#!/usr/bin/env python3
"""
chunk_docs.py — section-aware chunking of the fetched CDS/ADS/EWDS deep docs.

Mirrors eqc_qa/chunk_reports.py. One chunk-set per UNIQUE doc (a doc shared by
several datasets is chunked once; its chunks carry dataset_ids[] = all datasets
that reference it, so the server can filter per dataset).

Input : deep_docs/manifest.jsonl (status==ok rows) + their parsed/*.md
Output: deep_docs/chunks.jsonl — payload:
  chunk_id, doc_url, doc_title, doc_kind, dataset_ids[], store, stores[],
  section, chunk_index, token_count, text_raw, text_with_prefix
"""
import hashlib
import json
import re
import sys
from pathlib import Path

import tiktoken

ROOT = Path(__file__).resolve().parent.parent
MANIFEST = ROOT / "deep_docs" / "manifest.jsonl"
OUT = ROOT / "deep_docs" / "chunks.jsonl"
META = ROOT / "meta_harvest" / "unified_metadata.json"

MAX_TOKENS = 1000
MIN_QUALITY_TOKENS = 30
MIN_TOKENS = 80
OVERLAP_RATIO = 0.05
_enc = tiktoken.get_encoding("cl100k_base")


def log(*a):
    print(*a, file=sys.stderr, flush=True)


def count_tokens(t): return len(_enc.encode(t))


HEADING = re.compile(r"^(#{1,4})\s+(.*)$")


def parse_sections(md):
    lines = md.splitlines()
    stack, cur_path, buf, sections, in_fence = [], "[intro]", [], [], False

    def flush():
        body = "\n".join(buf).strip()
        if body:
            sections.append((cur_path, body))
    for ln in lines:
        if ln.lstrip().startswith("```"):
            in_fence = not in_fence; buf.append(ln); continue
        m = None if in_fence else HEADING.match(ln)
        if m:
            flush(); buf = []
            level = len(m.group(1))
            title = re.sub(r"[#*`]", "", m.group(2)).strip()
            while stack and stack[-1][0] >= level:
                stack.pop()
            stack.append((level, title))
            cur_path = " > ".join(t for _, t in stack) or "[section]"
        else:
            buf.append(ln)
    flush()
    return sections


def split_by_tokens(text, max_tokens):
    paras = re.split(r"\n\s*\n", text)
    chunks, cur, cur_tok = [], [], 0
    for p in paras:
        p = p.strip()
        if not p:
            continue
        pt = count_tokens(p)
        if pt > max_tokens:
            if cur:
                chunks.append("\n\n".join(cur)); cur, cur_tok = [], 0
            ids = _enc.encode(p)
            for i in range(0, len(ids), max_tokens):
                chunks.append(_enc.decode(ids[i:i + max_tokens]))
            continue
        if cur_tok + pt > max_tokens and cur:
            chunks.append("\n\n".join(cur)); cur, cur_tok = [], 0
        cur.append(p); cur_tok += pt
    if cur:
        chunks.append("\n\n".join(cur))
    return chunks


def add_overlap(chunks, ratio):
    if len(chunks) < 2 or ratio <= 0:
        return chunks
    out = [chunks[0]]
    for i in range(1, len(chunks)):
        ptoks = _enc.encode(chunks[i - 1])
        n = max(1, int(len(ptoks) * ratio))
        out.append(_enc.decode(ptoks[-n:]) + "\n\n" + chunks[i])
    return out


def main():
    meta = json.loads(META.read_text()) if META.exists() else {}
    store_of = {}
    for k, v in meta.items():
        pid = v.get("product_id") or k
        store_of[pid] = (v.get("store") or "").upper()

    recs = [json.loads(l) for l in MANIFEST.read_text().splitlines() if l.strip()]
    ok = [r for r in recs if r["status"] == "ok" and r.get("md_path")]
    # dedup by url
    seen_url = {}
    for r in ok:
        seen_url[r["url"]] = r
    log(f"chunking {len(seen_url)} unique docs")

    n_docs = n_chunks = 0
    with open(OUT, "w", encoding="utf-8") as f:
        for url, r in seen_url.items():
            p = ROOT / r["md_path"]
            if not p.exists():
                continue
            md = p.read_text(encoding="utf-8", errors="replace")
            dsids = sorted(set(r["datasets"]))
            stores = sorted({store_of.get(d, "") for d in dsids} - {""})
            store = stores[0] if stores else "CDS"
            title = r.get("title") or ""
            counter = 0
            seen_h = set()
            for section, body in parse_sections(md):
                body = re.sub(r"\n{3,}", "\n\n", body).strip()
                if not body:
                    continue
                raw = split_by_tokens(body, MAX_TOKENS)
                if len(raw) > 1:
                    raw = add_overlap(raw, OVERLAP_RATIO)
                for ct in raw:
                    ct = ct.strip()
                    if count_tokens(ct) < MIN_QUALITY_TOKENS:
                        continue
                    h = hashlib.md5(ct.encode()).hexdigest()
                    if h in seen_h:
                        continue
                    seen_h.add(h)
                    prefix = (f'Copernicus documentation: "{title}"\n'
                              f'Dataset(s): {", ".join(dsids[:6])} [{store}]\n'
                              f'Section: {section}\n---\n')
                    twp = prefix + ct
                    f.write(json.dumps({
                        "chunk_id": f"{hashlib.md5(url.encode()).hexdigest()[:12]}__{h[:12]}",
                        "doc_url": url,
                        "doc_title": title,
                        "doc_kind": r.get("kind"),
                        "dataset_ids": dsids,
                        "store": store,
                        "stores": stores,
                        "doc_type": "DEEP_DOC",
                        "section": section,
                        "chunk_index": counter,
                        "token_count": count_tokens(twp),
                        "text_raw": ct,
                        "text_with_prefix": twp,
                    }, ensure_ascii=False) + "\n")
                    counter += 1
            n_docs += 1
            n_chunks += counter
    toks = sum(json.loads(l)["token_count"] for l in open(OUT))
    log(f"DONE: {n_docs} docs -> {n_chunks} chunks ({toks:,} tokens) -> {OUT}")
    log(f"est batch embed ${toks/1e6*0.125:.2f} (realtime ${toks/1e6*0.25:.2f})")


if __name__ == "__main__":
    main()