use anyhow::{bail, Context, Result};
use clap::Parser;
use rand::rngs::StdRng;
use rand::seq::SliceRandom;
use rand::SeedableRng;
use rayon::prelude::*;
use regex::Regex;
use serde::{Deserialize, Serialize};
use serde_json::{json, Value};
use std::collections::HashMap;
use std::fs::{self, File};
use std::io::{BufRead, BufReader, BufWriter, Write};
use std::path::{Path, PathBuf};
use std::sync::OnceLock;
use std::time::Instant;

const FALLBACK_LABELS: [&str; 37] = [
    "O",
    "B-TITLE_CHS",
    "I-TITLE_CHS",
    "B-TITLE_CHT",
    "I-TITLE_CHT",
    "B-TITLE_JPN",
    "I-TITLE_JPN",
    "B-TITLE_LATIN",
    "I-TITLE_LATIN",
    "B-TITLE_MIXED",
    "I-TITLE_MIXED",
    "B-PATH_TITLE_CHS",
    "I-PATH_TITLE_CHS",
    "B-PATH_TITLE_CHT",
    "I-PATH_TITLE_CHT",
    "B-PATH_TITLE_JPN",
    "I-PATH_TITLE_JPN",
    "B-PATH_TITLE_LATIN",
    "I-PATH_TITLE_LATIN",
    "B-PATH_TITLE_MIXED",
    "I-PATH_TITLE_MIXED",
    "B-PATH_SEASON",
    "I-PATH_SEASON",
    "B-SEASON",
    "I-SEASON",
    "B-EPISODE",
    "I-EPISODE",
    "B-SPECIAL",
    "I-SPECIAL",
    "B-GROUP",
    "I-GROUP",
    "B-RESOLUTION",
    "I-RESOLUTION",
    "B-SOURCE",
    "I-SOURCE",
    "B-TAG",
    "I-TAG",
];

const SOURCE_TOKEN_PATTERN: &str = r"WEB[-_ ]?DL|WEB[-_ ]?Rip|BDRip|BluRay|BDMV|BD|DVDRip|DVD|TVRip|HDTV|Netflix|NF|AMZN|Baha|CR|ABEMA|DSNP|U[-_ ]?NEXT|Hulu|AT[-_ ]?X|x26[45]|h\.?26[45]|HEVC|AVC|AV1|AAC\d*(?:\.\d+)?|AAC|FLAC|MP3|DTS|Opus|CHS|CHT|GB|BIG5|JPN?|JPSC|JPTC|繁中|简中";

static RESOLUTION_RE: OnceLock<Regex> = OnceLock::new();
static SOURCE_RE: OnceLock<Regex> = OnceLock::new();
static SOURCE_TAG_RE: OnceLock<Regex> = OnceLock::new();
static SPECIAL_TAG_RE: OnceLock<Regex> = OnceLock::new();
static SPECIAL_CODE_RE: OnceLock<Regex> = OnceLock::new();

#[derive(Parser, Debug)]
#[command(
    about = "Build split train/eval encoded AniFileBERT shard caches",
    version
)]
struct Args {
    #[arg(long)]
    input: PathBuf,

    #[arg(long)]
    vocab_file: PathBuf,

    #[arg(long)]
    output_dir: PathBuf,

    #[arg(long, default_value = "label_schema.json")]
    label_schema_file: PathBuf,

    #[arg(long, default_value_t = 128)]
    max_length: usize,

    #[arg(long, default_value_t = 25_000)]
    shard_size: usize,

    #[arg(long, default_value_t = 0)]
    limit_rows: usize,

    #[arg(long, default_value_t = 0.98)]
    train_split: f64,

    #[arg(long, default_value_t = 42)]
    seed: u64,

    #[arg(long)]
    no_shuffle: bool,

    #[arg(long, default_value_t = 0)]
    threads: usize,
}

#[derive(Debug, Deserialize)]
struct LabelSchema {
    labels: Vec<String>,
}

#[derive(Clone)]
struct SourceRow {
    row_index: usize,
    raw_line: String,
    filename: Option<String>,
    tokens: Vec<String>,
    labels: Vec<String>,
    tokenizer_variant: Option<String>,
}

#[derive(Clone)]
struct Vocab {
    ids: HashMap<String, u16>,
    pad_id: u16,
    unk_id: u16,
    cls_id: u16,
    sep_id: u16,
}

