import os
import SocketServer
from datetime import datetime
import traceback
import django
from django.conf import settings
from django.db import connection
from django.db.backends import util
from django.template.loader import render_to_string
from django.utils import simplejson
from django.utils.encoding import force_unicode
from django.utils.hashcompat import sha_constructor
from debug_toolbar.panels import DebugPanel

# Figure out some paths
django_path = os.path.realpath(os.path.dirname(django.__file__))
socketserver_path = os.path.realpath(os.path.dirname(SocketServer.__file__))

# TODO:This should be set in the toolbar loader as a default and panels should
# get a copy of the toolbar object with access to its config dictionary
SQL_WARNING_THRESHOLD = getattr(settings, 'DEBUG_TOOLBAR_CONFIG', {}).get('SQL_WARNING_THRESHOLD', 500)

# Note: This isn't intended to catch ALL possible SQL keywords, just a good common set.
# Note: Subsets are listed last to avoid matching a subset of a keyword.  This
# whole thing could be greatly improved but for now this works.
SQL_KEYWORDS = (
    'ALTER',
    'AND',
    'ASC',
    'AS',
    'AVG',
    'COUNT',
    'CREATE',
    'DESC',
    'DELETE',
    'DISTINCT',
    'DROP',
    'FROM',
    'GROUP BY',
    'HAVING',
    'INNER JOIN',
    'INSERT',
    'IN',
    'LEFT OUTER JOIN',
    'LIKE',
    'LIMIT',
    'MAX',
    'MIN',
    'OFFSET',
    'ON',
    'ORDER BY',
    'OR',
    'SELECT',
    'SET',
    'STDDEV_POP',
    'STDDEV_SAMP',
    'SUM',
    'UPDATE',
    'VAR_POP',
    'VAR_SAMP',
    'WHERE',
)

def tidy_stacktrace(strace):
    """
    Clean up stacktrace and remove all entries that:
    1. Are part of Django (except contrib apps)
    2. Are part of SocketServer (used by Django's dev server)
    3. Are the last entry (which is part of our stacktracing code)
    """
    trace = []
    for s in strace[:-1]:
        s_path = os.path.realpath(s[0])
        if django_path in s_path and not 'django/contrib' in s_path:
            continue
        if socketserver_path in s_path:
            continue
        trace.append((s[0], s[1], s[2], s[3]))
    return trace

class DatabaseStatTracker(util.CursorDebugWrapper):
    """
    Replacement for CursorDebugWrapper which stores additional information
    in `connection.queries`.
    """
    def execute(self, sql, params=()):
        start = datetime.now()
        try:
            return self.cursor.execute(sql, params)
        finally:
            stop = datetime.now()
            duration = ms_from_timedelta(stop - start)
            stacktrace = tidy_stacktrace(traceback.extract_stack())
            _params = ''
            try:
                _params = simplejson.dumps([force_unicode(x) for x in params])
            except TypeError:
                pass # object not JSON serializable
            # We keep `sql` to maintain backwards compatibility
            self.db.queries.append({
                'sql': self.db.ops.last_executed_query(self.cursor, sql, params),
                'duration': duration,
                'raw_sql': sql,
                'params': _params,
                'hash': sha_constructor(settings.SECRET_KEY + sql + _params).hexdigest(),
                'stacktrace': stacktrace,
                'start_time': start,
                'stop_time': stop,
                'is_slow': (duration > SQL_WARNING_THRESHOLD)
            })
util.CursorDebugWrapper = DatabaseStatTracker

class SQLDebugPanel(DebugPanel):
    """
    Panel that displays information about the SQL queries run while processing
    the request.
    """
    name = 'SQL'
    has_content = True

    def __init__(self):
        self._offset = len(connection.queries)
        self._sql_time = 0
        self._queries = []

    def nav_title(self):
        return 'SQL'

    def nav_subtitle(self):
        self._queries = connection.queries[self._offset:]
        self._sql_time = sum([q['duration'] for q in self._queries])
        num_queries = len(self._queries)
        return "%d %s in %.2fms" % (
            num_queries,
            (num_queries == 1) and 'query' or 'queries',
            self._sql_time
        )

    def title(self):
        return 'SQL Queries'

    def url(self):
        return ''

    def content(self):
        width_ratio_tally = 0
        for query in self._queries:
            query['sql'] = reformat_sql(query['sql'])
            try:
                query['width_ratio'] = (query['duration'] / self._sql_time) * 100
            except ZeroDivisionError:
                query['width_ratio'] = 0
            query['start_offset'] = width_ratio_tally
            width_ratio_tally += query['width_ratio']

        context = {
            'queries': self._queries,
            'sql_time': self._sql_time,
            'is_mysql': settings.DATABASE_ENGINE == 'mysql',
        }
        return render_to_string('debug_toolbar/panels/sql.html', context)

def ms_from_timedelta(td):
    """
    Given a timedelta object, returns a float representing milliseconds
    """
    return (td.seconds * 1000) + (td.microseconds / 1000.0)

def reformat_sql(sql):
    for kwd in SQL_KEYWORDS:
        sql = sql.replace(kwd, '<strong>%s</strong>' % (kwd,))
    return sql