import os
import typing as t
from warnings import warn

from .app import Flask
from .blueprints import Blueprint
from .globals import _request_ctx_stack


class UnexpectedUnicodeError(AssertionError, UnicodeError):
    """Raised in places where we want some better error reporting for
    unexpected unicode or binary data.
    """


class DebugFilesKeyError(KeyError, AssertionError):
    """Raised from request.files during debugging.  The idea is that it can
    provide a better error message than just a generic KeyError/BadRequest.
    """

    def __init__(self, request, key):
        form_matches = request.form.getlist(key)
        buf = [
            f"You tried to access the file {key!r} in the request.files"
            " dictionary but it does not exist. The mimetype for the"
            f" request is {request.mimetype!r} instead of"
            " 'multipart/form-data' which means that no file contents"
            " were transmitted. To fix this error you should provide"
            ' enctype="multipart/form-data" in your form.'
        ]
        if form_matches:
            names = ", ".join(repr(x) for x in form_matches)
            buf.append(
                "\n\nThe browser instead transmitted some file names. "
                f"This was submitted: {names}"
            )
        self.msg = "".join(buf)

    def __str__(self):
        return self.msg


class FormDataRoutingRedirect(AssertionError):
    """This exception is raised by Flask in debug mode if it detects a
    redirect caused by the routing system when the request method is not
    GET, HEAD or OPTIONS.  Reasoning: form data will be dropped.
    """

    def __init__(self, request):
        exc = request.routing_exception
        buf = [
            f"A request was sent to this URL ({request.url}) but a"
            " redirect was issued automatically by the routing system"
            f" to {exc.new_url!r}."
        ]

        # In case just a slash was appended we can be extra helpful
        if f"{request.base_url}/" == exc.new_url.split("?")[0]:
            buf.append(
                "  The URL was defined with a trailing slash so Flask"
                " will automatically redirect to the URL with the"
                " trailing slash if it was accessed without one."
            )

        buf.append(
            "  Make sure to directly send your"
            f" {request.method}-request to this URL since we can't make"
            " browsers or HTTP clients redirect with form data reliably"
            " or without user interaction."
        )
        buf.append("\n\nNote: this exception is only raised in debug mode")
        AssertionError.__init__(self, "".join(buf).encode("utf-8"))


def attach_enctype_error_multidict(request):
    """Since Flask 0.8 we're monkeypatching the files object in case a
    request is detected that does not use multipart form data but the files
    object is accessed.
    """
    oldcls = request.files.__class__

    class newcls(oldcls):
        def __getitem__(self, key):
            try:
                return oldcls.__getitem__(self, key)
            except KeyError as e:
                if key not in request.form:
                    raise

                raise DebugFilesKeyError(request, key) from e

    newcls.__name__ = oldcls.__name__
    newcls.__module__ = oldcls.__module__
    request.files.__class__ = newcls


def _dump_loader_info(loader) -> t.Generator:
    yield f"class: {type(loader).__module__}.{type(loader).__name__}"
    for key, value in sorted(loader.__dict__.items()):
        if key.startswith("_"):
            continue
        if isinstance(value, (tuple, list)):
            if not all(isinstance(x, str) for x in value):
                continue
            yield f"{key}:"
            for item in value:
                yield f"  - {item}"
            continue
        elif not isinstance(value, (str, int, float, bool)):
            continue
        yield f"{key}: {value!r}"


def explain_template_loading_attempts(app: Flask, template, attempts) -> None:
    """This should help developers understand what failed"""
    info = [f"Locating template {template!r}:"]
    total_found = 0
    blueprint = None
    reqctx = _request_ctx_stack.top
    if reqctx is not None and reqctx.request.blueprint is not None:
        blueprint = reqctx.request.blueprint

    for idx, (loader, srcobj, triple) in enumerate(attempts):
        if isinstance(srcobj, Flask):
            src_info = f"application {srcobj.import_name!r}"
        elif isinstance(srcobj, Blueprint):
            src_info = f"blueprint {srcobj.name!r} ({srcobj.import_name})"
        else:
            src_info = repr(srcobj)

        info.append(f"{idx + 1:5}: trying loader of {src_info}")

        for line in _dump_loader_info(loader):
            info.append(f"       {line}")

        if triple is None:
            detail = "no match"
        else:
            detail = f"found ({triple[1] or '<string>'!r})"
            total_found += 1
        info.append(f"       -> {detail}")

    seems_fishy = False
    if total_found == 0:
        info.append("Error: the template could not be found.")
        seems_fishy = True
    elif total_found > 1:
        info.append("Warning: multiple loaders returned a match for the template.")
        seems_fishy = True

    if blueprint is not None and seems_fishy:
        info.append(
            "  The template was looked up from an endpoint that belongs"
            f" to the blueprint {blueprint!r}."
        )
        info.append("  Maybe you did not place a template in the right folder?")
        info.append("  See https://flask.palletsprojects.com/blueprints/#templates")

    app.logger.info("\n".join(info))


def explain_ignored_app_run() -> None:
    if os.environ.get("WERKZEUG_RUN_MAIN") != "true":
        warn(
            Warning(
                "Silently ignoring app.run() because the application is"
                " run from the flask command line executable. Consider"
                ' putting app.run() behind an if __name__ == "__main__"'
                " guard to silence this warning."
            ),
            stacklevel=3,
        )