#!/usr/bin/env python

import os.path
import sys

import agate
import agatesql  # noqa: F401
from pkg_resources import iter_entry_points
from sqlalchemy import create_engine, dialects

from csvkit.cli import CSVKitUtility

DIALECTS = dialects.__all__ + tuple(e.name for e in iter_entry_points('sqlalchemy.dialects'))


class CSVSQL(CSVKitUtility):
    description = 'Generate SQL statements for one or more CSV files, or execute those statements directly on a ' \
                  'database, and execute one or more SQL queries.'
    # Override 'f' because the utility accepts multiple files.
    override_flags = ['f']

    def add_arguments(self):
        self.argparser.add_argument(
            metavar='FILE', nargs='*', dest='input_paths', default=['-'],
            help='The CSV file(s) to operate on. If omitted, will accept input as piped data via STDIN.')
        self.argparser.add_argument(
            '-i', '--dialect', dest='dialect', choices=DIALECTS,
            help='Dialect of SQL to generate. Cannot be used with --db.')
        self.argparser.add_argument(
            '--db', dest='connection_string',
            help='If present, a SQLAlchemy connection string to use to directly execute generated SQL on a database.')
        self.argparser.add_argument(
            '--query',
            help='Execute one or more SQL queries delimited by ";" and output the result of the last query as CSV. '
                 'QUERY may be a filename.')
        self.argparser.add_argument(
            '--insert', dest='insert', action='store_true',
            help='Insert the data into the table. Requires --db.')
        self.argparser.add_argument(
            '--prefix', action='append', default=[],
            help='Add an expression following the INSERT keyword, like OR IGNORE or OR REPLACE.')
        self.argparser.add_argument(
            '--before-insert', dest='before_insert',
            help='Execute SQL before the INSERT command. Requires --insert.')
        self.argparser.add_argument(
            '--after-insert', dest='after_insert',
            help='Execute SQL after the INSERT command. Requires --insert.')
        self.argparser.add_argument(
            '--tables', dest='table_names',
            help='A comma-separated list of names of tables to be created. By default, the tables will be named after '
                 'the filenames without extensions or "stdin".')
        self.argparser.add_argument(
            '--no-constraints', dest='no_constraints', action='store_true',
            help='Generate a schema without length limits or null checks. Useful when sampling big tables.')
        self.argparser.add_argument(
            '--unique-constraint', dest='unique_constraint',
            help='A column-separated list of names of columns to include in a UNIQUE constraint.')
        self.argparser.add_argument(
            '--no-create', dest='no_create', action='store_true',
            help='Skip creating the table. Requires --insert.')
        self.argparser.add_argument(
            '--create-if-not-exists', dest='create_if_not_exists', action='store_true',
            help='Create the table if it does not exist, otherwise keep going. Requires --insert.')
        self.argparser.add_argument(
            '--overwrite', dest='overwrite', action='store_true',
            help='Drop the table if it already exists. Requires --insert. Cannot be used with --no-create.')
        self.argparser.add_argument(
            '--db-schema', dest='db_schema',
            help='Optional name of database schema to create table(s) in.')
        self.argparser.add_argument(
            '-y', '--snifflimit', dest='sniff_limit', type=int,
            help='Limit CSV dialect sniffing to the specified number of bytes. Specify "0" to disable sniffing.')
        self.argparser.add_argument(
            '-I', '--no-inference', dest='no_inference', action='store_true',
            help='Disable type inference when parsing the input.')
        self.argparser.add_argument(
            '--chunk-size', dest='chunk_size', type=int,
            help='Chunk size for batch insert into the table. Requires --insert.')

    def main(self):
        if sys.stdin.isatty() and not self.args.input_paths:
            self.argparser.error('You must provide an input file or piped data.')

        self.input_files = []
        self.connection = None
        self.table_names = []
        self.unique_constraint = []

        if self.args.table_names:
            self.table_names = self.args.table_names.split(',')
        if self.args.unique_constraint:
            self.unique_constraint = self.args.unique_constraint.split(',')

        # Create an SQLite database in memory if no connection string is specified
        if self.args.query and not self.args.connection_string:
            self.args.connection_string = "sqlite:///:memory:"
            self.args.insert = True

        if self.args.dialect and self.args.connection_string:
            self.argparser.error('The --dialect option is only valid when neither --db nor --query are specified.')
        if self.args.insert and not self.args.connection_string:
            self.argparser.error('The --insert option is only valid when either --db or --query is specified.')