#[derive(Clone)]
struct EncodeContext {
    vocab: Vocab,
    label_ids: HashMap<String, i16>,
    max_length: usize,
}

#[derive(Serialize)]
struct ShardManifest {
    rows: usize,
    input_ids: String,
    attention_mask: String,
    labels: String,
}

#[derive(Serialize)]
struct SplitSummary {
    split: String,
    rows: usize,
    shards: usize,
    directory: String,
}

fn main() -> Result<()> {
    let args = Args::parse();
    if args.max_length < 4 {
        bail!("--max-length must be at least 4");
    }
    if args.shard_size == 0 {
        bail!("--shard-size must be positive");
    }
    if !(0.0..1.0).contains(&args.train_split) {
        bail!("--train-split must be > 0 and < 1");
    }
    if args.threads > 0 {
        rayon::ThreadPoolBuilder::new()
            .num_threads(args.threads)
            .build_global()
            .context("failed to configure rayon thread pool")?;
    }

    let started = Instant::now();
    let vocab = load_vocab(&args.vocab_file)?;
    let label_ids = load_label_ids(&args.label_schema_file)?;
    let mut rows = load_rows(&args.input, args.limit_rows)?;
    if rows.len() < 2 {
        bail!("need at least two rows to build train/eval cache");
    }

    if !args.no_shuffle {
        let mut rng = StdRng::seed_from_u64(args.seed);
        rows.shuffle(&mut rng);
    }
    let split_idx = ((rows.len() as f64) * args.train_split) as usize;
    let split_idx = split_idx.max(1).min(rows.len() - 1);
    let (train_rows, eval_rows) = rows.split_at(split_idx);

    fs::create_dir_all(&args.output_dir).with_context(|| {
        format!(
            "failed to create output directory {}",
            args.output_dir.display()
        )
    })?;

    let context = EncodeContext {
        vocab,
        label_ids,
        max_length: args.max_length,
    };
    let train_summary = write_split(
        "train",
        train_rows,
        &args.output_dir,
        &context,
        args.shard_size,
    )?;
    let eval_summary = write_split(
        "eval",
        eval_rows,
        &args.output_dir,
        &context,
        args.shard_size,
    )?;
    write_eval_records(eval_rows, &args.output_dir.join("eval_records.jsonl"))?;

    let manifest = json!({
        "format": "anifilebert.encoded_dataset_cache.v1",
        "input": args.input,
        "vocab_file": args.vocab_file,
        "label_schema_file": args.label_schema_file,
        "output_dir": args.output_dir,
        "max_length": args.max_length,
        "shard_size": args.shard_size,
        "limit_rows": args.limit_rows,
        "source_rows": train_rows.len() + eval_rows.len(),
        "train_split": args.train_split,
        "seed": args.seed,
        "shuffle": !args.no_shuffle,
        "train": train_summary,
        "eval": eval_summary,
        "eval_records": "eval_records.jsonl",
        "elapsed_seconds": started.elapsed().as_secs_f64(),
    });
    let manifest_path = args.output_dir.join("manifest.json");
    fs::write(&manifest_path, serde_json::to_string_pretty(&manifest)?)
        .with_context(|| format!("failed to write {}", manifest_path.display()))?;
    println!("{}", serde_json::to_string_pretty(&manifest)?);
    Ok(())
}

fn load_vocab(path: &Path) -> Result<Vocab> {
    let text = fs::read_to_string(path)
        .with_context(|| format!("failed to read vocab {}", path.display()))?;
    let raw: HashMap<String, u64> =
        serde_json::from_str(&text).with_context(|| format!("invalid vocab {}", path.display()))?;
    let mut ids = HashMap::with_capacity(raw.len());
    for (token, id) in raw {
        if id > u16::MAX as u64 {
            bail!("vocab id for token '{token}' exceeds u16: {id}");
        }
        ids.insert(token, id as u16);
    }
    let special = |token: &str| -> Result<u16> {
        ids.get(token)
            .copied()
            .with_context(|| format!("vocab is missing special token {token}"))
    };
    Ok(Vocab {
        pad_id: special("[PAD]")?,
        unk_id: special("[UNK]")?,
        cls_id: special("[CLS]")?,
        sep_id: special("[SEP]")?,
        ids,
    })
}

