from __future__ import annotations

from typing import Dict, Tuple

from .models import Coord, Puzzle, GameState, Word


def _chebyshev_distance(a: Coord, b: Coord) -> int:
    """8-neighborhood distance (max norm)."""
    return max(abs(a.x - b.x), abs(a.y - b.y))


def build_letter_map(puzzle: Puzzle, skip_validation: bool = True) -> Dict[Coord, str]:
    """Build a coordinate->letter map for the given puzzle.

    Spacer support (0–2):
    - spacer = 0: words may touch (no separation enforced).
    - spacer = 1: words must be separated by at least 1 blank tile
      (no two letters from different words at Chebyshev distance <= 1).
    - spacer = 2: at least 2 blank tiles between words
      (no two letters from different words at Chebyshev distance <= 2).

    Overlaps are not handled here (negative spacer not supported in this function).
    This function raises ValueError if the configured spacing is violated.

    Args:
        puzzle: The puzzle to build the letter map for
        skip_validation: If True, skip spacer validation (default: True).
                        Validation is expensive and only needed during puzzle
                        generation, not during gameplay.
    """
    mapping: Dict[Coord, str] = {}

    spacer = getattr(puzzle, "spacer", 1)

    # Build mapping normally (no overlap merging beyond first-come-wins semantics)
    for w in puzzle.words:
        for idx, c in enumerate(w.cells):
            ch = w.text[idx]
            if c not in mapping:
                mapping[c] = ch
            else:
                # If an explicit overlap occurs, we don't support it here.
                # Keep the first-seen letter and continue.
                pass

    # Enforce spacer in the range 0–2 (only when validation is requested)
    if not skip_validation and spacer in (1, 2):
        # Prepare sets of cells per word
        word_cells = [set(w.cells) for w in puzzle.words]
        for i in range(len(word_cells)):
            for j in range(i + 1, len(word_cells)):
                cells_i = word_cells[i]
                cells_j = word_cells[j]
                # If any pair is too close, it's a violation
                for c1 in cells_i:
                    # Early exit by scanning a small neighborhood around c1
                    # since Chebyshev distance <= spacer
                    for c2 in cells_j:
                        if _chebyshev_distance(c1, c2) <= spacer:
                            raise ValueError(
                                f"Words too close (spacer={spacer}): {c1} and {c2}"
                            )

    # spacer == 0 -> no checks; other values are ignored here intentionally

    return mapping


def reveal_cell(state: GameState, letter_map: Dict[Coord, str], coord: Coord) -> None:
    if coord in state.revealed:
        state.last_action = "Already revealed."
        return
    state.revealed.add(coord)
    # Determine if this reveal uncovered a letter or an empty cell
    ch = letter_map.get(coord, "·")
    # Only allow guessing if a letter was revealed; preserve existing True (e.g., after a correct guess)
    state.can_guess = state.can_guess or (ch != "·")
    if ch == "·":
        state.last_action = f"Revealed empty at ({coord.x+1},{coord.y+1})."
    else:
        state.last_action = f"Revealed '{ch}' at ({coord.x+1},{coord.y+1})."


def guess_word(state: GameState, guess_text: str) -> Tuple[bool, int]:
    if not state.can_guess:
        state.last_action = "You must reveal a cell before guessing."
        return False, 0
    guess = (guess_text or "").strip().upper()
    if not (len(guess) in (4, 5, 6) and guess.isalpha()):
        state.last_action = "Guess must be A–Z and length 4, 5, or 6."
        state.can_guess = False
        return False, 0
    if guess in state.guessed:
        state.last_action = f"Already guessed {guess}."
        state.can_guess = False
        return False, 0

    # Find matching unguessed word
    target: Word | None = None
    for w in state.puzzle.words:
        if w.text == guess and w.text not in state.guessed:
            target = w
            break

    if target is None:
        state.last_action = f"Try Again! '{guess}' is not in the puzzle."
        state.can_guess = False
        return False, 0

    # Scoring: base = length, bonus = unrevealed cells in that word
    unrevealed = sum(1 for c in target.cells if c not in state.revealed)
    points = target.length + unrevealed
    state.score += points
    state.points_by_word[target.text] = points

    # Reveal all cells of the word
    for c in target.cells:
        state.revealed.add(c)
    state.guessed.add(target.text)

    state.last_action = f"Correct! +{points} points for {target.text}."
    if state.game_mode == "classic":
        state.can_guess = True  # <-- Allow another guess after a correct guess
    else:
        state.can_guess = False
    return True, points


def is_game_over(state: GameState) -> bool:
    # Game ends if all words are guessed
    if len(state.guessed) == 6:
        return True
    # Game ends if all word cells are revealed
    # Use pre-computed _all_word_cells set from puzzle for performance
    if state.puzzle._all_word_cells.issubset(state.revealed):
        return True
    return False


def compute_tier(score: int) -> str:
    if score >= 42:
        return "Fantastic"
    if 38 <= score <= 41:
        return "Great"
    if 34 <= score <= 37:
        return "Good"
    return "Keep practicing"

def hidden_word_display(letters_display: int, character: str = "?") -> str:
    """Return a string of characters of length letters_display."""
    return character * letters_display

def auto_mark_completed_words(state: GameState) -> bool:
    """Automatically mark words as found when all their letters are revealed.

    Returns True if any word state changed (e.g., guessed/score/points).
    Scoring in this case is base length only (no unrevealed bonus).
    """
    changed = False
    for w in state.puzzle.words:
        if w.text in state.guessed:
            continue
        if all(c in state.revealed for c in w.cells):
            # Award base points if not already assigned
            if w.text not in state.points_by_word:
                base_points = w.length
                state.points_by_word[w.text] = base_points
                state.score += base_points
            state.guessed.add(w.text)
            changed = True
    if changed:
        # Do not alter can_guess; just note the auto-complete
        state.last_action = (state.last_action or "") + "\nAuto-complete: revealed word(s) marked as found."
    return changed