"""Readers + writers: TSV (sandbox corpus + round-trip), JSON, CoNLL-U, JSONL.

Also: tokenization helpers and the alignment validator that enforces the
"don't add / remove / split / merge / reorder tokens" rule from the system
prompt.
"""
from __future__ import annotations

import csv
import io
import json
import unicodedata
from pathlib import Path
from typing import Iterable

from schemas import AnnotationSchema


# ---------------------------------------------------------------------------
# Tokenization
# ---------------------------------------------------------------------------

def tokenize(text: str, strategy: str = "whitespace") -> list[str]:
    if strategy == "whitespace":
        return text.split()
    if strategy == "newline":
        return [line for line in text.splitlines() if line.strip()]
    if strategy == "as_is":
        # treat the text as already-tokenized, one token per line (preferred)
        if "\n" in text.strip():
            return [line for line in text.splitlines() if line.strip()]
        return text.split()
    raise ValueError(f"Unknown tokenize strategy: {strategy}")


def validate_alignment(input_tokens: list[str], output_tokens: list[str]) -> list[str]:
    """Strict alignment check (kept for callers that want hard equality)."""
    errors = []
    if len(input_tokens) != len(output_tokens):
        errors.append(
            f"Token count mismatch: input has {len(input_tokens)}, output has {len(output_tokens)}."
        )
        return errors
    for i, (a, b) in enumerate(zip(input_tokens, output_tokens)):
        if a != b:
            errors.append(f"Token {i}: input={a!r} but output surface={b!r}")
    return errors


_PUNCT_TRAILING = ",.;:·•—–-«»\"'!?)]"


def align_or_warn(input_tokens: list[str], output_tokens: list[str]) -> tuple[str, list[str]]:
    """Lenient alignment. Returns (status, messages).

    status ∈ { 'ok', 'length_mismatch', 'drift' }.
    - 'ok'              → identical surfaces (after NFC normalization).
    - 'length_mismatch' → token count differs (caller should reject).
    - 'drift'           → same length but surfaces differ (case / unicode form /
                          punctuation). Caller should accept positionally and
                          force input surfaces; messages list the offenders.
    """
    if len(input_tokens) != len(output_tokens):
        return 'length_mismatch', [
            f"Token count mismatch: input has {len(input_tokens)}, output has {len(output_tokens)}."
        ]
    messages: list[str] = []
    for i, (a, b) in enumerate(zip(input_tokens, output_tokens)):
        if a == b:
            continue
        a_n = unicodedata.normalize('NFC', a)
        b_n = unicodedata.normalize('NFC', b)
        if a_n == b_n:
            continue  # silent: pure unicode-form drift
        if a_n.lower() == b_n.lower():
            messages.append(f"token {i}: case differs ({a!r} vs {b!r})")
            continue
        if a_n.rstrip(_PUNCT_TRAILING) == b_n.rstrip(_PUNCT_TRAILING):
            messages.append(f"token {i}: trailing-punct differs ({a!r} vs {b!r})")
            continue
        messages.append(f"token {i}: surface differs ({a!r} vs {b!r})")
    return ('drift' if messages else 'ok'), messages


# ---------------------------------------------------------------------------
# Sandbox TSV reader (matches EACL2026-historical-languages format)
# ---------------------------------------------------------------------------

def read_sandbox_tsv(path: Path, max_rows: int = -1) -> list[dict]:
    """Read text_form/form/lemma/pos TSV. Returns list of row dicts."""
    rows: list[dict] = []
    with open(path, encoding="utf-8") as f:
        reader = csv.DictReader(f, delimiter="\t")
        for i, r in enumerate(reader):
            rows.append(r)
            if max_rows > 0 and len(rows) >= max_rows:
                break
    return rows


def sandbox_sentence(rows: list[dict], start: int, n_tokens: int) -> tuple[list[str], list[dict]]:
    """Slice a window of `n_tokens` from sandbox rows.

