"""
.agents/skills/lib_py/layout.py
Shared 2xK grid TUI layout engine for multi-agent workspaces.
"""
from dataclasses import dataclass
from typing import List, Dict, Optional, Any
import json
import sys
import os
import argparse


@dataclass
class PaneInfo:
    pane_id: str
    x: int
    y: int
    width: int
    height: int
    # NOTE: no `focused` field. The 2xK engine is deliberately geometry- and
    # structure-driven so that identical pane sets always yield identical
    # decisions. Focus is user-interaction state and would make the result
    # non-deterministic; herdr still reports it in the payload if ever needed.


@dataclass
class LayoutDecision:
    target_pane_id: str
    direction: str          # 'right' | 'down' | 'overflow'
    is_overflow: bool = False
    reason: str = ""


def extract_panes(data: Dict[str, Any]) -> List[PaneInfo]:
    """Extracts list of PaneInfo from herdr layout JSON payload.

    Accepts all three shapes herdr 0.8 emits: result.layout.panes,
    result.panes, and a bare top-level panes array.
    """
    if not isinstance(data, dict):
        return []

    res = data.get("result", {})
    if not isinstance(res, dict):
        res = {}

    layout = res.get("layout", {})
    if isinstance(layout, dict) and "panes" in layout:
        raw_panes = layout.get("panes", [])
    else:
        raw_panes = res.get("panes", []) or data.get("panes", [])

    panes: List[PaneInfo] = []
    for p in raw_panes:
        if not isinstance(p, dict):
            continue
        pid = str(p.get("pane_id", ""))
        rect = p.get("rect", {})
        if not isinstance(rect, dict):
            rect = {}
        x = int(rect.get("x", 0))
        y = int(rect.get("y", 0))
        w = int(rect.get("width", 0))
        h = int(rect.get("height", 0))
        if pid:
            panes.append(PaneInfo(pane_id=pid, x=x, y=y, width=w, height=h))

    return panes


def compute_2xk_layout(
    data: Dict[str, Any],
    min_cols: int = 40,
    min_rows: int = 20,
    max_columns: Optional[int] = None,
    default_anchor_id: Optional[str] = None
) -> LayoutDecision:
    """
    Computes optimal target pane and direction to maintain a balanced 2xK grid.
    Only uses Herdr-supported split directions: 'right' and 'down'.
    """
    panes = extract_panes(data)

    if not panes:
        # no_panes_default: when herdr returns no panes (empty workspace), default to 'right'
        target = default_anchor_id or ""
        return LayoutDecision(target_pane_id=target, direction="right", is_overflow=False, reason="no_panes_default")

    # If only 1 pane in workspace
    if len(panes) == 1:
        p = panes[0]
        # In 2xK grid, 1 pane -> 2 panes: split down to create top and bottom rows
        # Check height overflow if dimensions known
        if p.height > 0 and p.height // 2 < min_rows:
            # If height is too small for 2 rows, try splitting right if width allows
            if p.width > 0 and p.width // 2 >= min_cols:
                return LayoutDecision(target_pane_id=p.pane_id, direction="right", reason="single_pane_height_constrained")
            elif p.width > 0 and p.width // 2 < min_cols:
                return LayoutDecision(target_pane_id=p.pane_id, direction="overflow", is_overflow=True, reason="single_pane_overflow")
            else:
                return LayoutDecision(target_pane_id=p.pane_id, direction="right", reason="single_pane_height_constrained_unknown_width")
        return LayoutDecision(target_pane_id=p.pane_id, direction="down", reason="single_pane_split_down")

    # Check for Headless mode: all panes have width <= 0 or height <= 0
    is_headless = all(p.width <= 0 or p.height <= 0 for p in panes)
    if is_headless:
        # Headless panes are all 0x0, so columns cannot be counted from geometry
        # the way the GUI path does. The alternation below (odd -> down,
        # even -> right) is what builds the grid, so while that invariant holds
        # the completed-column count is exactly n // 2. If panes were closed and
        # the shape drifted, an odd n is absorbed by the `down` branch and the
        # estimate self-corrects at the next even n.
        n = len(panes)
        anchor = default_anchor_id or panes[-1].pane_id
        if n % 2 == 1:
            # Filling an existing column never opens a new one, so max_columns is
            # deliberately NOT checked here -- this mirrors the GUI path, where
            # `fill_singleton_column` also ignores the cap. max_columns is a
            # growth guard, not an invariant over the existing layout.
            return LayoutDecision(target_pane_id=anchor, direction="down", reason="headless_odd_down")
        current_cols = n // 2
        if max_columns and current_cols >= max_columns:
            return LayoutDecision(target_pane_id=anchor, direction="overflow",
                                  is_overflow=True, reason="max_columns_reached")
        return LayoutDecision(target_pane_id=anchor, direction="right", reason="headless_even_right")

