from __future__ import unicode_literals
import os
import re
import locale
import logging
import subprocess
import shlex
from io import open
from time import sleep

import click
import sqlparse
from configobj import ConfigObj

from . import export
from .main import special_command, NO_QUERY, PARSED_QUERY
from .favoritequeries import FavoriteQueries
from .utils import handle_cd_command
from litecli.packages.prompt_utils import confirm_destructive_query

use_expanded_output = False
PAGER_ENABLED = True
tee_file = None
once_file = once_file_args = written_to_once_file = None
favoritequeries = FavoriteQueries(ConfigObj())


@export
def set_favorite_queries(config):
    global favoritequeries
    favoritequeries = FavoriteQueries(config)


@export
def set_pager_enabled(val):
    global PAGER_ENABLED
    PAGER_ENABLED = val


@export
def is_pager_enabled():
    return PAGER_ENABLED


@export
@special_command(
    "pager",
    "\\P [command]",
    "Set PAGER. Print the query results via PAGER.",
    arg_type=PARSED_QUERY,
    aliases=("\\P",),
    case_sensitive=True,
)
def set_pager(arg, **_):
    if arg:
        os.environ["PAGER"] = arg
        msg = "PAGER set to %s." % arg
        set_pager_enabled(True)
    else:
        if "PAGER" in os.environ:
            msg = "PAGER set to %s." % os.environ["PAGER"]
        else:
            # This uses click's default per echo_via_pager.
            msg = "Pager enabled."
        set_pager_enabled(True)

    return [(None, None, None, msg)]


@export
@special_command(
    "nopager",
    "\\n",
    "Disable pager, print to stdout.",
    arg_type=NO_QUERY,
    aliases=("\\n",),
    case_sensitive=True,
)
def disable_pager():
    set_pager_enabled(False)
    return [(None, None, None, "Pager disabled.")]


@export
def set_expanded_output(val):
    global use_expanded_output
    use_expanded_output = val


@export
def is_expanded_output():
    return use_expanded_output


_logger = logging.getLogger(__name__)


@export
def editor_command(command):
    """
    Is this an external editor command?
    :param command: string
    """
    # It is possible to have `\e filename` or `SELECT * FROM \e`. So we check
    # for both conditions.
    return command.strip().endswith("\\e") or command.strip().startswith("\\e")


@export
def get_filename(sql):
    if sql.strip().startswith("\\e"):
        command, _, filename = sql.partition(" ")
        return filename.strip() or None


@export
def get_editor_query(sql):
    """Get the query part of an editor command."""
    sql = sql.strip()

    # The reason we can't simply do .strip('\e') is that it strips characters,
    # not a substring. So it'll strip "e" in the end of the sql also!
    # Ex: "select * from style\e" -> "select * from styl".
    pattern = re.compile(r"(^\\e|\\e$)")
    while pattern.search(sql):
        sql = pattern.sub("", sql)

    return sql


@export
def open_external_editor(filename=None, sql=None):
    """Open external editor, wait for the user to type in their query, return
    the query.

    :return: list with one tuple, query as first element.

    """

    message = None
    filename = filename.strip().split(" ", 1)[0] if filename else None

    sql = sql or ""
    MARKER = "# Type your query above this line.\n"

    # Populate the editor buffer with the partial sql (if available) and a
    # placeholder comment.
    query = click.edit(
        "{sql}\n\n{marker}".format(sql=sql, marker=MARKER),
        filename=filename,
        extension=".sql",
    )

    if filename:
        try:
            with open(filename, encoding="utf-8") as f:
                query = f.read()
        except IOError:
            message = "Error reading file: %s." % filename

    if query is not None:
        query = query.split(MARKER, 1)[0].rstrip("\n")
    else:
        # Don't return None for the caller to deal with.
        # Empty string is ok.
        query = sql

    return (query, message)


@special_command(
    "\\f",
    "\\f [name [args..]]",
    "List or execute favorite queries.",
    arg_type=PARSED_QUERY,
    case_sensitive=True,
)
def execute_favorite_query(cur, arg, verbose=False, **_):
    """Returns (title, rows, headers, status)"""
    if arg == "":
        for result in list_favorite_queries():
            yield result