fn load_label_ids(path: &Path) -> Result<HashMap<String, i16>> {
    let labels = match fs::read_to_string(path) {
        Ok(text) => {
            serde_json::from_str::<LabelSchema>(&text)
                .with_context(|| format!("invalid label schema {}", path.display()))?
                .labels
        }
        Err(_) => FALLBACK_LABELS
            .iter()
            .map(|label| (*label).to_string())
            .collect(),
    };
    if labels.is_empty() {
        bail!("label schema has no labels");
    }
    Ok(labels
        .into_iter()
        .enumerate()
        .map(|(idx, label)| (label, idx as i16))
        .collect())
}

fn load_rows(path: &Path, limit_rows: usize) -> Result<Vec<SourceRow>> {
    let file = File::open(path).with_context(|| format!("failed to open {}", path.display()))?;
    let reader = BufReader::new(file);
    let mut rows = Vec::new();
    for (idx, line) in reader.lines().enumerate() {
        if limit_rows > 0 && rows.len() >= limit_rows {
            break;
        }
        let raw_line = line.with_context(|| format!("failed reading line {}", idx + 1))?;
        if raw_line.trim().is_empty() {
            continue;
        }
        let value: Value = serde_json::from_str(&raw_line)
            .with_context(|| format!("failed to parse JSONL line {}", idx + 1))?;
        let tokens = string_array_field(&value, "tokens", idx + 1)?;
        let labels = string_array_field(&value, "labels", idx + 1)?;
        if tokens.len() != labels.len() {
            bail!(
                "line {} has mismatched token/label lengths: {} vs {}",
                idx + 1,
                tokens.len(),
                labels.len()
            );
        }
        rows.push(SourceRow {
            row_index: idx,
            raw_line,
            filename: value
                .get("filename")
                .and_then(Value::as_str)
                .map(ToOwned::to_owned),
            tokens,
            labels,
            tokenizer_variant: value
                .get("tokenizer_variant")
                .and_then(Value::as_str)
                .map(ToOwned::to_owned),
        });
    }
    Ok(rows)
}

fn string_array_field(value: &Value, field: &str, line_no: usize) -> Result<Vec<String>> {
    let array = value
        .get(field)
        .and_then(Value::as_array)
        .with_context(|| format!("line {line_no} missing array field '{field}'"))?;
    array
        .iter()
        .map(|item| match item {
            Value::String(text) => Ok(text.clone()),
            other => Ok(match other {
                Value::Null => String::new(),
                _ => other.to_string(),
            }),
        })
        .collect()
}

fn write_split(
    split: &str,
    rows: &[SourceRow],
    output_dir: &Path,
    context: &EncodeContext,
    shard_size: usize,
) -> Result<SplitSummary> {
    let split_dir = output_dir.join(split);
    fs::create_dir_all(&split_dir)
        .with_context(|| format!("failed to create {}", split_dir.display()))?;
    let chunks = rows
        .chunks(shard_size)
        .enumerate()
        .collect::<Vec<(usize, &[SourceRow])>>();
    let shards = chunks
        .par_iter()
        .map(|(shard_idx, chunk)| write_shard(split, *shard_idx, chunk, &split_dir, context))
        .collect::<Result<Vec<_>>>()?;

    let manifest = json!({
        "format": "anifilebert.virtual_dataset.shards.v1",
        "generated_by": "tools/encoded_dataset_cache",
        "split": split,
        "max_length": context.max_length,
        "total_rows": rows.len(),
        "shards": shards,
    });
    let manifest_path = split_dir.join("manifest.json");
    fs::write(&manifest_path, serde_json::to_string_pretty(&manifest)?)
        .with_context(|| format!("failed to write {}", manifest_path.display()))?;
    Ok(SplitSummary {
        split: split.to_string(),
        rows: rows.len(),
        shards: chunks.len(),
        directory: split.to_string(),
    })
}

fn write_shard(
    split: &str,
    shard_idx: usize,
    rows: &[SourceRow],
    split_dir: &Path,
    context: &EncodeContext,
) -> Result<ShardManifest> {
    let capacity = rows.len().saturating_mul(context.max_length);
    let mut input_ids = Vec::with_capacity(capacity);
    let mut attention_mask = Vec::with_capacity(capacity);
    let mut labels = Vec::with_capacity(capacity);
    for row in rows {
        let encoded = encode_row(row, context)
            .with_context(|| format!("failed to encode source line {}", row.row_index + 1))?;
        input_ids.extend_from_slice(&encoded.0);
        attention_mask.extend_from_slice(&encoded.1);
        labels.extend_from_slice(&encoded.2);
    }

