from __future__ import annotations

import json
import os
from pathlib import Path

from configs import cfg
from src.kd_contracts import (
    PROVENANCE_SCHEMA_VERSION,
    build_shard_schema,
    canonical_revision,
    collect_model_vocab_sizes,
    sha256_file,
)

def resolve_model_vocab_size(model, tokenizer, label: str, log) -> int:
    model_sizes = collect_model_vocab_sizes(model)
    if not model_sizes:
        log.error(f"{label} model does not expose a usable vocab size view.")
        raise SystemExit(1)

    unique_sizes = sorted(set(model_sizes.values()))
    if len(unique_sizes) != 1:
        details = ", ".join(f"{name}={size:,}" for name, size in sorted(model_sizes.items()))
        log.error(f"{label} vocab mismatch across checkpoint artifacts: {details}")
        raise SystemExit(1)

    model_vocab_size = unique_sizes[0]
    tokenizer_vocab_size = len(tokenizer)
    if model_vocab_size < tokenizer_vocab_size:
        log.error(
            f"{label} tokenizer length ({tokenizer_vocab_size:,}) exceeds "
            f"the model vocab size ({model_vocab_size:,})."
        )
        log.error("Repair or regenerate the checkpoint before using it for distillation.")
        raise SystemExit(1)
    if model_vocab_size > tokenizer_vocab_size:
        log.info(
            f"  {label} model vocab is padded beyond the tokenizer range: "
            f"tokenizer={tokenizer_vocab_size:,}, model={model_vocab_size:,}"
        )
    return model_vocab_size

def validate_provenance(
    prov_path: str,
    data_path: str,
    dataset,
    teacher_tokenizer_contract: dict,
    student_tokenizer_contract: dict,
    log,
) -> None:
    if not os.path.exists(prov_path):
        log.error("Missing _provenance.json in the logits directory.")
        log.error("Regenerate the current teacher-logit shard metadata.")
        raise SystemExit(1)

    with open(prov_path, "r", encoding="utf-8") as f:
        prov = json.load(f)

    schema_version = prov.get("schema_version")
    if schema_version != PROVENANCE_SCHEMA_VERSION:
        log.error(
            f"Unsupported shard provenance schema: {schema_version!r}. "
            f"Expected {PROVENANCE_SCHEMA_VERSION}."
        )
        log.error("Regenerate the teacher-logit shards.")
        raise SystemExit(1)

    teacher_meta = prov.get("teacher", {})
    student_meta = prov.get("student", {})
    current_data_sha = sha256_file(data_path)
    actual_shard_count = sum(1 for _ in Path(prov_path).parent.glob("shard_*.pt"))
    provenance_num_samples = prov.get("num_samples")
    try:
        provenance_num_samples_int = int(provenance_num_samples)
    except (TypeError, ValueError):
        log.error(f"PROVENANCE MISMATCH: num_samples is {provenance_num_samples!r}, expected an integer.")
        log.error("Regenerate compatible teacher-logit shards.")
        raise SystemExit(1)
    if provenance_num_samples_int < len(dataset):
        log.error(
            f"PROVENANCE MISMATCH: num_samples is {provenance_num_samples_int}, "
            f"but the requested dataset has {len(dataset)} samples."
        )
        log.error("Regenerate compatible teacher-logit shards.")
        raise SystemExit(1)
    if provenance_num_samples_int > len(dataset):
        log.warning(
            f"  Provenance contains {provenance_num_samples_int:,} samples; "
            f"training is using the first {len(dataset):,}. This is expected for smoke tests."
        )

    expected_pairs = [
        ("shard_count", prov.get("shard_count"), actual_shard_count),
        ("samples_per_shard", prov.get("samples_per_shard"), dataset.samples_per_shard),
        ("data_sha256", prov.get("data_sha256"), current_data_sha),
        ("max_seq_len", prov.get("max_seq_len"), cfg.data.max_seq_len),
        ("top_k", prov.get("top_k"), cfg.training.top_k),
        ("temperature", prov.get("temperature"), float(cfg.training.temperature)),
        ("teacher.model", teacher_meta.get("model"), cfg.model.teacher),
        (
            "teacher.revision",
            teacher_meta.get("revision"),
            canonical_revision(cfg.model.teacher_revision),
        ),
        (
            "teacher.tokenizer_size",
            teacher_meta.get("tokenizer_size"),
            teacher_tokenizer_contract["full_vocab_size"],
        ),
        (
            "teacher.tokenizer_fingerprint",
            teacher_meta.get("tokenizer_fingerprint"),
            teacher_tokenizer_contract["fingerprint"],
        ),
        ("student.model", student_meta.get("model"), getattr(cfg.model, "tokenizer", cfg.model.student)),
        (
            "student.revision",
            student_meta.get("revision"),
            canonical_revision(getattr(cfg.model, "tokenizer_revision", cfg.model.student_revision)),
        ),
        (
            "student.tokenizer_size",
            student_meta.get("tokenizer_size"),
            student_tokenizer_contract["full_vocab_size"],
        ),
        (
            "student.tokenizer_fingerprint",
            student_meta.get("tokenizer_fingerprint"),
            student_tokenizer_contract["fingerprint"],
        ),
    ]

    warn_only_fields = {
        "teacher.tokenizer_fingerprint",
        "student.tokenizer_fingerprint",
    }

    for field_name, found, expected in expected_pairs:
        if found != expected:
            if field_name in warn_only_fields:
                log.warning(
                    f"  Provenance WARNING (non-fatal): {field_name} is {found!r}, "
                    f"expected {expected!r}. This is likely due to a transformers "
                    f"library version change. Continuing because vocab sizes match."
                )
            else:
                log.error(
                    f"PROVENANCE MISMATCH: {field_name} is {found!r}, expected {expected!r}."
                )
                log.error("Regenerate compatible teacher-logit shards.")
                raise SystemExit(1)

    provenance_data_path = prov.get("data_path")
    current_data_path = str(Path(data_path).resolve())
    if provenance_data_path != current_data_path:
        log.warning(
            "  Provenance data_path differs because logits were likely generated on another machine: "
            f"{provenance_data_path!r} vs {current_data_path!r}. "
            "Continuing because data_sha256 matches."
        )

    shard_schema = prov.get("shard_schema")
    expected_shard_schema = build_shard_schema()
    if shard_schema != expected_shard_schema:
        log.error(
            f"PROVENANCE MISMATCH: shard_schema is {shard_schema!r}, "
            f"expected {expected_shard_schema!r}."
        )
        log.error("Regenerate compatible teacher-logit shards.")
        raise SystemExit(1)

    log.info("  Provenance:  PASS (teacher shards match the current config and dataset)")