"""Mailcap file handling. See RFC 1524."""

import os
import warnings

__all__ = ["getcaps","findmatch"]


def lineno_sort_key(entry):
 # Sort in ascending order, with unspecified entries at the end
 if 'lineno' in entry:
 return 0, entry['lineno']
 else:
 return 1, 0


# Part 1: top-level interface.

def getcaps():
 """Return a dictionary containing the mailcap database.

 The dictionary maps a MIME type (in all lowercase, e.g. 'text/plain')
 to a list of dictionaries corresponding to mailcap entries. The list
 collects all the entries for that MIME type from all available mailcap
 files. Each dictionary contains key-value pairs for that MIME type,
 where the viewing command is stored with the key "view".

 """
 caps = {}
 lineno = 0
 for mailcap in listmailcapfiles():
 try:
 fp = open(mailcap, 'r')
 except OSError:
 continue
 with fp:
 morecaps, lineno = _readmailcapfile(fp, lineno)
 for key, value in morecaps.items():
 if not key in caps:
 caps[key] = value
 else:
 caps[key] = caps[key] + value
 return caps

def listmailcapfiles():
 """Return a list of all mailcap files found on the system."""
 # This is mostly a Unix thing, but we use the OS path separator anyway
 if 'MAILCAPS' in os.environ:
 pathstr = os.environ['MAILCAPS']
 mailcaps = pathstr.split(os.pathsep)
 else:
 if 'HOME' in os.environ:
 home = os.environ['HOME']
 else:
 # Don't bother with getpwuid()
 home = '.' # Last resort
 mailcaps = [home + '/.mailcap', '/etc/mailcap',
 '/usr/etc/mailcap', '/usr/local/etc/mailcap']
 return mailcaps


# Part 2: the parser.
def readmailcapfile(fp):
 """Read a mailcap file and return a dictionary keyed by MIME type."""
 warnings.warn('readmailcapfile is deprecated, use getcaps instead',
 DeprecationWarning, 2)
 caps, _ = _readmailcapfile(fp, None)
 return caps


def _readmailcapfile(fp, lineno):
 """Read a mailcap file and return a dictionary keyed by MIME type.

 Each MIME type is mapped to an entry consisting of a list of
 dictionaries; the list will contain more than one such dictionary
 if a given MIME type appears more than once in the mailcap file.
 Each dictionary contains key-value pairs for that MIME type, where
 the viewing command is stored with the key "view".
 """
 caps = {}
 while 1:
 line = fp.readline()
 if not line: break
 # Ignore comments and blank lines
 if line[0] == '#' or line.strip() == '':
 continue
 nextline = line
 # Join continuation lines
 while nextline[-2:] == '\\\n':
 nextline = fp.readline()
 if not nextline: nextline = '\n'
 line = line[:-2] + nextline
 # Parse the line
 key, fields = parseline(line)
 if not (key and fields):
 continue
 if lineno is not None:
 fields['lineno'] = lineno
 lineno += 1
 # Normalize the key
 types = key.split('/')
 for j in range(len(types)):
 types[j] = types[j].strip()
 key = '/'.join(types).lower()
 # Update the database
 if key in caps:
 caps[key].append(fields)
 else:
 caps[key] = [fields]
 return caps, lineno

def parseline(line):
 """Parse one entry in a mailcap file and return a dictionary.

 The viewing command is stored as the value with the key "view",
 and the rest of the fields produce key-value pairs in the dict.
 """
 fields = []
 i, n = 0, len(line)
 while i < n:
 field, i = parsefield(line, i, n)
 fields.append(field)
 i = i+1 # Skip semicolon
 if len(fields) < 2:
 return None, None
 key, view, rest = fields[0], fields[1], fields[2:]
 fields = {'view': view}
 for field in rest:
 i = field.find('=')
 if i < 0:
 fkey = field
 fvalue = ""
 else:
 fkey = field[:i].strip()
 fvalue = field[i+1:].strip()
 if fkey in fields:
 # Ignore it
 pass
 else:
 fields[fkey] = fvalue
 return key, fields

def parsefield(line, i, n):
 """Separate one key-value pair in a mailcap entry."""
 start = i
 while i < n:
 c = line[i]
 if c == ';':
 break
 elif c == '\\':
 i = i+2
 else:
 i = i+1
 return line[start:i].strip(), i


# Part 3: using the database.

def findmatch(caps, MIMEtype, key='view', filename="/dev/null", plist=[]):
 """Find a match for a mailcap entry.

 Return a tuple containing the command line, and the mailcap entry
 used; (None, None) if no match is found. This may invoke the
 'test' command of several matching entries before deciding which
 entry to use.

 """
 entries = lookup(caps, MIMEtype, key)
 # XXX This code should somehow check for the needsterminal flag.
 for e in entries:
 if 'test' in e:
 test = subst(e['test'], filename, plist)
 if test and os.system(test) != 0:
 continue
 command = subst(e[key], MIMEtype, filename, plist)
 return command, e
 return None, None

def lookup(caps, MIMEtype, key=None):
 entries = []
 if MIMEtype in caps:
 entries = entries + caps[MIMEtype]
 MIMEtypes = MIMEtype.split('/')
 MIMEtype = MIMEtypes[0] + '/*'
 if MIMEtype in caps:
 entries = entries + caps[MIMEtype]
 if key is not None:
 entries = [e for e in entries if key in e]
 entries = sorted(entries, key=lineno_sort_key)
 return entries

def subst(field, MIMEtype, filename, plist=[]):
 # XXX Actually, this is Unix-specific
 res = ''
 i, n = 0, len(field)
 while i < n:
 c = field[i]; i = i+1
 if c != '%':
 if c == '\\':
 c = field[i:i+1]; i = i+1
 res = res + c
 else:
 c = field[i]; i = i+1
 if c == '%':
 res = res + c
 elif c == 's':
 res = res + filename
 elif c == 't':
 res = res + MIMEtype
 elif c == '{':
 start = i
 while i < n and field[i] != '}':
 i = i+1
 name = field[start:i]
 i = i+1
 res = res + findparam(name, plist)
 # XXX To do:
 # %n == number of parts if type is multipart/*
 # %F == list of alternating type and filename for parts
 else:
 res = res + '%' + c
 return res

def findparam(name, plist):
 name = name.lower() + '='
 n = len(name)
 for p in plist:
 if p[:n].lower() == name:
 return p[n:]
 return ''


# Part 4: test program.

def test():
 import sys
 caps = getcaps()
 if not sys.argv[1:]:
 show(caps)
 return
 for i in range(1, len(sys.argv), 2):
 args = sys.argv[i:i+2]
 if len(args) < 2:
 print("usage: mailcap [MIMEtype file] ...")
 return
 MIMEtype = args[0]
 file = args[1]
 command, e = findmatch(caps, MIMEtype, 'view', file)
 if not command:
 print("No viewer found for", type)
 else:
 print("Executing:", command)
 sts = os.system(command)
 if sts:
 print("Exit status:", sts)

def show(caps):
 print("Mailcap files:")
 for fn in listmailcapfiles(): print("\t" + fn)
 print()
 if not caps: caps = getcaps()
 print("Mailcap entries:")
 print()
 ckeys = sorted(caps)
 for type in ckeys:
 print(type)
 entries = caps[type]
 for e in entries:
 keys = sorted(e)
 for k in keys:
 print(" %-15s" % k, e[k])
 print()

if __name__ == '__main__':
 test()