#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# SPDX-License-Identifier: GPL-2.0-or-later
# Copyright (C) 2020 by the Linux Foundation
#
__author__ = 'Konstantin Ryabitsev <konstantin@linuxfoundation.org>'

import os
import sys
import b4
import re
import email
import email.message
import email.policy
import json
import fnmatch

from string import Template
from email import utils
from pathlib import Path

logger = b4.logger

DEFAULT_PR_TEMPLATE = """
On ${sentdate}, ${fromname} wrote:
${quote}

Merged, thanks!

${summary}

Best regards,
-- 
${signature}
"""

DEFAULT_AM_TEMPLATE = """
On ${sentdate}, ${fromname} wrote:
${quote}

Applied, thanks!

${summary}

Best regards,
-- 
${signature}
"""

# Used to track commits created by current user
MY_COMMITS = None
# Used to track additional branch info
BRANCH_INFO = None
# Used to track mailmap replacements
MAILMAP_INFO = dict()


def git_get_merge_id(gitdir, commit_id, branch=None):
    # get merge commit id
    args = ['rev-list', '%s..' % commit_id, '--ancestry-path']
    if branch is not None:
        args += [branch]
    lines = b4.git_get_command_lines(gitdir, args)
    if not len(lines):
        return None
    return lines[-1]


def git_get_rev_diff(gitdir, rev):
    args = ['diff', '%s~..%s' % (rev, rev)]
    return b4.git_run_command(gitdir, args)


def git_get_commit_message(gitdir, rev):
    args = ['log', '--format=%B', '-1', rev]
    return b4.git_run_command(gitdir, args)


def fix_dests(addresses, excludes, gitdir):
    global MAILMAP_INFO
    for entry in list(addresses):
        # Check if it's in excludes
        removed = False
        for exclude in excludes:
            if fnmatch.fnmatch(entry[1], exclude):
                logger.debug('Removed %s due to matching %s', entry[1], exclude)
                addresses.remove(entry)
                removed = True
                break
        if removed:
            continue
        # Check if it's mailmap-replaced
        if entry[1] in MAILMAP_INFO:
            if MAILMAP_INFO[entry[1]]:
                addresses.remove(entry)
                addresses.append(MAILMAP_INFO[entry[1]])
            continue
        logger.debug('Checking if %s is mailmap-replaced', entry[1])
        args = ['check-mailmap', f'<{entry[1]}>']
        ecode, out = b4.git_run_command(gitdir, args)
        if ecode != 0:
            MAILMAP_INFO[entry[1]] = None
            continue
        replacement = utils.getaddresses([out.strip()])
        if len(replacement) == 1:
            if entry == replacement[0]:
                MAILMAP_INFO[entry[1]] = None
                continue
            logger.debug('Replaced %s with mailmap-updated %s', entry[1], replacement[0][1])
            MAILMAP_INFO[entry[1]] = replacement[0]
            addresses.remove(entry)
            addresses.append(replacement[0])

    return addresses


def make_reply(reply_template, jsondata, gitdir):
    body = Template(reply_template).safe_substitute(jsondata)
    # Conform to email standards
    body = body.replace('\n', '\r\n')
    msg = email.message_from_string(body)
    msg['From'] = '%s <%s>' % (jsondata['myname'], jsondata['myemail'])
    config = b4.get_main_config()
    # Remove ourselves and original sender from allto or allcc
    excludes = [jsondata['myemail'], jsondata['fromemail']]
    c_excludes = config.get('email-exclude')
    if c_excludes:
        for entry in c_excludes.split(','):
            excludes.append(entry.strip())

    allto = fix_dests(utils.getaddresses([jsondata['to']]), excludes, gitdir)
    allcc = fix_dests(utils.getaddresses([jsondata['cc']]), excludes, gitdir)

    # Add original sender to the To
    newto = fix_dests([(jsondata['fromname'], jsondata['fromemail'])], excludes[2:], gitdir)
    if newto:
        allto += newto

    msg.add_header('To', b4.format_addrs(allto))
    if allcc:
        msg.add_header('Cc', b4.format_addrs(allcc))
    msg['In-Reply-To'] = '<%s>' % jsondata['msgid']
    if len(jsondata['references']):
        msg['References'] = '%s <%s>' % (jsondata['references'], jsondata['msgid'])
    else:
        msg['References'] = '<%s>' % jsondata['msgid']

    subject = re.sub(r'^Re:\s+', '', jsondata['subject'], flags=re.I)
    if jsondata.get('cherrypick'):
        msg.add_header('Subject', 'Re: (subset) ' + subject)
    else:
        msg.add_header('Subject', 'Re: ' + subject)

    mydomain = jsondata['myemail'].split('@')[1]
    msg['Message-Id'] = email.utils.make_msgid(idstring='b4-ty', domain=mydomain)
    msg['Date'] = email.utils.formatdate(localtime=True)
    return msg


def auto_locate_pr(gitdir, jsondata, branch):
    pr_commit_id = jsondata['pr_commit_id']
    logger.debug('Checking %s', jsondata['pr_commit_id'])
    if not b4.git_commit_exists(gitdir, pr_commit_id):
        return None

    onbranches = b4.git_branch_contains(gitdir, pr_commit_id)
    if not len(onbranches):
        logger.debug('%s is not on any branches', pr_commit_id)
        return None
    if branch not in onbranches:
        logger.debug('%s is not on branch %s', pr_commit_id, branch)
        return None

    # Get the merge commit
    merge_commit_id = git_get_merge_id(gitdir, pr_commit_id, branch)
    if not merge_commit_id:
        logger.debug('Could not get a merge commit-id for %s', pr_commit_id)
        return None

