"""Variant instantiation prompt (D-029, REQ-3-005).

The model's ONLY job is to render already-sampled slot values into a task
statement — it never invents parameters (the seeded sampler is pure code)
and never changes difficulty. Prompt-injection surface is bounded: the
variable inputs are the skeleton text, the seeded slot values, and the
template title — nothing from the learner's environment.
"""

from __future__ import annotations

from typing import TYPE_CHECKING

from ..llm.types import Message

if TYPE_CHECKING:  # pragma: no cover - keeps this module pure text
    from ..variants.templates import TaskTemplate

VARIANT_SYSTEM_PROMPT = (
    "You instantiate per-learner task variants for a competency-based AI school. "
    "You receive a task statement skeleton and ALREADY-SAMPLED slot values. "
    "Render the slot values into the skeleton, producing a complete, unambiguous "
    "task statement a learner can build against. Rules:\n"
    "- Use EXACTLY the given slot values; do not invent, rename, or add parameters.\n"
    "- Keep the engineering depth IDENTICAL across draws: slot values change the "
    "scenario, never the difficulty or scope.\n"
    "- Keep the statement in the same language and register as the skeleton.\n"
    "- Output STRICT JSON only: {\"statement\": \"<rendered statement>\"}.\n"
)

VARIANT_SCHEMA_HINT = '{"statement": "<complete rendered task statement string>"}'


def render_variant_prompt(template: TaskTemplate, params: dict[str, str | int]) -> list[Message]:
    """Messages for one seeded instantiation (D-020 defense drives the call)."""
    slot_lines = "\n".join(f"  {{{slot.name}}} = {params[slot.name]!r}" for slot in template.slots)
    user = (
        f"Template: {template.title} (id={template.id})\n"
        f"Statement skeleton:\n{template.statement_skeleton}\n\n"
        f"Seeded slot values (use EXACTLY these):\n{slot_lines}\n\n"
        "Render the complete task statement now."
    )
    return [
        Message(role="system", content=VARIANT_SYSTEM_PROMPT),
        Message(role="user", content=user),
    ]