"""
Logic functions for Sudoku
"""


# Disable 'invalid-name', b/c 'logic' package uses unconventional names
# pylint: disable=C0103


from pyeda.boolalg.bfarray import exprvars
from pyeda.boolalg.expr import And, OneHot, expr2dimacscnf

DIGITS = "123456789"


class SudokuSolver:
    """Logical constraints for 3x3 Sudoku"""
    def __init__(self):
        self.X = exprvars("x", (1, 10), (1, 10), (1, 10))

        V = And(*[And(*[OneHot(*[self.X[r, c, v] for v in range(1, 10)])
                        for c in range(1, 10)])
                  for r in range(1, 10)])
        R = And(*[And(*[OneHot(*[self.X[r, c, v] for c in range(1, 10)])
                        for v in range(1, 10)])
                  for r in range(1, 10)])
        C = And(*[And(*[OneHot(*[self.X[r, c, v] for r in range(1, 10)])
                        for v in range(1, 10)])
                  for c in range(1, 10)])
        B = And(*[And(*[OneHot(*[self.X[3*br+r, 3*bc+c, v]
                                 for r in range(1, 4)
                                 for c in range(1, 4)])
                        for v in range(1, 10)])
                  for br in range(3) for bc in range(3)])

        self.litmap, self.S = expr2dimacscnf(And(V, R, C, B))

    def solve(self, grid):
        """Return a solution point for a Sudoku grid."""
        soln = self.S.satisfy_one(assumptions=self._parse_grid(grid))
        return self.S.soln2point(soln, self.litmap)

    def display_solve(self, grid):
        """Return a solution point for a Sudoku grid as a string."""
        return self._soln2str(self.solve(grid))

    def _parse_grid(self, grid):
        """Return the input constraints for a Sudoku grid."""
        chars = [c for c in grid if c in DIGITS or c in "0."]
        if len(chars) != 9**2:
            raise ValueError("expected 9x9 grid")
        return [self.litmap[self.X[i // 9 + 1, i % 9 + 1, int(c)]]
                for i, c in enumerate(chars) if c in DIGITS]

    def _soln2str(self, soln, fancy=False):
        """Convert a Sudoku solution point to a string."""
        chars = []
        for r in range(1, 10):
            for c in range(1, 10):
                if fancy and c in (4, 7):
                    chars.append("|")
                chars.append(self._get_val(soln, r, c))
            if fancy and r != 9:
                chars.append("\n")
                if r in (3, 6):
                    chars.append("---+---+---\n")
        return "".join(chars)

    def _get_val(self, soln, r, c):
        """Return the string value for a solution coordinate."""
        for v in range(1, 10):
            if soln[self.X[r, c, v]]:
                return DIGITS[v-1]
        return "X"
