import datetime
from typing import List, Dict, Tuple

import pytz
from langchain.tools import tool  # or whatever decorator you use

# ────────────────────────────────────────────────────────────────────────────
# 1️⃣  Keep your existing helper (unchanged)
# ────────────────────────────────────────────────────────────────────────────
@tool
def get_current_time_in_timezone(timezone: str) -> str:
    """Return the current local time in a given timezone (YYYY-MM-DD HH:MM:SS)."""
    try:
        tz = pytz.timezone(timezone)
        local_time = datetime.datetime.now(tz).strftime("%Y-%m-%d %H:%M:%S")
        return local_time
    except Exception as e:
        return f"Error: {e}"

# ────────────────────────────────────────────────────────────────────────────
# 2️⃣  New tool: find the first 30-minute slot that fits everyone’s workday
# ────────────────────────────────────────────────────────────────────────────
@tool
def find_overlap_slot(
    timezones: List[str],
    workday_start: int = 9,
    workday_end: int = 18,
    slot_minutes: int = 30
) -> str:
    """
    Find the next common slot for a stand-up.
    
    Args:
        timezones: List of IANA tz strings (e.g. ["Europe/Berlin", "Asia/Bishkek"])
        workday_start: Local workday start hour (24h clock, default 09)
        workday_end:   Local workday end hour   (default 18)
        slot_minutes:  Length of slot to find   (default 30)
    Returns:
        Human-readable description of the first viable slot, or error msg.
    """
    # 1. Build a list of "free intervals" for each participant
    now_utc = datetime.datetime.utcnow().replace(tzinfo=pytz.utc)
    candidates: List[Tuple[datetime.datetime, datetime.datetime]] = []

    for tz_name in timezones:
        try:
            tz = pytz.timezone(tz_name)
        except pytz.UnknownTimeZoneError:
            return f"Unknown timezone: {tz_name}"

        local_now = now_utc.astimezone(tz)
        # Next work-day window
        start_local = local_now.replace(hour=workday_start, minute=0, second=0, microsecond=0)
        end_local   = local_now.replace(hour=workday_end,   minute=0, second=0, microsecond=0)
        if local_now > end_local:
            # Move to tomorrow
            start_local += datetime.timedelta(days=1)
            end_local   += datetime.timedelta(days=1)
        elif local_now > start_local:
            # Move start forward so we don't schedule in the past
            start_local = local_now

        # Convert to UTC for overlap maths
        candidates.append((
            start_local.astimezone(pytz.utc),
            end_local.astimezone(pytz.utc)
        ))

    # 2. Intersect all availability windows
    slot_start = max(interval[0] for interval in candidates)
    slot_end   = min(interval[1] for interval in candidates)

    if slot_end - slot_start < datetime.timedelta(minutes=slot_minutes):
        return "No overlapping work-hour slot found in the next day."

    # 3. Return the first slot of the requested length
    chosen_start = slot_start
    chosen_end   = slot_start + datetime.timedelta(minutes=slot_minutes)

    # 4. Build a friendly summary
    summary_lines = [
        f"✅ Proposed stand-up slot ({slot_minutes} min)",
        f"    • UTC: {chosen_start.strftime('%Y-%m-%d %H:%M')} – {chosen_end.strftime('%H:%M')}"
    ]
    for tz_name in timezones:
        tz = pytz.timezone(tz_name)
        loc_start = chosen_start.astimezone(tz).strftime('%Y-%m-%d %H:%M')
        loc_end   = chosen_end.astimezone(tz).strftime('%H:%M')
        summary_lines.append(f"    • {tz_name}: {loc_start} – {loc_end}")

    return "\n".join(summary_lines)

# ────────────────────────────────────────────────────────────────────────────
# 3️⃣  Example of an empty placeholder tool you can extend later
# ────────────────────────────────────────────────────────────────────────────
@tool
def my_custom_tool(arg1: str, arg2: int) -> str:
    """A template tool you can repurpose for anything."""
    return f"Received arg1={arg1}, arg2={arg2}. What magic will you build?"