"""
Redshift — Lineage Collection (collect-only)
==============================================
Collects table-level lineage from Redshift by fetching recent successful query
history from sys_query_history + sys_querytext and parsing CREATE TABLE AS SELECT
(CTAS) and INSERT INTO SELECT patterns to derive source->destination relationships.

Writes a JSON manifest file that can be consumed by push_lineage.py.

Substitution points (search for "← SUBSTITUTE"):
  - REDSHIFT_HOST / REDSHIFT_DB / REDSHIFT_USER / REDSHIFT_PASSWORD : connection
  - LOOKBACK_HOURS    : how far back to scan query history (default 24 h)

Prerequisites:
  pip install psycopg2-binary
"""

from __future__ import annotations

import argparse
import ipaddress
import json
import logging
import os
import re
from datetime import datetime, timezone
from typing import Any

import psycopg2
from _safe_paths import safe_existing_directory, safe_input_json_path, safe_output_json_path, write_json_file

logging.basicConfig(level=logging.INFO, format="%(asctime)s %(levelname)s %(message)s")
log = logging.getLogger(__name__)

RESOURCE_TYPE = "redshift"
LOOKBACK_HOURS: int = int(os.getenv("LOOKBACK_HOURS", "24"))  # ← SUBSTITUTE

_ALLOWED_REDSHIFT_HOST_RE = re.compile(
    r"^[a-z0-9][a-z0-9.-]*\.(?:redshift|redshift-serverless)\.[a-z0-9-]+\.amazonaws\.com(?:\.cn)?$",
    re.IGNORECASE,
)


def _explicitly_allowed_redshift_hosts() -> set[str]:
    raw_hosts = os.getenv("REDSHIFT_ALLOWED_HOSTS", "")
    return {host.strip().lower().rstrip(".") for host in raw_hosts.split(",") if host.strip()}


def validate_redshift_host(host: str, *, allow_private: bool = False) -> str:
    value = str(host).strip()
    if not value or any(part in value for part in ("/", "\\", "@", ":")):
        raise ValueError(f"Invalid Redshift host: {host!r}")
    hostname = value.lower().rstrip(".")
    allowed_hosts = _explicitly_allowed_redshift_hosts()
    try:
        address = ipaddress.ip_address(value)
    except ValueError:
        if hostname in allowed_hosts:
            return hostname
        match = _ALLOWED_REDSHIFT_HOST_RE.fullmatch(hostname)
        if match:
            return match.group(0)
        raise ValueError(
            "Redshift host must be an AWS Redshift endpoint or be listed in REDSHIFT_ALLOWED_HOSTS"
        )
    if hostname not in allowed_hosts:
        raise ValueError("Redshift IP hosts must be listed in REDSHIFT_ALLOWED_HOSTS")
    blocked = (
        address.is_loopback
        or address.is_link_local
        or address.is_multicast
        or address.is_unspecified
        or address.is_reserved
        or (address.is_private and not allow_private)
    )
    if blocked:
        raise ValueError(f"Redshift host address is not allowed: {host!r}")
    return str(address)


def _bounded_int(value: int, field: str, *, minimum: int, maximum: int) -> int:
    value = int(value)
    if value < minimum or value > maximum:
        raise ValueError(f"{field} must be between {minimum} and {maximum}")
    return value


def _check_available_memory(min_gb: float = 2.0) -> None:
    """Warn if available memory is below the threshold."""
    try:
        if hasattr(os, "sysconf"):  # Linux / macOS
            page_size = os.sysconf("SC_PAGE_SIZE")
            avail_pages = os.sysconf("SC_AVPHYS_PAGES")
            avail_gb = (page_size * avail_pages) / (1024 ** 3)
        else:
            return  # Windows — skip check
    except (ValueError, OSError):
        return
    if avail_gb < min_gb:
        log.warning(
            "Only %.1f GB of memory available (minimum recommended: %.1f GB). "
            "Consider reducing the collection scope or increasing available memory.",
            avail_gb,
            min_gb,
        )


# Regex: CTAS — CREATE [OR REPLACE] TABLE <dest> AS SELECT
_CTAS_RE = re.compile(
    r"CREATE\s+(?:OR\s+REPLACE\s+)?(?:TABLE|VIEW)\s+(?P<dest>\"?[\w.\"]+\"?)\s*(?:\([^)]*\))?\s*AS\s+SELECT\b",
    re.IGNORECASE | re.DOTALL,
)
# Regex: INSERT INTO <dest> … SELECT
_INSERT_RE = re.compile(
    r"INSERT\s+INTO\s+(?P<dest>\"?[\w.\"]+\"?)\s.*?SELECT\b",
    re.IGNORECASE | re.DOTALL,
)
# Matches any schema.table or database.schema.table reference in the query
_TABLE_REF_RE = re.compile(r'"?([\w]+)"?\."?([\w]+)"?(?:\."?([\w]+)"?)?', re.IGNORECASE)


def _clean_name(name: str) -> str:
    return name.strip('"').strip()


def _parse_ref(ref: str) -> tuple[str, str, str]:
    """Parse 'db.schema.table' or 'schema.table' -> (database, schema, table)."""
    parts = [_clean_name(p) for p in ref.split(".")]
    if len(parts) == 3:
        return parts[0], parts[1], parts[2]
    if len(parts) == 2:
        return "", parts[0], parts[1]
    return "", "", parts[0]


def _dictfetch(cursor: Any, sql: str, params: tuple | None = None) -> list[dict[str, Any]]:
    cursor.execute(sql, params)
    cols = [d.name for d in cursor.description]
    rows = []
    while True:
        chunk = cursor.fetchmany(1000)
        if not chunk:
            break
        rows.extend(dict(zip(cols, row)) for row in chunk)
    return rows


