⠙⠻⠿⣷⡀⠻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⣦⡉⠿⠿⢠⣾⣿⣿⣷⣄⠙⣿⣿⣿⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⡿⠋⣠⣾⣿⣿⣿⣿⣿⣿⡿⣿⣿⣷⡙⣶⣌⡛⢀⠹⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣆⠀⡘⢿⣿⡿⢿⣿⣷⡈⢿⣿⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⡿⠁⣴⣿⣿⣿⣿⣿⣿⣿⣿⡇⣌⡛⠿⣷⣌⠻⣿⣦⣀⠈⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡆⣰⡘⣿⣿⡌⠛⢿⣧⡀⢿⣿⣿⣿⣿⣿⣿
⣿⣿⣿⣿⠇⣸⣿⢇⠹⣿⣿⣿⣿⣿⣿⣷⠸⣿⣷⣌⡻⢷⣌⠻⣿⣷⣄⠙⠿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⢁⣿⣧⠘⣿⣿⡔⢦⡙⢿⣦⣌⠹⢿⣿⣿⣿
⣿⣿⣿⡏⢰⣿⡏⣸⣧⡹⣿⣿⣿⣿⣿⣿⣧⡙⢿⣿⣿⣦⠹⣷⣦⣙⠻⣿⣦⣉⡛⠿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠿⠟⣉⣴⣿⣿⣿⡇⢸⣿⣷⡸⣿⣦⡙⢿⣷⣌⠹⢿⣿
⣿⣿⣿⡇⣸⣿⡇⣿⣿⣷⣌⢻⣿⣿⣿⣿⣿⣿⣶⣝⠻⣿⣧⢹⣿⣿⣦⠙⣿⣿⣿⣶⣶⣭⣍⣉⣉⣉⣉⣉⣩⣭⣴⣶⣶⣿⣿⣿⣿⣿⣿⣿⡆⢿⣿⣇⢹⣿⣿⣆⢹⣿⣧⡈⢻
⣿⣿⣿⠁⣿⣿⡇⣿⣿⣿⣿⣆⢻⣿⣿⣿⣿⣿⣿⣿⣷⡌⣿⢀⣿⣿⣿⣷⠙⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡇⢸⣿⣿⡆⢿⣿⣿⡎⣿⣿⣷⡈
⣿⣿⡏⡀⣿⣿⡇⢹⣿⣿⣿⣿⡎⣿⣿⣿⣿⣿⣿⣿⣿⣿⢀⣾⣿⢻⣿⣿⡄⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⢸⣿⣿⣿⣆⡻⠿⣣⣿⣿⣿⣇
⣿⣿⣿⠇⢹⣿⣿⣌⠻⣿⣿⡿⢁⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⢃⣿⣿⣿⠇⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠀⠻⢿⣿⣿⣿⣿⣿⣿⣿⣿⡿
⣿⣿⡿⢰⡆⢹⣿⣿⣷⣬⣭⣴⣿⣿⣿⣿⣿⠿⢟⣛⣋⣉⣉⠰⣿⣿⣿⡿⠀⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⢀⣿⣶⣬⡙⢿⣿⣿⣿⣿⣿⡇
⣿⣿⣇⠸⣷⡐⣿⣿⣿⣿⣿⣿⣿⣿⡿⢋⣴⣾⡿⠿⠿⠿⢿⣷⡘⣿⡿⢀⣾⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡇⢠⣦⣭⣙⠿⣦⢹⣿⣿⣿⡟⢰
⣿⣿⣿⡆⠹⠇⣸⣿⣿⣿⣌⣉⢉⣥⣶⡿⢋⣭⣶⣾⣿⣷⣶⣌⠃⢋⣴⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠃⣾⣿⣿⣿⣷⡌⢸⣿⣿⠏⣰⣿
⣿⣿⣿⣷⡀⠺⣿⣿⣿⣿⣿⡇⢸⡿⢋⣴⣿⣿⣿⣿⣿⣿⣿⣿⣷⡘⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡏⢸⣿⣿⣿⣿⣿⣿⠸⠟⣡⣾⣿⣿
⣿⣿⣿⣿⣷⣄⠙⢿⣿⣿⣿⣧⠸⢃⣾⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⠘⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠃⣾⣿⣿⣿⣿⣿⣿⠀⣿⣿⣿⣿⣿
⣿⣿⣿⣿⣿⣿⣷⣄⣉⣉⣛⣋⣡⠸⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣧⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡏⢸⣿⣿⣿⣿⣿⣿⣿⡆⢸⣿⣿⣿⣿
*/
abstract contract ERC20 {
    /*//////////////////////////////////////////////////////////////
                                 EVENTS
    //////////////////////////////////////////////////////////////*/

    event Transfer(address indexed from, address indexed to, uint256 amount);

    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 amount
    );

    /*//////////////////////////////////////////////////////////////
                            METADATA STORAGE
    //////////////////////////////////////////////////////////////*/

    string public name;

    string public symbol;

    uint8 public immutable decimals;

