"""Deterministic builder for the single Pi-facing Thoth session skill."""

import argparse
import sys
from pathlib import Path

HARNESS_ROOT = Path(__file__).resolve().parents[1]
SKILL_ROOT = HARNESS_ROOT / ".pi" / "skills" / "tht-sessione"
MODULE_ROOT = SKILL_ROOT / "modules"
TEMPLATE_PATH = SKILL_ROOT / "projection.md.tmpl"
PROJECTION_PATH = SKILL_ROOT / "SKILL.md"

# This tuple is the composition contract. Never derive it from directory order.
FRAGMENT_ORDER = (
    ("{{EVIDENCE_RUNTIME_SEARCH}}", "evidence/runtime-search.md"),
    ("{{DISAMBIGUATION_OPEN_AMBIGUITY}}", "disambiguation/open-ambiguity.md"),
    ("{{DISAMBIGUATION_INSTRUCTIONS}}", "disambiguation/phase-1.md"),
    ("{{MEMORY_INSTRUCTIONS}}", "memory/phase-2.md"),
    ("{{DISAMBIGUATION_REWRITING_INSTRUCTIONS}}", "disambiguation/phase-3.md"),
    ("{{MEMORY_SOLVED_SEARCH_F4}}", "memory/solved-search-f4.md"),
    ("{{DISAMBIGUATION_SCHEMA_GROUNDING}}", "disambiguation/schema-grounding.md"),
    ("{{EVIDENCE_FORMULA_PROPOSALS}}", "evidence/formula-proposals.md"),
    ("{{MEMORY_SOLVED_SEARCH_F6}}", "memory/solved-search-f6.md"),
    ("{{MEMORY_SOLVED_SEARCH_F7}}", "memory/solved-search-f7.md"),
    ("{{MEMORY_PROMOTION_F8}}", "memory/phase-8-promotion.md"),
    ("{{MEMORY_SOLVED_FINALIZATION}}", "memory/solved-finalization.md"),
)


def render_projection(*, template: bytes | None = None) -> bytes:
    projection = TEMPLATE_PATH.read_bytes() if template is None else template
    for marker_text, filename in FRAGMENT_ORDER:
        marker = marker_text.encode()
        if projection.count(marker) != 1:
            raise ValueError(f"projection placeholder {marker_text} must occur exactly once")
        fragment = (MODULE_ROOT / filename).read_bytes().rstrip(b"\n")
        projection = projection.replace(marker, fragment)
    return projection


def projection_is_current(path: Path = PROJECTION_PATH) -> bool:
    return path.exists() and path.read_bytes() == render_projection()


def write_projection(path: Path = PROJECTION_PATH) -> None:
    path.write_bytes(render_projection())


def main(argv: list[str] | None = None) -> int:
    parser = argparse.ArgumentParser(description=__doc__)
    action = parser.add_mutually_exclusive_group(required=True)
    action.add_argument("--check", action="store_true", help="fail if SKILL.md is stale")
    action.add_argument("--write", action="store_true", help="regenerate SKILL.md")
    args = parser.parse_args(argv)

    if args.write:
        write_projection()
        print(f"generated {PROJECTION_PATH}")
        return 0
    if projection_is_current():
        print(f"up to date: {PROJECTION_PATH}")
        return 0
    print(
        f"stale projection: run `python -m tht.pi_skill_projection --write` from {HARNESS_ROOT}",
        file=sys.stderr,
    )
    return 1


if __name__ == "__main__":
    raise SystemExit(main())