import contextlib
import os
from datetime import datetime

import aiofiles
import orjson
from environs import Env

env = Env()
env.read_env()

unit_log_file: str = env.str("UNIT_LOG_FILE")


def escape_label_value(value):
    return value.replace("\\", "\\\\").replace('"', '\\"').replace("\n", "\\n")


async def read_and_process_logs():
    metric_lines = []

    if os.path.exists(unit_log_file):
        async with aiofiles.open(unit_log_file, mode="r+") as f:
            lines = await f.readlines()
            await f.truncate(0)

        for line in lines:
            with contextlib.suppress(Exception):
                log_data = orjson.loads(line)
                request_time = float(log_data["request_time"])
                url = log_data["url"]
                http_method = log_data["http_method"]
                datetime_str = log_data["datetime"]

                # Parse datetime_str to Unix timestamp in milliseconds
                dt = datetime.strptime(datetime_str, "%d/%b/%Y:%H:%M:%S %z")
                timestamp_ms = int(dt.timestamp() * 1000)

                labels = (
                    f'url="{escape_label_value(url)}",'
                    f'http_method="{escape_label_value(http_method)}"'
                )

                # Generate the metric line
                metric_line = f"request_duration_seconds{{{labels}}} {request_time} {timestamp_ms}"
                metric_lines.append(metric_line)
    return metric_lines


async def generate_metrics_text():
    lines = [
        "# HELP request_duration_seconds Request duration in seconds",
        "# TYPE request_duration_seconds gauge",
    ]

    metric_lines = await read_and_process_logs()

    lines.extend(metric_lines)

    return "\n".join(lines) + "\n"


async def app(scope, receive, send):
    if scope["type"] == "http":
        if scope["path"] == "/metrics":
            headers = [(b"content-type", b"text/plain; charset=utf-8")]
            metrics_text = await generate_metrics_text()
            body = metrics_text.encode("utf-8")

            await send({"type": "http.response.start", "status": 200, "headers": headers})
            await send({"type": "http.response.body", "body": body})
        else:
            await send(
                {
                    "type": "http.response.start",
                    "status": 404,
                    "headers": [(b"content-type", b"text/plain; charset=utf-8")],
                }
            )
            await send({"type": "http.response.body", "body": b"Not Found"})