    """Parse out favorite name and optional substitution parameters"""
    name, _, arg_str = arg.partition(" ")
    args = shlex.split(arg_str)

    query = favoritequeries.get(name)
    if query is None:
        message = "No favorite query: %s" % (name)
        yield (None, None, None, message)
    elif "?" in query:
        for sql in sqlparse.split(query):
            sql = sql.rstrip(";")
            title = "> %s" % (sql) if verbose else None
            cur.execute(sql, args)
            if cur.description:
                headers = [x[0] for x in cur.description]
                yield (title, cur, headers, None)
            else:
                yield (title, None, None, None)
    else:
        query, arg_error = subst_favorite_query_args(query, args)
        if arg_error:
            yield (None, None, None, arg_error)
        else:
            for sql in sqlparse.split(query):
                sql = sql.rstrip(";")
                title = "> %s" % (sql) if verbose else None
                cur.execute(sql)
                if cur.description:
                    headers = [x[0] for x in cur.description]
                    yield (title, cur, headers, None)
                else:
                    yield (title, None, None, None)


def list_favorite_queries():
    """List of all favorite queries.
    Returns (title, rows, headers, status)"""

    headers = ["Name", "Query"]
    rows = [(r, favoritequeries.get(r)) for r in favoritequeries.list()]

    if not rows:
        status = "\nNo favorite queries found." + favoritequeries.usage
    else:
        status = ""
    return [("", rows, headers, status)]


def subst_favorite_query_args(query, args):
    """replace positional parameters ($1...$N) in query."""
    for idx, val in enumerate(args):
        shell_subst_var = "$" + str(idx + 1)
        question_subst_var = "?"
        if shell_subst_var in query:
            query = query.replace(shell_subst_var, val)
        elif question_subst_var in query:
            query = query.replace(question_subst_var, val, 1)
        else:
            return [
                None,
                "Too many arguments.\nQuery does not have enough place holders to substitute.\n" + query,
            ]

    match = re.search(r"\?|\$\d+", query)
    if match:
        return [
            None,
            "missing substitution for " + match.group(0) + " in query:\n  " + query,
        ]

    return [query, None]


@special_command("\\fs", "\\fs name query", "Save a favorite query.")
def save_favorite_query(arg, **_):
    """Save a new favorite query.
    Returns (title, rows, headers, status)"""

    usage = "Syntax: \\fs name query.\n\n" + favoritequeries.usage
    if not arg:
        return [(None, None, None, usage)]

    name, _, query = arg.partition(" ")

    # If either name or query is missing then print the usage and complain.
    if (not name) or (not query):
        return [(None, None, None, usage + "Err: Both name and query are required.")]

    favoritequeries.save(name, query)
    return [(None, None, None, "Saved.")]


@special_command("\\fd", "\\fd [name]", "Delete a favorite query.")
def delete_favorite_query(arg, **_):
    """Delete an existing favorite query."""
    usage = "Syntax: \\fd name.\n\n" + favoritequeries.usage
    if not arg:
        return [(None, None, None, usage)]

    status = favoritequeries.delete(arg)

    return [(None, None, None, status)]


@special_command("system", "system [command]", "Execute a system shell command.")
def execute_system_command(arg, **_):
    """Execute a system shell command."""
    usage = "Syntax: system [command].\n"

    if not arg:
        return [(None, None, None, usage)]

    try:
        command = arg.strip()
        if command.startswith("cd"):
            ok, error_message = handle_cd_command(arg)
            if not ok:
                return [(None, None, None, error_message)]
            return [(None, None, None, "")]

        args = arg.split(" ")
        process = subprocess.Popen(args, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
        output, error = process.communicate()
        response = output if not error else error

        # Python 3 returns bytes. This needs to be decoded to a string.
        if isinstance(response, bytes):
            encoding = locale.getpreferredencoding(False)
            response = response.decode(encoding)

        return [(None, None, None, response)]
    except OSError as e:
        return [(None, None, None, "OSError: %s" % e.strerror)]


def parseargfile(arg):
    if arg.startswith("-o "):
        mode = "w"
        filename = arg[3:]
    else:
        mode = "a"
        filename = arg

    if not filename:
        raise TypeError("You must provide a filename.")