    Returns (surface_tokens, gold_token_dicts) where each gold dict has
    {"surface": text_form, "lemma": lemma, "pos": pos}.
    """
    window = rows[start : start + n_tokens]
    surfaces = [r["text_form"] for r in window]
    gold = [{"surface": r["text_form"], "lemma": r["lemma"], "pos": r["pos"]} for r in window]
    return surfaces, gold


# ---------------------------------------------------------------------------
# Exports
# ---------------------------------------------------------------------------

def export_tsv(annotation: dict, schema: AnnotationSchema) -> str:
    """Round-trip-friendly TSV.

    Columns: text_form, form, lemma, pos when those fields exist; otherwise
    text_form + each top-level schema field in order.
    """
    tokens = annotation.get("tokens", [])
    field_names = [f.name for f in schema.fields]
    has_lemma = "lemma" in field_names
    pos_key = next((k for k in ("pos", "upos") if k in field_names), None)
    if has_lemma and pos_key:
        header = ["text_form", "form", "lemma", "pos"]
        rows = [header]
        for t in tokens:
            surf = t.get("surface", "")
            rows.append([surf, surf.lower(), str(t.get("lemma", "") or ""), str(t.get(pos_key, "") or "")])
        return "\n".join("\t".join(r) for r in rows) + "\n"
    # generic
    header = ["text_form"] + field_names
    rows = [header]
    for t in tokens:
        row = [t.get("surface", "")]
        for fname in field_names:
            v = t.get(fname, "")
            if isinstance(v, dict):
                v = json.dumps(v, ensure_ascii=False)
            row.append(str(v) if v is not None else "")
        rows.append(row)
    return "\n".join("\t".join(r) for r in rows) + "\n"


def export_json(annotation: dict) -> str:
    return json.dumps(annotation, ensure_ascii=False, indent=2)


def export_conllu(annotation: dict, schema: AnnotationSchema) -> str:
    """Emit CoNLL-U: ID FORM LEMMA UPOS XPOS FEATS HEAD DEPREL DEPS MISC.

    Unknown fields use `_`. Multi-sentence input not supported (one sentence
    per annotation); the caller can concatenate.
    """
    field_names = [f.name for f in schema.fields]
    lemma_key = "lemma" if "lemma" in field_names else None
    upos_key = next((k for k in ("upos", "pos") if k in field_names), None)
    feats_key = "features" if "features" in field_names else None

    lines = []
    sid = annotation.get("sentence_id", "s1")
    lang = annotation.get("language", "")
    lines.append(f"# sent_id = {sid}")
    if lang:
        lines.append(f"# language = {lang}")
    surfaces = [t.get("surface", "") for t in annotation.get("tokens", [])]
    lines.append(f"# text = {' '.join(surfaces)}")
    for i, t in enumerate(annotation.get("tokens", []), 1):
        form = t.get("surface", "_") or "_"
        lemma = (t.get(lemma_key) or "_") if lemma_key else "_"
        upos = (t.get(upos_key) or "_") if upos_key else "_"
        if feats_key and isinstance(t.get(feats_key), dict):
            kv = [f"{k}={v}" for k, v in t[feats_key].items() if v]
            feats = "|".join(kv) if kv else "_"
        else:
            feats = "_"
        lines.append("\t".join([str(i), form, str(lemma), str(upos), "_", feats, "_", "_", "_", "_"]))
    return "\n".join(lines) + "\n\n"


def export_jsonl_finetune(
    annotation: dict,
    system_prompt: str,
    user_prompt: str,
) -> str:
    """One-line JSON shaped for chat-style fine-tuning APIs."""
    record = {
        "messages": [
            {"role": "system", "content": system_prompt},
            {"role": "user", "content": user_prompt},
            {"role": "assistant", "content": json.dumps(annotation, ensure_ascii=False)},
        ]
    }
    return json.dumps(record, ensure_ascii=False) + "\n"


def write_temp(content: str, suffix: str) -> str:
    """Write to a temp file and return path (used by gr.File downloads)."""
    import tempfile
    fd, name = tempfile.mkstemp(suffix=suffix, prefix="lrec_annot_")
    with open(fd, "w", encoding="utf-8") as f:
        f.write(content)
    return name