def fetch_query_texts(cursor: Any, lookback_hours: int) -> list[str]:
    """Assemble full query texts from sys_query_history + sys_querytext."""
    lookback_hours = _bounded_int(lookback_hours, "lookback_hours", minimum=1, maximum=24 * 31)
    rows = _dictfetch(
        cursor,
        """
        SELECT
            sq.query_id,
            LISTAGG(
                CASE WHEN LEN(st.text) <= 200 THEN st.text ELSE LEFT(st.text, 200) END,
                ''
            ) WITHIN GROUP (ORDER BY st.sequence) AS full_text
        FROM sys_query_history sq
        JOIN sys_querytext st ON sq.query_id = st.query_id
        WHERE sq.start_time >= DATEADD(hour, -%s, GETDATE())
          AND sq.status = 'success'
        GROUP BY sq.query_id
        LIMIT 50000
        """,  # ← SUBSTITUTE: adjust lookback_hours, LIMIT, or add user/database filters
        (lookback_hours,),
    )
    return [r["full_text"] for r in rows if r.get("full_text")]


def parse_lineage_from_sql(sql_text: str) -> list[dict[str, Any]]:
    events: list[dict[str, Any]] = []

    dest_match = _CTAS_RE.search(sql_text) or _INSERT_RE.search(sql_text)
    if not dest_match:
        return events

    dest_raw = dest_match.group("dest")
    dest_db, dest_schema, dest_table = _parse_ref(dest_raw)
    if not dest_table:
        return events

    # Find all schema.table refs in the query, excluding the destination
    source_refs: list[str] = []
    for m in _TABLE_REF_RE.finditer(sql_text):
        if m.group(3):
            ref = f"{m.group(1)}.{m.group(2)}.{m.group(3)}"
        else:
            ref = f"{m.group(1)}.{m.group(2)}"

        db, schema, table = _parse_ref(ref)
        if not table or (db == dest_db and schema == dest_schema and table == dest_table):
            continue
        source_refs.append(ref)

    if not source_refs:
        return events

    # Deduplicate sources while preserving order
    seen: set[str] = set()
    sources: list[dict[str, str]] = []
    for ref in source_refs:
        if ref not in seen:
            seen.add(ref)
            db, schema, table = _parse_ref(ref)
            sources.append({"database": db, "schema": schema, "asset_name": table})

    events.append({
        "sources": sources,
        "destination": {"database": dest_db, "schema": dest_schema, "asset_name": dest_table},
    })
    return events


def collect(
    host: str,
    db: str,
    user: str,
    password: str,
    manifest_path: str = "manifest_lineage.json",
    port: int = 5439,
    lookback_hours: int = LOOKBACK_HOURS,
) -> list[dict[str, Any]]:
    """Connect to Redshift, collect lineage, write a JSON manifest, and return events."""
    _check_available_memory()
    allow_private_host = os.getenv("REDSHIFT_ALLOW_PRIVATE_HOST", "").lower() in {"1", "true", "yes"}
    host = validate_redshift_host(host, allow_private=allow_private_host)
    port = _bounded_int(port, "port", minimum=1, maximum=65535)
    lookback_hours = _bounded_int(lookback_hours, "lookback_hours", minimum=1, maximum=24 * 31)
    collected_at = datetime.now(timezone.utc).isoformat()

    conn = psycopg2.connect(
        host=host, port=port, dbname=db, user=user, password=password, connect_timeout=30,
    )
    try:
        with conn.cursor() as cursor:
            query_texts = fetch_query_texts(cursor, lookback_hours)
    finally:
        conn.close()

    log.info("Parsing lineage from %d query texts …", len(query_texts))
    all_events: list[dict[str, Any]] = []
    for sql_text in query_texts:
        all_events.extend(parse_lineage_from_sql(sql_text))

    log.info("Collected %d lineage events", len(all_events))

    manifest = {
        "resource_type": RESOURCE_TYPE,
        "collected_at": collected_at,
        "lookback_hours": lookback_hours,
        "queries_scanned": len(query_texts),
        "lineage_event_count": len(all_events),
        "events": all_events,
    }
    write_json_file(manifest_path, manifest)
    log.info("Manifest written to %s (%d events)", manifest_path, len(all_events))

    return all_events


def main() -> None:
    parser = argparse.ArgumentParser(description="Collect Redshift lineage to a manifest file")
    parser.add_argument("--db", default=os.getenv("REDSHIFT_DB"))             # ← SUBSTITUTE
    parser.add_argument("--user", default=os.getenv("REDSHIFT_USER"))         # ← SUBSTITUTE
    parser.add_argument("--password", default=os.getenv("REDSHIFT_PASSWORD")) # ← SUBSTITUTE
    parser.add_argument("--port", type=int, default=int(os.getenv("REDSHIFT_PORT", "5439")))
    parser.add_argument("--lookback-hours", type=int, default=LOOKBACK_HOURS)
    parser.add_argument("--manifest", default="manifest_lineage.json")
    args = parser.parse_args()

    required = ["db", "user", "password"]
    missing = [k for k in required if getattr(args, k) is None]
    if missing:
        parser.error(f"Missing required arguments/env vars: {missing}")

    redshift_host = os.getenv("REDSHIFT_HOST")
    if not redshift_host:
        parser.error("Missing required env var: REDSHIFT_HOST")
    redshift_host = validate_redshift_host(
        redshift_host,
        allow_private=os.getenv("REDSHIFT_ALLOW_PRIVATE_HOST", "").lower() in {"1", "true", "yes"},
    )

    collect(
        host=redshift_host,
        db=args.db,
        user=args.user,
        password=args.password,
        manifest_path=args.manifest,
        port=args.port,
        lookback_hours=args.lookback_hours,
    )


if __name__ == "__main__":
    main()