    return {"file": os.path.expanduser(filename), "mode": mode}


@special_command(
    "tee",
    "tee [-o] filename",
    "Append all results to an output file (overwrite using -o).",
)
def set_tee(arg, **_):
    global tee_file

    try:
        tee_file = open(**parseargfile(arg))
    except (IOError, OSError) as e:
        raise OSError("Cannot write to file '{}': {}".format(e.filename, e.strerror))

    return [(None, None, None, "")]


@export
def close_tee():
    global tee_file
    if tee_file:
        tee_file.close()
        tee_file = None


@special_command("notee", "notee", "Stop writing results to an output file.")
def no_tee(arg, **_):
    close_tee()
    return [(None, None, None, "")]


@export
def write_tee(output):
    global tee_file
    if tee_file:
        click.echo(output, file=tee_file, nl=False)
        click.echo("\n", file=tee_file, nl=False)
        tee_file.flush()


@special_command(
    ".once",
    "\\o [-o] filename",
    "Append next result to an output file (overwrite using -o).",
    aliases=("\\o", "\\once"),
)
def set_once(arg, **_):
    global once_file_args

    once_file_args = parseargfile(arg)

    return [(None, None, None, "")]


@export
def write_once(output):
    global once_file, written_to_once_file
    if output and once_file_args:
        if once_file is None:
            try:
                once_file = open(**once_file_args)
            except (IOError, OSError) as e:
                once_file = None
                raise OSError("Cannot write to file '{}': {}".format(e.filename, e.strerror))

        click.echo(output, file=once_file, nl=False)
        click.echo("\n", file=once_file, nl=False)
        written_to_once_file = True


@export
def unset_once_if_written():
    """Unset the once file, if it has been written to."""
    global once_file, once_file_args, written_to_once_file
    if once_file and written_to_once_file:
        once_file.close()
        once_file = once_file_args = written_to_once_file = None


@special_command(
    "watch",
    "watch [seconds] [-c] query",
    "Executes the query every [seconds] seconds (by default 5).",
)
def watch_query(arg, **kwargs):
    usage = """Syntax: watch [seconds] [-c] query.
    * seconds: The interval at the query will be repeated, in seconds.
               By default 5.
    * -c: Clears the screen between every iteration.
"""
    if not arg:
        yield (None, None, None, usage)
        raise StopIteration
    seconds = 5
    clear_screen = False
    statement = None
    while statement is None:
        arg = arg.strip()
        if not arg:
            # Oops, we parsed all the arguments without finding a statement
            yield (None, None, None, usage)
            raise StopIteration
        (current_arg, _, arg) = arg.partition(" ")
        try:
            seconds = float(current_arg)
            continue
        except ValueError:
            pass
        if current_arg == "-c":
            clear_screen = True
            continue
        statement = "{0!s} {1!s}".format(current_arg, arg)
    destructive_prompt = confirm_destructive_query(statement)
    if destructive_prompt is False:
        click.secho("Wise choice!")
        raise StopIteration
    elif destructive_prompt is True:
        click.secho("Your call!")
    cur = kwargs["cur"]
    sql_list = [(sql.rstrip(";"), "> {0!s}".format(sql)) for sql in sqlparse.split(statement)]
    old_pager_enabled = is_pager_enabled()
    while True:
        if clear_screen:
            click.clear()
        try:
            # Somewhere in the code the pager its activated after every yield,
            # so we disable it in every iteration
            set_pager_enabled(False)
            for sql, title in sql_list:
                cur.execute(sql)
                if cur.description:
                    headers = [x[0] for x in cur.description]
                    yield (title, cur, headers, None)
                else:
                    yield (title, None, None, None)
            sleep(seconds)
        except KeyboardInterrupt:
            # This prints the Ctrl-C character in its own line, which prevents
            # to print a line with the cursor positioned behind the prompt
            click.secho("", nl=True)
            raise StopIteration
        finally:
            set_pager_enabled(old_pager_enabled)
