"""Read-only evaluation helpers for application job execution statistics."""

from typing import TYPE_CHECKING

from ..components.job import BackgroundJob, BaseJob, CronJob, StreamJob
from .counter import global_counter_get, global_counter_get_all

if TYPE_CHECKING:
    from ..components.application_context import ApplicationContext


_JOB_ENTRY_CLASSES = {CronJob, StreamJob, BackgroundJob, BaseJob}
_TOKEN_METRICS = (
    "input_tokens",
    "output_tokens",
    "cache_read_tokens",
    "cache_write_tokens",
    "reasoning_tokens",
    "total_tokens",
)


def check_job_count(job_name: str, app_context: "ApplicationContext") -> int:
    """Return the application-lifetime execution count for a registered job.

    ``app_context`` scopes the lookup because ReMe does not maintain a global
    current Application instance. Unknown job names use the same ``KeyError``
    contract as :meth:`Application.run_job`.
    """
    job = app_context.jobs.get(job_name)
    if job is None:
        raise KeyError(f"Job '{job_name}' not found")

    entry_class = next((cls for cls in type(job).mro() if cls in _JOB_ENTRY_CLASSES), None)
    if entry_class is None:
        raise TypeError(f"Job '{job_name}' does not inherit from a supported job implementation")
    # pylint: disable-next=protected-access
    return global_counter_get(app_context.metadata, job._counter_key(entry_class))


class JobCountTracker:
    """Measure registered job calls made while this context is active."""

    def __init__(self, job_names: list[str], app_context: "ApplicationContext") -> None:
        self.job_names = list(dict.fromkeys(job_names))
        self.app_context = app_context
        self._start_counts: dict[str, int] = {}
        self.counts: dict[str, int] = {}

    def __enter__(self) -> dict[str, int]:
        self._start_counts = {name: check_job_count(name, self.app_context) for name in self.job_names}
        return self.counts

    def __exit__(self, exc_type, exc_value, traceback) -> bool:
        self.counts.update(
            {
                name: check_job_count(name, self.app_context) - start_count
                for name, start_count in self._start_counts.items()
            },
        )
        return False


def track_job_counts(job_names: list[str], app_context: "ApplicationContext") -> JobCountTracker:
    """Return a context manager that reports call deltas for ``job_names``.

    Example:

    .. code-block:: python

        with track_job_counts(["search"], app.context) as counts:
            await app.run_job("agentic_answer", query="...")
        assert counts == {"search": 2}
    """
    return JobCountTracker(job_names, app_context)


def check_agent_token_count(
    agent_name: str,
    app_context: "ApplicationContext",
    metric: str = "total_tokens",
) -> int:
    """Return one application-lifetime token metric for an agent wrapper.

    The agent name is the configured ``agent_wrapper`` component name (for
    example ``"bench"``), and ``metric`` is one leaf in ReMe's token counter
    tree, such as ``input_tokens`` or ``total_tokens``.
    """
    return global_counter_get(app_context.metadata, ["__token_counter", agent_name, metric])


def check_agent_token_usage(agent_name: str, app_context: "ApplicationContext") -> dict[str, int | None]:
    """Return all token metrics currently accumulated for one agent wrapper.

    Optional cache and reasoning metrics remain ``None`` until the backend has
    reported them at least once. This keeps unknown usage distinct from zero.
    """
    tree = global_counter_get_all(app_context.metadata, ["__token_counter", agent_name])
    children = tree.get("children", {}) if tree is not None else {}
    usage: dict[str, int | None] = {}
    for metric in _TOKEN_METRICS:
        node = children.get(metric)
        usage[metric] = node["value"] if node is not None else None
    return usage


class AgentTokenCountTracker:
    """Measure one token metric for agent wrappers during a context block."""

    def __init__(
        self,
        agent_names: list[str],
        app_context: "ApplicationContext",
        metric: str = "total_tokens",
    ) -> None:
        self.agent_names = list(dict.fromkeys(agent_names))
        self.app_context = app_context
        self.metric = metric
        self._start_counts: dict[str, int] = {}
        self.counts: dict[str, int] = {}

    def __enter__(self) -> dict[str, int]:
        self._start_counts = {
            name: check_agent_token_count(name, self.app_context, self.metric)
            for name in self.agent_names
        }
        return self.counts

    def __exit__(self, exc_type, exc_value, traceback) -> bool:
        self.counts.update(
            {
                name: check_agent_token_count(name, self.app_context, self.metric) - start_count
                for name, start_count in self._start_counts.items()
            },
        )
        return False


def track_agent_token_counts(
    agent_names: list[str],
    app_context: "ApplicationContext",
    metric: str = "total_tokens",
) -> AgentTokenCountTracker:
    """Return a context manager that reports agent token deltas.

    Example:

    .. code-block:: python

        with track_agent_token_counts(["bench"], app.context) as counts:
            await app.run_job("agentic_answer", query="...")
        assert counts["bench"] > 0
    """
    return AgentTokenCountTracker(agent_names, app_context, metric)


class AgentTokenUsageTracker:
    """Measure all token metrics for agent wrappers during a context block."""

    def __init__(self, agent_names: list[str], app_context: "ApplicationContext") -> None:
        self.agent_names = list(dict.fromkeys(agent_names))
        self.app_context = app_context
        self._start_usage: dict[str, dict[str, int | None]] = {}
        self._start_report_counts: dict[str, dict[str, int]] = {}
        self.usages: dict[str, dict[str, int | None]] = {}

    def __enter__(self) -> dict[str, dict[str, int | None]]:
        self._start_usage = {
            name: check_agent_token_usage(name, self.app_context) for name in self.agent_names
        }
        self._start_report_counts = {
            name: {
                metric: check_agent_token_count(name, self.app_context, f"{metric}_reported_calls")
                for metric in ("cache_read_tokens", "cache_write_tokens", "reasoning_tokens")
            }
            for name in self.agent_names
        }
        return self.usages

    def __exit__(self, exc_type, exc_value, traceback) -> bool:
        for name in self.agent_names:
            end_usage = check_agent_token_usage(name, self.app_context)
            delta: dict[str, int | None] = {}
            for metric in _TOKEN_METRICS:
                current = end_usage[metric]
                start = self._start_usage[name][metric]
                if metric in self._start_report_counts[name]:
                    end_reports = check_agent_token_count(name, self.app_context, f"{metric}_reported_calls")
                    if end_reports == self._start_report_counts[name][metric]:
                        delta[metric] = None
                        continue
                delta[metric] = (current or 0) - (start or 0)
            self.usages[name] = delta
        return False


def track_agent_token_usage(
    agent_names: list[str],
    app_context: "ApplicationContext",
) -> AgentTokenUsageTracker:
    """Return a context manager that reports full per-agent token usage deltas."""
    return AgentTokenUsageTracker(agent_names, app_context)