    # Geometry-aware column grouping
    # Group panes into columns by X coordinate (fuzz threshold 2 cols)
    sorted_by_x = sorted(panes, key=lambda p: (p.x, p.y))
    columns: List[List[PaneInfo]] = []
    for p in sorted_by_x:
        matched_col = False
        for col in columns:
            if abs(col[0].x - p.x) <= 2:
                col.append(p)
                matched_col = True
                break
        if not matched_col:
            columns.append([p])

    # Sort each column's panes by Y coordinate (top to bottom)
    for col in columns:
        col.sort(key=lambda p: p.y)

    num_cols = len(columns)

    # 1. Check for any singleton column (column with only 1 pane spanning full height)
    singleton_col = None
    for col in columns:
        if len(col) == 1:
            singleton_col = col
            break

    if singleton_col is not None:
        target_p = singleton_col[0]
        # Check height
        if target_p.height > 0 and target_p.height // 2 < min_rows:
            return LayoutDecision(target_pane_id=target_p.pane_id, direction="overflow", is_overflow=True, reason="singleton_height_overflow")
        return LayoutDecision(target_pane_id=target_p.pane_id, direction="down", reason="fill_singleton_column")

    # 2. All existing columns have 2 (or more) panes -> we need to start a NEW column to the right
    if max_columns and num_cols >= max_columns:
        return LayoutDecision(target_pane_id=columns[-1][0].pane_id, direction="overflow", is_overflow=True, reason="max_columns_reached")

    # Target the top pane of the rightmost column to split right
    rightmost_top_pane = columns[-1][0]

    # Check width constraint on the rightmost column
    if rightmost_top_pane.width > 0 and rightmost_top_pane.width // 2 < min_cols:
        return LayoutDecision(target_pane_id=rightmost_top_pane.pane_id, direction="overflow", is_overflow=True, reason="column_width_overflow")

    return LayoutDecision(target_pane_id=rightmost_top_pane.pane_id, direction="right", reason="new_column_right")


def _env_int(*names: str, default: Optional[int] = None) -> Optional[int]:
    """First *valid* int among the env vars in *names*, else `default`.

    `default` is an explicit parameter rather than an `or` at the call site so a
    legitimate 0 survives (MAM_MIN_PANE_COLS=0 means 0, not the 40 default).

    An unparsable value is skipped rather than raised or treated as terminal: a
    typo in an operator's shell must not take the whole layout call down (lib.sh
    would silently fall back to 'right'), and must not shadow a later candidate
    that IS set correctly -- MAM_MIN_COLS is a legacy alias while
    MAM_MIN_PANE_COLS is the name .mam.env.example documents, so aborting on the
    first bad value would discard the documented setting. Empty values already
    fell through; this makes invalid values behave the same way.
    """
    for n in names:
        raw = os.environ.get(n, "").strip()
        if raw:
            try:
                return int(raw)
            except ValueError:
                continue
    return default


def main():
    parser = argparse.ArgumentParser(description="Compute 2xK grid TUI layout split direction")
    parser.add_argument("--min-cols", type=int, default=_env_int("MAM_MIN_COLS", "MAM_MIN_PANE_COLS", default=40))
    parser.add_argument("--min-rows", type=int, default=_env_int("MAM_MIN_ROWS", "MAM_MIN_PANE_ROWS", default=20))
    parser.add_argument("--max-cols", type=int, default=_env_int("MAM_MAX_COLS", "MAM_MAX_PANE_COLS"))
    parser.add_argument("--sample-pane", type=str, default=None)
    parser.add_argument("--json", action="store_true", help="Output full JSON decision")

    args = parser.parse_args()

    raw_input = sys.stdin.read().strip()
    data = {}
    if raw_input:
        try:
            data = json.loads(raw_input)
        except Exception:
            data = {}

    decision = compute_2xk_layout(
        data=data,
        min_cols=args.min_cols,
        min_rows=args.min_rows,
        max_columns=args.max_cols,
        default_anchor_id=args.sample_pane
    )

    if args.json:
        print(json.dumps({
            "target_pane_id": decision.target_pane_id,
            "direction": decision.direction,
            "is_overflow": decision.is_overflow,
            "reason": decision.reason
        }))
    else:
        if decision.target_pane_id:
            print(f"{decision.direction} {decision.target_pane_id}")
        else:
            print(decision.direction)


if __name__ == "__main__":
    main()