import os
import logging

log = logging.getLogger('chameleon.config')

# Define which values are read as true
TRUE = ('y', 'yes', 't', 'true', 'on', '1')

# If eager parsing is enabled, templates are parsed upon
# instantiation, rather than when first called upon; this mode is
# useful for verifying validity of templates across a project
EAGER_PARSING = os.environ.pop('CHAMELEON_EAGER', 'false')
EAGER_PARSING = EAGER_PARSING.lower() in TRUE

# Debug mode is mostly useful for debugging the template engine
# itself. When enabled, generated source code is written to disk to
# ease step-debugging and some log levels are lowered to increase
# output. Also, the generated source code is available in the
# ``source`` attribute of the template instance if compilation
# succeeded.
DEBUG_MODE = os.environ.pop('CHAMELEON_DEBUG', 'false')
DEBUG_MODE = DEBUG_MODE.lower() in TRUE

# If a cache directory is specified, template source code will be
# persisted on disk and reloaded between sessions
path = os.environ.pop('CHAMELEON_CACHE', None)
if path is not None:
    CACHE_DIRECTORY = os.path.abspath(path)
    if not os.path.exists(CACHE_DIRECTORY):
        raise ValueError(
            "Cache directory does not exist: %s." % CACHE_DIRECTORY
            )
    log.info("directory cache: %s." % CACHE_DIRECTORY)
else:
    CACHE_DIRECTORY = None

# When auto-reload is enabled, templates are reloaded on file change.
AUTO_RELOAD = os.environ.pop('CHAMELEON_RELOAD', 'false')
AUTO_RELOAD = AUTO_RELOAD.lower() in TRUE

for key in os.environ:
    if key.lower().startswith('chameleon'):
        log.warn("unknown environment variable set: \"%s\"." % key)

# This is the slice length of the expression displayed in the
# formatted exception string
SOURCE_EXPRESSION_MARKER_LENGTH = 60