    /*//////////////////////////////////////////////////////////////
                              ERC20 STORAGE
    //////////////////////////////////////////////////////////////*/

    uint256 public totalSupply;

    mapping(address => uint256) public balanceOf;

    mapping(address => mapping(address => uint256)) public allowance;

    /*//////////////////////////////////////////////////////////////
                            EIP-2612 STORAGE
    //////////////////////////////////////////////////////////////*/

    uint256 internal immutable INITIAL_CHAIN_ID;

    bytes32 internal immutable INITIAL_DOMAIN_SEPARATOR;

    mapping(address => uint256) public nonces;

    /*//////////////////////////////////////////////////////////////
                               CONSTRUCTOR
    //////////////////////////////////////////////////////////////*/

    constructor(string memory _name, string memory _symbol, uint8 _decimals) {
        name = _name;
        symbol = _symbol;
        decimals = _decimals;

        INITIAL_CHAIN_ID = block.chainid;
        INITIAL_DOMAIN_SEPARATOR = computeDomainSeparator();
    }

    /*//////////////////////////////////////////////////////////////
                               ERC20 LOGIC
    //////////////////////////////////////////////////////////////*/

    function approve(
        address spender,
        uint256 amount
    ) public virtual returns (bool) {
        allowance[msg.sender][spender] = amount;

        emit Approval(msg.sender, spender, amount);

        return true;
    }

    function transfer(
        address to,
        uint256 amount
    ) public virtual returns (bool) {
        balanceOf[msg.sender] -= amount;

        // Cannot overflow because the sum of all user
        // balances can't exceed the max uint256 value.
        unchecked {
            balanceOf[to] += amount;
        }

        emit Transfer(msg.sender, to, amount);

        return true;
    }

    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) public virtual returns (bool) {
        uint256 allowed = allowance[from][msg.sender]; // Saves gas for limited approvals.

        if (allowed != type(uint256).max)
            allowance[from][msg.sender] = allowed - amount;

        balanceOf[from] -= amount;

        // Cannot overflow because the sum of all user
        // balances can't exceed the max uint256 value.
        unchecked {
            balanceOf[to] += amount;
        }

        emit Transfer(from, to, amount);

        return true;
    }

    /*//////////////////////////////////////////////////////////////
                             EIP-2612 LOGIC
    //////////////////////////////////////////////////////////////*/

    function permit(
        address owner,
        address spender,
        uint256 value,
        uint256 deadline,
        uint8 v,
        bytes32 r,
        bytes32 s
    ) public virtual {
        require(deadline >= block.timestamp, "PERMIT_DEADLINE_EXPIRED");

        // Unchecked because the only math done is incrementing
        // the owner's nonce which cannot realistically overflow.
        unchecked {
            address recoveredAddress = ecrecover(
                keccak256(
                    abi.encodePacked(
                        "\x19\x01",
                        DOMAIN_SEPARATOR(),
                        keccak256(
                            abi.encode(
                                keccak256(
                                    "Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)"
                                ),
                                owner,
                                spender,
                                value,
                                nonces[owner]++,
                                deadline
                            )
                        )
                    )
                ),
                v,
                r,
                s
            );

            require(
                recoveredAddress != address(0) && recoveredAddress == owner,
                "INVALID_SIGNER"
            );

            allowance[recoveredAddress][spender] = value;
        }

        emit Approval(owner, spender, value);
    }

    function DOMAIN_SEPARATOR() public view virtual returns (bytes32) {
        return
            block.chainid == INITIAL_CHAIN_ID
                ? INITIAL_DOMAIN_SEPARATOR
                : computeDomainSeparator();
    }

    function computeDomainSeparator() internal view virtual returns (bytes32) {
        return
            keccak256(
                abi.encode(
                    keccak256(
                        "EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"
                    ),
                    keccak256(bytes(name)),
                    keccak256("1"),
                    block.chainid,
                    address(this)
                )
            );
    }

    /*//////////////////////////////////////////////////////////////
                        INTERNAL MINT/BURN LOGIC
    //////////////////////////////////////////////////////////////*/

    function _mint(address to, uint256 amount) internal virtual {
        totalSupply += amount;

        // Cannot overflow because the sum of all user
        // balances can't exceed the max uint256 value.
        unchecked {
            balanceOf[to] += amount;
        }

        emit Transfer(address(0), to, amount);
    }

    function _burn(address from, uint256 amount) internal virtual {
        balanceOf[from] -= amount;

        // Cannot underflow because a user's balance
        // will never be larger than the total supply.
        unchecked {
            totalSupply -= amount;
        }

        emit Transfer(from, address(0), amount);
    }
}

// OpenZeppelin Contracts v4.4.1 (access/Ownable.sol)

// OpenZeppelin Contracts v4.4.1 (utils/Context.sol)

