import csv, io, re, calendar
from datetime import datetime, timedelta, date
from dateutil import parser as dateparser
from collections import Counter, defaultdict
from django.db.models.functions import TruncMonth
from django.db.models import Count
from .models import Entry, ScriptureRef

BOOK_ALIASES = {
    "gen": "Genesis","ex": "Exodus","lev": "Leviticus","num": "Numbers","deut": "Deuteronomy",
    "josh": "Joshua","judg":"Judges","rut":"Ruth","1sam":"1 Samuel","2sam":"2 Samuel",
    "1kings":"1 Kings","2kings":"2 Kings","1chron":"1 Chronicles","2chron":"2 Chronicles",
    "ezra":"Ezra","neh":"Nehemiah","esth":"Esther","job":"Job","ps":"Psalms","prov":"Proverbs",
    "eccl":"Ecclesiastes","song":"Song of Solomon","isa":"Isaiah","jer":"Jeremiah","lam":"Lamentations",
    "ezek":"Ezekiel","dan":"Daniel","hos":"Hosea","joel":"Joel","amos":"Amos","obad":"Obadiah",
    "jon":"Jonah","mic":"Micah","nah":"Nahum","hab":"Habakkuk","zeph":"Zephaniah","hag":"Haggai",
    "zech":"Zechariah","mal":"Malachi","matt":"Matthew","mt":"Matthew","mark":"Mark","lk":"Luke",
    "luke":"Luke","jn":"John","john":"John","acts":"Acts","rom":"Romans","1cor":"1 Corinthians",
    "2cor":"2 Corinthians","gal":"Galatians","eph":"Ephesians","phil":"Philippians","col":"Colossians",
    "1thess":"1 Thessalonians","2thess":"2 Thessalonians","1tim":"1 Timothy","2tim":"2 Timothy",
    "titus":"Titus","phlm":"Philemon","heb":"Hebrews","jas":"James","1pet":"1 Peter","2pet":"2 Peter",
    "1john":"1 John","2john":"2 John","3john":"3 John","jude":"Jude","rev":"Revelation",
}

SCR_REF_RE = re.compile(r"""
    ^\s*([1-3]?\s*[A-Za-z\.]+)\s+
    (\d+)
    (?::(\d+))?
    (?:\s*[-–—]\s*(\d+)(?::(\d+))?)?
    \s*$
""", re.VERBOSE)

def normalize_book(book_raw:str) -> str:
    b = re.sub(r"[\.\s]","", book_raw).lower()
    return BOOK_ALIASES.get(b, book_raw.strip())

def parse_scripture(s: str):
    parts = [p.strip() for p in s.split(";") if p.strip()]
    parsed = []
    for p in parts:
        m = SCR_REF_RE.match(p)
        if not m:
            parsed.append(None)
            continue
        book_raw, ch1, v1, ch2, v2 = m.groups()
        parsed.append({
            "book": normalize_book(book_raw),
            "chapter_from": int(ch1),
            "verse_from": int(v1) if v1 else None,
            "chapter_to": int(ch2) if ch2 else None,
            "verse_to": int(v2) if v2 else None,
        })
    return parsed

def parse_date(value):
    if not value or not str(value).strip():
        return None
    try:
        d = dateparser.parse(str(value)).date()
        return d
    except Exception:
        return None

EXPECTED_HEADERS = [
    "subject","illustration","application","scripture","source","talk number",
    "talk title","code","date","date edited"
]

def import_csv_bytes(file_bytes: bytes, dry_run: bool=True):
    text = file_bytes.decode("utf-8-sig")
    reader = csv.DictReader(io.StringIO(text))
    headers = [h.strip().lower() for h in reader.fieldnames or []]
    missing = [h for h in EXPECTED_HEADERS if h not in headers]
    if missing:
        raise ValueError(f"Missing required headers: {missing}")
    report = {"rows": 0,"inserted": 0,"updated": 0,"skipped": 0,"errors": [],"scripture_parsed": 0,"scripture_failed": 0}
    rows = list(reader)
    report["rows"] = len(rows)

    for row in rows:
        try:
            entry_code = (row.get("code") or "").strip()
            talk_number = row.get("talk number")
            try:
                talk_number = int(talk_number) if str(talk_number).strip() else None
            except Exception:
                talk_number = None

            date_added = parse_date(row.get("date"))
            date_edited = parse_date(row.get("date edited"))

            data = dict(
                subject=row.get("subject") or "",
                illustration=row.get("illustration") or "",
                application=row.get("application") or "",
                scripture_raw=row.get("scripture") or "",
                source=row.get("source") or "",
                talk_number=talk_number,
                talk_title=row.get("talk title") or "",
                entry_code=entry_code,
                date_added=date_added,
                date_edited=date_edited,
            )

            from .models import Entry, ScriptureRef
            obj = None
            if entry_code:
                try:
                    obj = Entry.objects.get(entry_code=entry_code)
                except Entry.DoesNotExist:
                    obj = None

            # parse scriptures for reporting
            parsed_list = parse_scripture(data["scripture_raw"])
            for item in parsed_list:
                if item:
                    report["scripture_parsed"] += 1
                else:
                    report["scripture_failed"] += 1

            if not dry_run:
                if obj:
                    for k, v in data.items():
                        setattr(obj, k, v)
                    obj.save()
                    obj.scripture_refs.all().delete()
                    report["updated"] += 1
                else:
                    from .models import Entry
                    obj = Entry.objects.create(**data)
                    report["inserted"] += 1

                # persist parsed scripture refs
                for item in parsed_list:
                    if item:
                        ScriptureRef.objects.create(entry=obj, **item)

        except Exception as e:
            report["skipped"] += 1
            report["errors"].append(str(e))

    return report

def wildcard_to_like(q: str) -> str:
    # Convert * and ? to SQL LIKE wildcards
    return q.replace("%","\%").replace("_","\_").replace("*","%").replace("?","_")

def terms(q: str):
    return [t for t in q.split() if t.strip()]

def month_buckets_last_12(today: date):
    # returns list of (YYYY-MM, start, end)
    months = []
    y, m = today.year, today.month
    for i in range(12):
        mm = m - i
        yy = y
        while mm <= 0:
            mm += 12
            yy -= 1
        start = date(yy, mm, 1)
        if mm == 12:
            end = date(yy+1, 1, 1)
        else:
            end = date(yy, mm+1, 1)
        months.append((f"{yy}-{mm:02d}", start, end))
    return list(reversed(months))