    let base = format!("part-{split}-s{shard_idx:06}");
    let input_name = format!("{base}.input_ids.npy");
    let mask_name = format!("{base}.attention_mask.npy");
    let label_name = format!("{base}.labels.npy");
    write_npy_u16(
        &split_dir.join(&input_name),
        &input_ids,
        rows.len(),
        context.max_length,
    )?;
    write_npy_u8(
        &split_dir.join(&mask_name),
        &attention_mask,
        rows.len(),
        context.max_length,
    )?;
    write_npy_i16(
        &split_dir.join(&label_name),
        &labels,
        rows.len(),
        context.max_length,
    )?;
    Ok(ShardManifest {
        rows: rows.len(),
        input_ids: input_name,
        attention_mask: mask_name,
        labels: label_name,
    })
}

fn encode_row(row: &SourceRow, context: &EncodeContext) -> Result<(Vec<u16>, Vec<u8>, Vec<i16>)> {
    let (tokens, labels) = labels_for_char_tokenizer(row);
    let mut input_ids = vec![context.vocab.pad_id; context.max_length];
    let mut attention_mask = vec![0u8; context.max_length];
    let mut label_ids = vec![-100i16; context.max_length];

    input_ids[0] = context.vocab.cls_id;
    attention_mask[0] = 1;
    let available = context.max_length.saturating_sub(2);
    let token_count = tokens.len().min(labels.len()).min(available);
    for idx in 0..token_count {
        input_ids[idx + 1] = token_id(&context.vocab, &tokens[idx]);
        attention_mask[idx + 1] = 1;
        let label = canonical_bio_label(&labels[idx]);
        label_ids[idx + 1] = context
            .label_ids
            .get(&label)
            .copied()
            .with_context(|| format!("unknown label '{label}'"))?;
    }
    let sep_pos = token_count + 1;
    input_ids[sep_pos] = context.vocab.sep_id;
    attention_mask[sep_pos] = 1;
    Ok((input_ids, attention_mask, label_ids))
}

fn labels_for_char_tokenizer(row: &SourceRow) -> (Vec<String>, Vec<String>) {
    if row.tokenizer_variant.as_deref() == Some("char") {
        if let Some(filename) = row.filename.as_deref() {
            let filename_chars = chars_as_strings(filename);
            if row.tokens == filename_chars {
                return (row.tokens.clone(), row.labels.clone());
            }
        }
    }

    if let Some(filename) = row.filename.as_deref() {
        if let Some(projected) = project_labels_from_filename(filename, &row.tokens, &row.labels) {
            let (tokens, mut labels) = projected;
            repair_structural_meta_labels(filename, &mut labels);
            return (tokens, labels);
        }
    }

    let (tokens, mut labels) = align_tokens_to_chars(&row.tokens, &row.labels);
    if let Some(filename) = row.filename.as_deref() {
        repair_structural_meta_labels(filename, &mut labels);
    }
    (tokens, labels)
}

fn project_labels_from_filename(
    filename: &str,
    source_tokens: &[String],
    source_labels: &[String],
) -> Option<(Vec<String>, Vec<String>)> {
    let offsets = token_offsets_in_text(filename, source_tokens)?;
    if offsets.len() != source_labels.len() {
        return None;
    }
    let char_len = filename.chars().count();
    let mut char_entities: Vec<Option<String>> = vec![None; char_len];
    for ((token, label), (mut start, mut end)) in source_tokens
        .iter()
        .zip(source_labels.iter())
        .zip(offsets.into_iter())
    {
        let Some(entity) = bio_entity(label) else {
            continue;
        };
        if is_wrapped_token(token) && end > start + 1 {
            start += 1;
            end -= 1;
        }
        for pos in start..end.min(char_entities.len()) {
            char_entities[pos] = Some(entity.clone());
        }
    }