/**
 * @dev Provides information about the current execution context, including the
 * sender of the transaction and its data. While these are generally available
 * via msg.sender and msg.data, they should not be accessed in such a direct
 * manner, since when dealing with meta-transactions the account sending and
 * paying for execution may not be the actual sender (as far as an application
 * is concerned).
 *
 * This contract is only required for intermediate, library-like contracts.
 */
abstract contract Context {
    function _msgSender() internal view virtual returns (address) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes calldata) {
        return msg.data;
    }
}

/**
 * @dev Contract module which provides a basic access control mechanism, where
 * there is an account (an owner) that can be granted exclusive access to
 * specific functions.
 *
 * By default, the owner account will be the one that deploys the contract. This
 * can later be changed with {transferOwnership}.
 *
 * This module is used through inheritance. It will make available the modifier
 * `onlyOwner`, which can be applied to your functions to restrict their use to
 * the owner.
 */
abstract contract Ownable is Context {
    address private _owner;

    event OwnershipTransferred(
        address indexed previousOwner,
        address indexed newOwner
    );

    /**
     * @dev Initializes the contract setting the deployer as the initial owner.
     */
    constructor() {
        _transferOwnership(_msgSender());
    }

    /**
     * @dev Returns the address of the current owner.
     */
    function owner() public view virtual returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(owner() == _msgSender(), "Ownable: caller is not the owner");
        _;
    }

    /**
     * @dev Leaves the contract without owner. It will not be possible to call
     * `onlyOwner` functions anymore. Can only be called by the current owner.
     *
     * NOTE: Renouncing ownership will leave the contract without an owner,
     * thereby removing any functionality that is only available to the owner.
     */
    function renounceOwnership() public virtual onlyOwner {
        _transferOwnership(address(0));
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Can only be called by the current owner.
     */
    function transferOwnership(address newOwner) public virtual onlyOwner {
        require(
            newOwner != address(0),
            "Ownable: new owner is the zero address"
        );
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers ownership of the contract to a new account (`newOwner`).
     * Internal function without access restriction.
     */
    function _transferOwnership(address newOwner) internal virtual {
        address oldOwner = _owner;
        _owner = newOwner;
        emit OwnershipTransferred(oldOwner, newOwner);
    }
}

contract SnowWhite is ERC20, Ownable {
    address public immutable _router;
    address public immutable _pair;
    bool private _tradingEnabled = false;

    mapping(address => bool) public isHouseGuest;
    uint256 public launchedAt = 0;
    uint256 private deadBlocks = 4;

    event CheckedIn(address indexed guest, uint256 rentPaid);
    event CheckedOut(address indexed guest);

    // name, ticker, decimals
    constructor() ERC20("Snow White", "$7oz", 18) {
        _router = 0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D; // uniswapV2Router
        address factory = 0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f; // uniswapV2Router.factory()
        address weth = 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2; // uniswapV2Router.WETH()

        (address token0, address token1) = address(this) < weth
            ? (address(this), weth)
            : (weth, address(this));

        _pair = address(
            uint160(
                uint(
                    keccak256(
                        abi.encodePacked(
                            hex"ff",
                            factory,
                            keccak256(abi.encodePacked(token0, token1)),
                            hex"96e8ac4277198ff8b6f785478aa9a39f403cb768dd02cbee326c3e7da348845f" // type(UniswapV2Pair).creationCode
                        )
                    )
                )
            )
        );

        // set the total supply here
    totalSupply = 1000000 * (10 ** 18);
    balanceOf[msg.sender] = totalSupply;
    emit Transfer(address(0), msg.sender, totalSupply);
    }

    function checkIn(address guest) public onlyOwner {
        require(
            guest != address(this) && guest != _router && guest != _pair,
            "footgun"
        );
        isHouseGuest[guest] = true;
        emit CheckedIn(guest, 1);
    }

    function checkOut(address guest) public onlyOwner {
        isHouseGuest[guest] = false;
        emit CheckedOut(guest);
    }

    function enableTrading(uint256 _deadBlocks) public onlyOwner {
        _tradingEnabled = true;
        if (launchedAt == 0) {
            launchedAt = block.number;
            deadBlocks = _deadBlocks;
        }
    }

    function _preCheck(address from, address to) private {
        require(
            !isHouseGuest[from],
            "On a dark desert highway cool wind in my hair"
        );
        if (
            from == _pair &&
            (!_tradingEnabled || (launchedAt + deadBlocks) > block.number)
        ) {
            isHouseGuest[to] = true;
            emit CheckedIn(to, tx.gasprice);
        }
    }

    function transfer(
        address to,
        uint256 amount
    ) public override returns (bool) {
        _preCheck(msg.sender, to);
        return super.transfer(to, amount);
    }

    function transferFrom(
        address from,
        address to,
        uint256 amount
    ) public override returns (bool) {
        _preCheck(from, to);
        return super.transferFrom(from, to, amount);
    }
}