        if self.args.no_create and not self.args.insert:
            self.argparser.error('The --no-create option is only valid if --insert is also specified.')
        if self.args.create_if_not_exists and not self.args.insert:
            self.argparser.error('The --create-if-not-exists option is only valid if --insert is also specified.')
        if self.args.overwrite and not self.args.insert:
            self.argparser.error('The --overwrite option is only valid if --insert is also specified.')
        if self.args.overwrite and self.args.no_create:
            self.argparser.error('The --overwrite option is only valid if --no-create is not specified.')
        if self.args.before_insert and not self.args.insert:
            self.argparser.error('The --before-insert option is only valid if --insert is also specified.')
        if self.args.after_insert and not self.args.insert:
            self.argparser.error('The --after-insert option is only valid if --insert is also specified.')
        if self.args.chunk_size and not self.args.insert:
            self.argparser.error('The --chunk-size option is only valid if --insert is also specified.')

        if self.args.no_create and self.args.create_if_not_exists:
            self.argparser.error('The --no-create and --create-if-not-exists options are mutually exclusive.')

        # Lazy open files
        for path in self.args.input_paths:
            self.input_files.append(self._open_input_file(path))

        # Establish database validity before reading CSV files
        if self.args.connection_string:
            try:
                engine = create_engine(self.args.connection_string)
            except ImportError as e:
                raise ImportError(
                    "You don't appear to have the necessary database backend installed for connection string you're "
                    "trying to use. Available backends include:\n\nPostgreSQL:\tpip install psycopg2\nMySQL:\t\tpip "
                    "install mysql-connector-python OR pip install mysqlclient\n\nFor details on connection strings "
                    "and other backends, please see the SQLAlchemy documentation on dialects at:\n\n"
                    "http://www.sqlalchemy.org/docs/dialects/\n\n"
                ) from e

            self.connection = engine.connect()

        try:
            self._failsafe_main()
        finally:
            for f in self.input_files:
                f.close()

            if self.connection:
                self.connection.close()

    def _failsafe_main(self):
        """
        Inner main function. If anything fails in here, file handles and
        database connections will be safely closed.
        """
        if self.connection:
            transaction = self.connection.begin()

        for f in self.input_files:
            try:
                # Try to use name specified via --tables
                table_name = self.table_names.pop(0)
            except IndexError:
                if f == sys.stdin:
                    table_name = "stdin"
                else:
                    # Use filename as table name
                    table_name = os.path.splitext(os.path.basename(f.name))[0]

            table = None

            try:
                table = agate.Table.from_csv(
                    f,
                    skip_lines=self.args.skip_lines,
                    sniff_limit=self.args.sniff_limit,
                    column_types=self.get_column_types(),
                    **self.reader_kwargs
                )
            except StopIteration:
                # Catch cases where no table data was provided and fall through
                # to query logic
                continue

            if table:
                if self.connection:
                    if self.args.before_insert:
                        for query in self.args.before_insert.split(';'):
                            self.connection.execute(query)

                    table.to_sql(
                        self.connection,
                        table_name,
                        overwrite=self.args.overwrite,
                        create=not self.args.no_create,
                        create_if_not_exists=self.args.create_if_not_exists,
                        insert=self.args.insert and len(table.rows) > 0,
                        prefixes=self.args.prefix,
                        db_schema=self.args.db_schema,
                        constraints=not self.args.no_constraints,
                        unique_constraint=self.unique_constraint,
                        chunk_size=self.args.chunk_size
                    )

                    if self.args.after_insert:
                        for query in self.args.after_insert.split(';'):
                            self.connection.execute(query)

                # Output SQL statements
                else:
                    statement = table.to_sql_create_statement(
                        table_name,
                        dialect=self.args.dialect,
                        db_schema=self.args.db_schema,
                        constraints=not self.args.no_constraints,
                        unique_constraint=self.unique_constraint
                    )

                    self.output_file.write('%s\n' % statement)

        if self.connection:
            if self.args.query:
                if os.path.exists(self.args.query):
                    with open(self.args.query, 'r') as f:
                        query = f.read()
                else:
                    query = self.args.query

                # Execute the specified SQL queries.
                queries = query.split(';')
                rows = None

                for q in queries:
                    if q.strip():
                        rows = self.connection.execute(q)

                # Output the result of the last query as CSV
                if rows.returns_rows:
                    output = agate.csv.writer(self.output_file, **self.writer_kwargs)
                    output.writerow(rows._metadata.keys)
                    for row in rows:
                        output.writerow(row)

            transaction.commit()


def launch_new_instance():
    utility = CSVSQL()
    utility.run()


if __name__ == '__main__':
    launch_new_instance()