    let tokens = chars_as_strings(filename);
    let mut labels = Vec::with_capacity(tokens.len());
    let mut active_entity: Option<String> = None;
    for entity in char_entities {
        match entity {
            Some(entity) => {
                let prefix = if active_entity.as_deref() == Some(entity.as_str()) {
                    "I"
                } else {
                    "B"
                };
                labels.push(format!("{prefix}-{entity}"));
                active_entity = Some(entity);
            }
            None => {
                labels.push("O".to_string());
                active_entity = None;
            }
        }
    }
    Some((tokens, labels))
}

fn token_offsets_in_text(text: &str, tokens: &[String]) -> Option<Vec<(usize, usize)>> {
    let mut offsets = Vec::with_capacity(tokens.len());
    let mut cursor = 0usize;
    for token in tokens {
        if token.is_empty() {
            let char_cursor = char_index_at_byte(text, cursor);
            offsets.push((char_cursor, char_cursor));
            continue;
        }
        let relative = text.get(cursor..)?.find(token)?;
        let start_byte = cursor + relative;
        let end_byte = start_byte + token.len();
        offsets.push((
            char_index_at_byte(text, start_byte),
            char_index_at_byte(text, end_byte),
        ));
        cursor = end_byte;
    }
    Some(offsets)
}

fn align_tokens_to_chars(tokens: &[String], labels: &[String]) -> (Vec<String>, Vec<String>) {
    let mut char_tokens = Vec::new();
    let mut char_labels = Vec::new();
    for (token, label) in tokens.iter().zip(labels.iter()) {
        let chars = chars_as_strings(token);
        if chars.is_empty() {
            continue;
        }
        let label = label.as_str();
        if label.starts_with("B-") {
            let entity = label
                .split_once('-')
                .map(|(_, entity)| entity)
                .unwrap_or("");
            char_labels.push(label.to_string());
            char_labels.extend((1..chars.len()).map(|_| format!("I-{entity}")));
        } else if label.starts_with("I-") {
            char_labels.extend((0..chars.len()).map(|_| label.to_string()));
        } else {
            char_labels.extend((0..chars.len()).map(|_| label.to_string()));
        }
        char_tokens.extend(chars);
    }
    (char_tokens, char_labels)
}

fn repair_structural_meta_labels(text: &str, labels: &mut [String]) {
    if labels.len() != text.chars().count() {
        return;
    }
    let episode_end = first_episode_span_end(labels);
    for (inner_start, inner_end) in bracket_inner_spans(text) {
        let bracket_start = inner_start.saturating_sub(1);
        if bracket_start < episode_end {
            continue;
        }
        let inner = chars_range_to_string(text, inner_start, inner_end);
        let (trim_start, trim_end) = trimmed_bounds(&inner);
        if trim_start >= trim_end {
            continue;
        }
        let clean = chars_slice_to_string(&inner, trim_start, trim_end);
        let clean_start = inner_start + trim_start;
        let clean_end = inner_start + trim_end;

        if special_tag_re().is_match(&clean) || special_code_re().is_match(&clean) {
            label_span_if_safe(labels, clean_start, clean_end, "SPECIAL");
            continue;
        }
        if source_tag_re().is_match(&clean) {
            label_span_if_safe(labels, clean_start, clean_end, "SOURCE");
            continue;
        }

        for mat in resolution_re().find_iter(&inner) {
            if !has_ascii_token_boundaries(&inner, mat.start(), mat.end()) {
                continue;
            }
            let start = inner_start + char_index_at_byte(&inner, mat.start());
            let end = inner_start + char_index_at_byte(&inner, mat.end());
            label_span_if_safe(labels, start, end, "RESOLUTION");
        }
        for mat in source_re().find_iter(&inner) {
            if !has_ascii_token_boundaries(&inner, mat.start(), mat.end()) {
                continue;
            }
            let start = inner_start + char_index_at_byte(&inner, mat.start());
            let end = inner_start + char_index_at_byte(&inner, mat.end());
            label_span_if_safe(labels, start, end, "SOURCE");
        }
    }

    for mat in resolution_re().find_iter(text) {
        if !has_ascii_token_boundaries(text, mat.start(), mat.end()) {
            continue;
        }
        let start = char_index_at_byte(text, mat.start());
        if start < episode_end {
            continue;
        }
        let end = char_index_at_byte(text, mat.end());
        label_span_if_safe(labels, start, end, "RESOLUTION");
    }
    for mat in source_re().find_iter(text) {
        if !has_ascii_token_boundaries(text, mat.start(), mat.end()) {
            continue;
        }
        let start = char_index_at_byte(text, mat.start());
        if start < episode_end {
            continue;
        }
        let end = char_index_at_byte(text, mat.end());
        label_span_if_safe(labels, start, end, "SOURCE");
    }
}

