"""Process URI templates per http://tools.ietf.org/html/rfc6570."""

import collections
import re
from typing import Dict, Iterable, List

from .expansions import (CommaExpansion, Expansion,
                         FormStyleQueryContinuation, FormStyleQueryExpansion,
                         FragmentExpansion, LabelExpansion, Literal,
                         PathExpansion, PathStyleExpansion,
                         ReservedCommaExpansion, ReservedExpansion, SimpleExpansion)
from .variable import Variable


class ExpansionReservedError(Exception):
    """Exception thrown for reserved but unsupported expansions."""

    expansion: str

    def __init__(self, expansion: str) -> None:
        self.expansion = expansion

    def __str__(self) -> str:
        """Convert to string."""
        return 'Unsupported expansion: ' + self.expansion


class ExpansionInvalidError(Exception):
    """Exception thrown for unknown expansions."""

    expansion: str

    def __init__(self, expansion: str) -> None:
        self.expansion = expansion

    def __str__(self) -> str:
        """Convert to string."""
        return 'Bad expansion: ' + self.expansion


class URITemplate(object):
    """
    URI Template object.

    Constructor may raise ExpansionReservedError, ExpansionInvalidError, or VariableInvalidError.
    """

    expansions: List[Expansion]

    def __init__(self, template: str) -> None:
        self.expansions = []
        parts = re.split(r'(\{[^\}]*\})', template)
        for part in parts:
            if (part):
                if (('{' == part[0]) and ('}' == part[-1])):
                    expansion = part[1:-1]
                    if (re.match('^([a-zA-Z0-9_]|%[0-9a-fA-F][0-9a-fA-F]).*$', expansion)):
                        self.expansions.append(SimpleExpansion(expansion))
                    elif ('+' == part[1]):
                        self.expansions.append(ReservedExpansion(expansion))
                    elif ('#' == part[1]):
                        self.expansions.append(FragmentExpansion(expansion))
                    elif ('.' == part[1]):
                        self.expansions.append(LabelExpansion(expansion))
                    elif ('/' == part[1]):
                        self.expansions.append(PathExpansion(expansion))
                    elif (';' == part[1]):
                        self.expansions.append(PathStyleExpansion(expansion))
                    elif ('?' == part[1]):
                        self.expansions.append(FormStyleQueryExpansion(expansion))
                    elif ('&' == part[1]):
                        self.expansions.append(FormStyleQueryContinuation(expansion))
                    elif (',' == part[1]):
                        if ((1 < len(part)) and ('+' == part[2])):
                            self.expansions.append(ReservedCommaExpansion(expansion))
                        else:
                            self.expansions.append(CommaExpansion(expansion))
                    elif (part[1] in '=!@|'):
                        raise ExpansionReservedError(part)
                    else:
                        raise ExpansionInvalidError(part)
                else:
                    if (('{' not in part) and ('}' not in part)):
                        self.expansions.append(Literal(part))
                    else:
                        raise ExpansionInvalidError(part)

    @property
    def variables(self) -> Iterable[Variable]:
        """Get all variables in template."""
        vars: Dict[str, Variable] = collections.OrderedDict()
        for expansion in self.expansions:
            for var in expansion.variables:
                vars[var.name] = var
        return vars.values()

    @property
    def variable_names(self) -> Iterable[str]:
        """Get names of all variables in template."""
        vars: Dict[str, Variable] = collections.OrderedDict()
        for expansion in self.expansions:
            for var in expansion.variables:
                vars[var.name] = var
        return [var.name for var in vars.values()]

    def expand(self, **kwargs) -> str:
        """
        Expand the template.

        May raise ExpansionFailed if a composite value is passed to a variable with a prefix modifier.
        """
        expanded = [expansion.expand(kwargs) for expansion in self.expansions]
        return ''.join([expansion for expansion in expanded if (expansion is not None)])

    def partial(self, **kwargs) -> 'URITemplate':
        """
        Expand the template, preserving expansions for missing variables.

        May raise ExpansionFailed if a composite value is passed to a variable with a prefix modifier.
        """
        expanded = [expansion.partial(kwargs) for expansion in self.expansions]
        return URITemplate(''.join(expanded))

    @property
    def expanded(self) -> bool:
        """Determine if template is fully expanded."""
        return (str(self) == self.expand())

    def __str__(self) -> str:
        """Convert to string, returns original template."""
        return ''.join([str(expansion) for expansion in self.expansions])

    def __repr__(self) -> str:
        """Convert to string, returns original template."""
        return str(self)
