"""Reading what a driver reported."""

import json


class DriverReport:
    """The JSON one driver run wrote to stdout."""

    def __init__(self, result):
        self.result = result

    @staticmethod
    def tail(text, lines=20):
        return "\n".join(text.splitlines()[-lines:])

    @staticmethod
    def last_json_object(text):
        """The driver's report, however it ended up on the line.

        Not "the last line starting with {": worlds write to raw stdout
        during generation, and one that writes without a trailing
        newline leaves its output glued to the front of the report -
        Super Metroid's randomizer emits a bare "*" per retry, so the
        report arrives as "*{...}" and would read as no report at all.
        """
        for line in reversed(text.splitlines()):
            line = line.strip()
            start = line.find("{")
            while start != -1:
                try:
                    return json.loads(line[start:])
                except json.JSONDecodeError:
                    start = line.find("{", start + 1)
        return None

    @property
    def data(self):
        return self.last_json_object(self.result.stdout)

    def parsed(self):
        """The report, or a failure built from what it printed."""
        report = self.data
        if report is not None:
            report.setdefault("stderr_tail", self.tail(self.result.stderr))
            return report
        return {
            "game": None,
            "outcome": "failed",
            "detail": ("no JSON report on stdout "
                       f"(exit code {self.result.returncode})"),
            "elapsed_seconds": None,
            "stdout_tail": self.tail(self.result.stdout),
            "stderr_tail": self.tail(self.result.stderr),
        }