import json
import numbers

from .utils import (
    detect_json1,
    escape_sqlite,
)


class Filter:
    key = None
    display = None
    no_argument = False

    def where_clause(self, table, column, value, param_counter):
        raise NotImplementedError

    def human_clause(self, column, value):
        raise NotImplementedError


class TemplatedFilter(Filter):
    def __init__(self, key, display, sql_template, human_template, format='{}', numeric=False, no_argument=False):
        self.key = key
        self.display = display
        self.sql_template = sql_template
        self.human_template = human_template
        self.format = format
        self.numeric = numeric
        self.no_argument = no_argument

    def where_clause(self, table, column, value, param_counter):
        converted = self.format.format(value)
        if self.numeric and converted.isdigit():
            converted = int(converted)
        if self.no_argument:
            kwargs = {
                'c': column,
            }
            converted = None
        else:
            kwargs = {
                'c': column,
                'p': 'p{}'.format(param_counter),
                't': table,
            }
        return self.sql_template.format(**kwargs), converted

    def human_clause(self, column, value):
        if callable(self.human_template):
            template = self.human_template(column, value)
        else:
            template = self.human_template
        if self.no_argument:
            return template.format(c=column)
        else:
            return template.format(c=column, v=value)


class InFilter(Filter):
    key = 'in'
    display = 'in'

    def __init__(self):
        pass

    def split_value(self, value):
        if value.startswith("["):
            return json.loads(value)
        else:
            return [v.strip() for v in value.split(",")]

    def where_clause(self, table, column, value, param_counter):
        values = self.split_value(value)
        params = [":p{}".format(param_counter + i) for i in range(len(values))]
        sql = "{} in ({})".format(escape_sqlite(column), ", ".join(params))
        return sql, values

    def human_clause(self, column, value):
        return "{} in {}".format(column, json.dumps(self.split_value(value)))


class Filters:
    _filters = [
        # key, display, sql_template, human_template, format=, numeric=, no_argument=
        TemplatedFilter('exact', '=', '"{c}" = :{p}', lambda c, v: '{c} = {v}' if v.isdigit() else '{c} = "{v}"'),
        TemplatedFilter('not', '!=', '"{c}" != :{p}', lambda c, v: '{c} != {v}' if v.isdigit() else '{c} != "{v}"'),
        TemplatedFilter('contains', 'contains', '"{c}" like :{p}', '{c} contains "{v}"', format='%{}%'),
        TemplatedFilter('endswith', 'ends with', '"{c}" like :{p}', '{c} ends with "{v}"', format='%{}'),
        TemplatedFilter('startswith', 'starts with', '"{c}" like :{p}', '{c} starts with "{v}"', format='{}%'),
        TemplatedFilter('gt', '>', '"{c}" > :{p}', '{c} > {v}', numeric=True),
        TemplatedFilter('gte', '\u2265', '"{c}" >= :{p}', '{c} \u2265 {v}', numeric=True),
        TemplatedFilter('lt', '<', '"{c}" < :{p}', '{c} < {v}', numeric=True),
        TemplatedFilter('lte', '\u2264', '"{c}" <= :{p}', '{c} \u2264 {v}', numeric=True),
        TemplatedFilter('like', 'like', '"{c}" like :{p}', '{c} like "{v}"'),
        TemplatedFilter('glob', 'glob', '"{c}" glob :{p}', '{c} glob "{v}"'),
        InFilter(),
    ] + ([TemplatedFilter('arraycontains', 'array contains', """rowid in (
            select {t}.rowid from {t}, json_each({t}.{c}) j
            where j.value = :{p}
        )""", '{c} contains "{v}"')
    ] if detect_json1() else []) + [
        TemplatedFilter('isnull', 'is null', '"{c}" is null', '{c} is null', no_argument=True),
        TemplatedFilter('notnull', 'is not null', '"{c}" is not null', '{c} is not null', no_argument=True),
        TemplatedFilter('isblank', 'is blank', '("{c}" is null or "{c}" = "")', '{c} is blank', no_argument=True),
        TemplatedFilter('notblank', 'is not blank', '("{c}" is not null and "{c}" != "")', '{c} is not blank', no_argument=True),
    ]
    _filters_by_key = {
        f.key: f for f in _filters
    }

    def __init__(self, pairs, units={}, ureg=None):
        self.pairs = pairs
        self.units = units
        self.ureg = ureg

    def lookups(self):
        "Yields (lookup, display, no_argument) pairs"
        for filter in self._filters:
            yield filter.key, filter.display, filter.no_argument

    def human_description_en(self, extra=None):
        bits = []
        if extra:
            bits.extend(extra)
        for column, lookup, value in self.selections():
            filter = self._filters_by_key.get(lookup, None)
            if filter:
                bits.append(filter.human_clause(column, value))
        # Comma separated, with an ' and ' at the end
        and_bits = []
        commas, tail = bits[:-1], bits[-1:]
        if commas:
            and_bits.append(', '.join(commas))
        if tail:
            and_bits.append(tail[0])
        s = ' and '.join(and_bits)
        if not s:
            return ''
        return 'where {}'.format(s)

    def selections(self):
        "Yields (column, lookup, value) tuples"
        for key, value in self.pairs:
            if '__' in key:
                column, lookup = key.rsplit('__', 1)
            else:
                column = key
                lookup = 'exact'
            yield column, lookup, value

    def has_selections(self):
        return bool(self.pairs)

    def convert_unit(self, column, value):
        "If the user has provided a unit in the query, convert it into the column unit, if present."
        if column not in self.units:
            return value

        # Try to interpret the value as a unit
        value = self.ureg(value)
        if isinstance(value, numbers.Number):
            # It's just a bare number, assume it's the column unit
            return value

        column_unit = self.ureg(self.units[column])
        return value.to(column_unit).magnitude

    def build_where_clauses(self, table):
        sql_bits = []
        params = {}
        i = 0
        for column, lookup, value in self.selections():
            filter = self._filters_by_key.get(lookup, None)
            if filter:
                sql_bit, param = filter.where_clause(table, column, self.convert_unit(column, value), i)
                sql_bits.append(sql_bit)
                if param is not None:
                    if not isinstance(param, list):
                        param = [param]
                    for individual_param in param:
                        param_id = 'p{}'.format(i)
                        params[param_id] = individual_param
                        i += 1
        return sql_bits, params