"""C2 task → Simulation output mapping.

apply_task_to_simulation() implements the full §0.11 contract:
  1. execution_result — append "$ <command>\n<output>\n" block.
  2. executed_at — set from task.completed_at when currently null.
  3. commands — append task.command deduplicated line-by-line.

Caller is responsible for committing the session.
"""
from __future__ import annotations

from datetime import UTC, datetime

from backend.app.models.c2_task import C2Task
from backend.app.models.simulation import Simulation


def apply_task_to_simulation(task: C2Task, simulation: Simulation) -> None:
    """Apply completed task data to simulation fields per §0.11.

    Idempotent: no-op when task.mapping_applied is already True.
    Always sets mapping_applied = True on exit so the task is never re-processed.
    """
    if task.mapping_applied:
        return

    output = (task.output or "").strip()

    # 1) execution_result — "$ <command>\n<output>\n" block, only when output is non-empty.
    if output:
        block = f"$ {task.command}\n{output}\n"
        existing = simulation.execution_result or ""
        if existing:
            sep = "" if existing.endswith("\n") else "\n"
            simulation.execution_result = existing + sep + block
        else:
            simulation.execution_result = block

    # 2) executed_at — set once from the first completed task's timestamp.
    if simulation.executed_at is None and task.completed_at is not None:
        simulation.executed_at = task.completed_at

    # 3) commands — append deduplicated line.
    if task.command:
        existing_cmds = (simulation.commands or "").splitlines()
        if task.command.strip() not in (line.strip() for line in existing_cmds):
            if simulation.commands:
                simulation.commands = simulation.commands + "\n" + task.command
            else:
                simulation.commands = task.command

    simulation.updated_at = datetime.now(UTC)
    task.mapping_applied = True