fn first_episode_span_end(labels: &[String]) -> usize {
    let mut idx = 0usize;
    while idx < labels.len() {
        if label_entity(&labels[idx]) == Some("EPISODE") {
            let mut end = idx + 1;
            while end < labels.len() && label_entity(&labels[end]) == Some("EPISODE") {
                end += 1;
            }
            return end;
        }
        idx += 1;
    }
    0
}

fn bracket_inner_spans(text: &str) -> Vec<(usize, usize)> {
    let chars = text.chars().collect::<Vec<_>>();
    let mut spans = Vec::new();
    let mut idx = 0usize;
    while idx < chars.len() {
        let close = match chars[idx] {
            '[' => ']',
            '(' => ')',
            '【' => '】',
            '《' => '》',
            _ => {
                idx += 1;
                continue;
            }
        };
        if let Some(relative_end) = chars[idx + 1..].iter().position(|ch| *ch == close) {
            let end = idx + 1 + relative_end;
            spans.push((idx + 1, end));
            idx = end + 1;
        } else {
            idx += 1;
        }
    }
    spans
}

fn trimmed_bounds(text: &str) -> (usize, usize) {
    let chars = text.chars().collect::<Vec<_>>();
    let mut start = 0usize;
    let mut end = chars.len();
    while start < end && chars[start].is_whitespace() {
        start += 1;
    }
    while end > start && chars[end - 1].is_whitespace() {
        end -= 1;
    }
    (start, end)
}

fn chars_range_to_string(text: &str, start: usize, end: usize) -> String {
    text.chars()
        .skip(start)
        .take(end.saturating_sub(start))
        .collect()
}

fn chars_slice_to_string(text: &str, start: usize, end: usize) -> String {
    text.chars()
        .skip(start)
        .take(end.saturating_sub(start))
        .collect()
}

fn label_span_if_safe(labels: &mut [String], start: usize, end: usize, entity: &str) {
    if start >= end || end > labels.len() {
        return;
    }
    if labels[start..end].iter().any(|label| {
        matches!(
            label_entity(label),
            Some("GROUP" | "EPISODE" | "SEASON" | "PATH_SEASON")
        )
    }) {
        return;
    }
    let previous_same = start > 0 && label_entity(&labels[start - 1]) == Some(entity);
    let mut first = !previous_same;
    for label in labels.iter_mut().take(end).skip(start) {
        *label = if first {
            format!("B-{entity}")
        } else {
            format!("I-{entity}")
        };
        first = false;
    }
}

fn has_ascii_token_boundaries(text: &str, start: usize, end: usize) -> bool {
    let previous_ok = text[..start]
        .chars()
        .next_back()
        .map(|ch| !ch.is_ascii_alphanumeric())
        .unwrap_or(true);
    let next_ok = text[end..]
        .chars()
        .next()
        .map(|ch| !ch.is_ascii_alphanumeric())
        .unwrap_or(true);
    previous_ok && next_ok
}

fn label_entity(label: &str) -> Option<&str> {
    let (prefix, entity) = label.split_once('-')?;
    if prefix == "B" || prefix == "I" {
        Some(entity)
    } else {
        None
    }
}

fn resolution_re() -> &'static Regex {
    RESOLUTION_RE
        .get_or_init(|| Regex::new(r"(?i)(?:\d{3,4}p|\d[kK]|\d{3,4}[xX×]\d{3,4})").unwrap())
}

fn source_re() -> &'static Regex {
    SOURCE_RE.get_or_init(|| Regex::new(&format!(r"(?i)(?:{SOURCE_TOKEN_PATTERN})")).unwrap())
}

fn source_tag_re() -> &'static Regex {
    SOURCE_TAG_RE.get_or_init(|| {
        Regex::new(&format!(
            r"(?i)^(?:{SOURCE_TOKEN_PATTERN})(?:\s*(?:[&+/,_-]|,\s*)\s*(?:{SOURCE_TOKEN_PATTERN}))*$"
        ))
        .unwrap()
    })
}

