#!/usr/bin/python3

from os.path import exists, join as path_join
from os import system, environ, makedirs
from argparse import ArgumentParser
from sys import stdin
import subprocess

# Paths
PATHS = {
	"src_dir": "src/",
	"build_dir": "build/",
	"template": "template.c",
	"substitute": "substituted.c",
	"output": "render_bytebeat"
}

# Solve paths
PATHS["template"] = path_join(PATHS["src_dir"], PATHS["template"])
PATHS["substitute"] = path_join(PATHS["build_dir"], PATHS["substitute"])
PATHS["output"] = path_join(PATHS["build_dir"], PATHS["output"])

# Default parameters
DEFAULT_PARAMETERS = {
	"CC": "gcc",
	"CC_FLAGS": "-Ofast -Wall -Wextra -Wpedantic",
	"INPUT_FILE": PATHS["substitute"],
	"OUTPUT_FILE": PATHS["output"]
}

def fetch(name: str):
	return res if (res := environ.get(name)) else DEFAULT_PARAMETERS[name]

def read_file(path: str) -> str:
	return open(path, "r", encoding="utf-8-sig").read()

def rewrite_file(path: str, content: str):
	return open(path, "w", encoding="utf-8-sig").write(content)

def read_from_file_or_stdin(path: str) -> str:
	if path == "-":
		return "\n".join(stdin)
	elif exists(path):
		return read_file(path)
	else:
		print("The specified file doesn't exist")
		raise SystemExit

def substitute_var(placeholder: str, replacement, text: str) -> str:
	return text.replace(f"`{placeholder}`", str(replacement))

CC = fetch("CC")
CC_FLAGS = fetch("CC_FLAGS")
INPUT_FILE = fetch("INPUT_FILE")
OUTPUT_FILE = fetch("OUTPUT_FILE")

if __name__ == "__main__":
	parser = ArgumentParser(description=\
		"Substitutes supplied C (non-JavaScript!) bytebeat into the template, "
		"then attempts to compile the instance of the template. Uses "
		"environmental variables `CC`, `CC_FLAGS`, `INPUT_FILE`, "
		"`OUTPUT_FILE`.")
	parser.add_argument("file", type=str,
		help="bytebeat formula file")
	parser.add_argument("-r", "--sample-rate", default=8000, type=int,
		help="sample rate (Hz)")
	parser.add_argument("-p", "--final-sample-rate", default=None, type=int,
		help="convert the output to a different sample rate (usually one that "
		"is set in the system, to improve sound quality) during generation "
		"(not just reinterpretation)")
	parser.add_argument("-b", "--bit-depth", default=8, type=int,
		help="bit depth")
	parser.add_argument("-s", "--signed", default=False, action="store_true",
		help="is signed?")
	parser.add_argument("-c", "--channels", default=1, type=int,
		help="amount of channels")
	parser.add_argument("-t", "--seconds", default=30, type=int,
		help="length (seconds)")
	parser.add_argument("-a", "--no-return", default=False, action="store_true",
		help="do not insert return statement before the code")
	args = parser.parse_args()

	bytebeat_contents = read_from_file_or_stdin(args.file).strip()

	if not bytebeat_contents:
		print("No valid contents")
		raise SystemExit

	# - Compilation
	makedirs(PATHS["build_dir"], exist_ok=True)

	if not args.no_return:  # Insert return statement
		bytebeat_contents = f"\treturn\n\n{bytebeat_contents}"

	final_sample_rate_code = ""
	if not args.final_sample_rate is None:
		sample_rate_ratio = args.sample_rate / args.final_sample_rate
		final_sample_rate_code = f"w *= {sample_rate_ratio}L;"
		args.sample_rate = args.final_sample_rate

	substitute = read_file(PATHS["template"])
	substitute = substitute_var("bytebeat_contents",
		bytebeat_contents, substitute)
	substitute = substitute_var("sample_rate",
		args.sample_rate, substitute)
	substitute = substitute_var("final_sample_rate_code",
		final_sample_rate_code, substitute)
	substitute = substitute_var("bit_depth",
		args.bit_depth, substitute)
	substitute = substitute_var("is_signed",
		"1" if args.signed else "0", substitute)
	substitute = substitute_var("channels",
		args.channels, substitute)
	substitute = substitute_var("seconds",
		args.seconds, substitute)
	rewrite_file(PATHS["substitute"], substitute)

	# Compile by invoking the shell script
	print("Compiling")

	# Let the system execute aliases by calling os.system
	system(" ".join([CC, CC_FLAGS, INPUT_FILE, "-o", OUTPUT_FILE]))