fn special_tag_re() -> &'static Regex {
    SPECIAL_TAG_RE.get_or_init(|| {
        Regex::new(r"(?i)^(?:檢索|检索|搜索|搜寻|搜尋|别名|別名|alias|search|keyword)\s*[:：].+")
            .unwrap()
    })
}

fn special_code_re() -> &'static Regex {
    SPECIAL_CODE_RE.get_or_init(|| {
        Regex::new(r"(?i)^(?:NCOP|NCED|OP|ED|PV|CM)\d*$|^IV\d+$|^(?:OVA|OAD|SP)\d*$").unwrap()
    })
}

fn chars_as_strings(text: &str) -> Vec<String> {
    text.chars().map(|ch| ch.to_string()).collect()
}

fn char_index_at_byte(text: &str, byte_index: usize) -> usize {
    text[..byte_index].chars().count()
}

fn bio_entity(label: &str) -> Option<String> {
    let (prefix, entity) = label.split_once('-')?;
    if prefix == "B" || prefix == "I" {
        Some(entity.to_string())
    } else {
        None
    }
}

fn is_wrapped_token(token: &str) -> bool {
    let mut chars = token.chars();
    let Some(first) = chars.next() else {
        return false;
    };
    let Some(last) = token.chars().last() else {
        return false;
    };
    matches!(first, '[' | '【' | '(' | '《') && matches!(last, ']' | '】' | ')' | '》')
}

fn canonical_bio_label(label: &str) -> String {
    let Some((prefix, entity)) = label.split_once('-') else {
        return if label == "O" {
            "O".to_string()
        } else {
            label.to_string()
        };
    };
    if prefix != "B" && prefix != "I" {
        return label.to_string();
    }
    let canonical_entity = match entity {
        "TITLE" => "TITLE_MIXED",
        "PATH_TITLE" => "PATH_TITLE_MIXED",
        other => other,
    };
    format!("{prefix}-{canonical_entity}")
}

fn token_id(vocab: &Vocab, token: &str) -> u16 {
    *vocab.ids.get(token).unwrap_or(&vocab.unk_id)
}

fn write_eval_records(rows: &[SourceRow], path: &Path) -> Result<()> {
    let mut writer = BufWriter::new(
        File::create(path).with_context(|| format!("failed to create {}", path.display()))?,
    );
    for row in rows {
        writer.write_all(row.raw_line.as_bytes())?;
        writer.write_all(b"\n")?;
    }
    Ok(())
}

fn write_npy_u16(path: &Path, data: &[u16], rows: usize, cols: usize) -> Result<()> {
    let mut writer = BufWriter::new(
        File::create(path).with_context(|| format!("failed to create {}", path.display()))?,
    );
    write_npy_header(&mut writer, "<u2", rows, cols)?;
    for value in data {
        writer.write_all(&value.to_le_bytes())?;
    }
    Ok(())
}

fn write_npy_u8(path: &Path, data: &[u8], rows: usize, cols: usize) -> Result<()> {
    let mut writer = BufWriter::new(
        File::create(path).with_context(|| format!("failed to create {}", path.display()))?,
    );
    write_npy_header(&mut writer, "|u1", rows, cols)?;
    writer.write_all(data)?;
    Ok(())
}

fn write_npy_i16(path: &Path, data: &[i16], rows: usize, cols: usize) -> Result<()> {
    let mut writer = BufWriter::new(
        File::create(path).with_context(|| format!("failed to create {}", path.display()))?,
    );
    write_npy_header(&mut writer, "<i2", rows, cols)?;
    for value in data {
        writer.write_all(&value.to_le_bytes())?;
    }
    Ok(())
}

fn write_npy_header<W: Write>(writer: &mut W, descr: &str, rows: usize, cols: usize) -> Result<()> {
    let mut header = format!(
        "{{'descr': '{}', 'fortran_order': False, 'shape': ({}, {}), }}",
        descr, rows, cols
    )
    .into_bytes();
    let preamble_len = 10usize;
    let pad_len = (16 - ((preamble_len + header.len() + 1) % 16)) % 16;
    header.extend(std::iter::repeat(b' ').take(pad_len));
    header.push(b'\n');
    if header.len() > u16::MAX as usize {
        bail!("npy header too large");
    }
    writer.write_all(b"\x93NUMPY")?;
    writer.write_all(&[1, 0])?;
    writer.write_all(&(header.len() as u16).to_le_bytes())?;
    writer.write_all(&header)?;
    Ok(())
}