    # Check that we are the author of the merge commit
    gitargs = ['show', '--format=%ae', merge_commit_id]
    out = b4.git_get_command_lines(gitdir, gitargs)
    if not out:
        logger.debug('Could not get merge commit author for %s', pr_commit_id)
        return None

    usercfg = b4.get_user_config()
    if usercfg['email'] not in out:
        logger.debug('Merged by a different author, ignoring %s', pr_commit_id)
        logger.debug('Author: %s', out[0])
        return None

    return merge_commit_id


def get_all_commits(gitdir, branch, since='1.week', committer=None):
    global MY_COMMITS
    if MY_COMMITS is not None:
        return MY_COMMITS

    MY_COMMITS = dict()
    if committer is None:
        usercfg = b4.get_user_config()
        committer = usercfg['email']

    gitargs = ['log', '--committer', committer, '--no-abbrev', '--oneline', '--since', since, branch]
    lines = b4.git_get_command_lines(gitdir, gitargs)
    if not len(lines):
        logger.debug('No new commits from the current user --since=%s', since)
        return MY_COMMITS

    logger.info('Found %s of your commits since %s', len(lines), since)
    logger.info('Calculating patch hashes, may take a moment...')
    # Get patch hash of each commit
    for line in lines:
        commit_id, subject = line.split(maxsplit=1)
        ecode, out = git_get_rev_diff(gitdir, commit_id)
        pwhash = b4.LoreMessage.get_patchwork_hash(out)
        logger.debug('phash=%s', pwhash)
        # get all message-id or link trailers
        ecode, out = git_get_commit_message(gitdir, commit_id)
        matches = re.findall(r'^\s*(?:message-id|link):[ \t]+(\S+)\s*$', out, flags=re.I | re.M)
        trackers = list()
        if matches:
            for tvalue in matches:
                trackers.append(tvalue)

        MY_COMMITS[pwhash] = (commit_id, subject, trackers)

    return MY_COMMITS


def auto_locate_series(gitdir, jsondata, branch, since='1.week'):
    commits = get_all_commits(gitdir, branch, since)

    patchids = set(commits.keys())
    # We need to find all of them in the commits
    found = list()
    matches = 0
    at = 0
    for patch in jsondata['patches']:
        at += 1
        logger.debug('Checking %s', patch)
        if patch[1] in patchids:
            logger.debug('Found: %s', patch[0])
            found.append((at, commits[patch[1]][0]))
            matches += 1
        else:
            # try to locate by subject
            success = False
            for pwhash, commit in commits.items():
                if commit[1] == patch[0]:
                    logger.debug('Matched using subject')
                    found.append((at, commit[0]))
                    success = True
                    matches += 1
                    break
                elif len(patch) > 2 and len(patch[2]) and len(commit[2]):
                    for tracker in commit[2]:
                        if tracker.find(patch[2]) >= 0:
                            logger.debug('Matched using recorded message-id')
                            found.append((at, commit[0]))
                            success = True
                            matches += 1
                            break
                if success:
                    break

            if not success:
                logger.debug('  Failed to find a match for: %s', patch[0])
                found.append((at, None))

    return found


def set_branch_details(gitdir, branch, jsondata, config):
    binfo = get_branch_info(gitdir, branch)
    jsondata['branch'] = branch
    for key, val in binfo.items():
        if key == 'b4-treename':
            config['thanks-treename'] = val
        elif key == 'b4-commit-url-mask':
            config['thanks-commit-url-mask'] = val
        elif key == 'b4-pr-template':
            config['thanks-pr-template'] = val
        elif key == 'b4-am-template':
            config['thanks-am-template'] = val
        elif key == 'branch':
            jsondata['branch'] = val

    if 'thanks-treename' in config:
        jsondata['treename'] = config['thanks-treename']
    elif 'url' in binfo:
        # noinspection PyBroadException
        try:
            # Try to grab the last two chunks of the path
            purl = Path(binfo['url'])
            jsondata['treename'] = os.path.join(purl.parts[-2], purl.parts[-1])
        except:
            # Something went wrong... just use the whole URL
            jsondata['treename'] = binfo['url']
    else:
        jsondata['treename'] = 'local tree'

    return jsondata, config


def generate_pr_thanks(gitdir, jsondata, branch):
    config = b4.get_main_config()
    jsondata, config = set_branch_details(gitdir, branch, jsondata, config)
    thanks_template = DEFAULT_PR_TEMPLATE
    if config['thanks-pr-template']:
        # Try to load this template instead
        try:
            thanks_template = b4.read_template(config['thanks-pr-template'])
        except FileNotFoundError:
            logger.critical('ERROR: thanks-pr-template says to use %s, but it does not exist',
                            config['thanks-pr-template'])
            sys.exit(2)

    if 'merge_commit_id' not in jsondata:
        merge_commit_id = git_get_merge_id(gitdir, jsondata['pr_commit_id'])
        if not merge_commit_id:
            logger.critical('Could not get merge commit id for %s', jsondata['subject'])
            logger.critical('Was it actually merged?')
            sys.exit(1)
        jsondata['merge_commit_id'] = merge_commit_id
    # Make a summary
    cidmask = config['thanks-commit-url-mask']
    if not cidmask:
        cidmask = 'merge commit: %s'
    jsondata['summary'] = cidmask % jsondata['merge_commit_id']
    msg = make_reply(thanks_template, jsondata, gitdir)
    return msg


def generate_am_thanks(gitdir, jsondata, branch, since):
    config = b4.get_main_config()
    jsondata, config = set_branch_details(gitdir, branch, jsondata, config)
    thanks_template = DEFAULT_AM_TEMPLATE
    if config['thanks-am-template']:
        # Try to load this template instead
        try:
            thanks_template = b4.read_template(config['thanks-am-template'])
        except FileNotFoundError:
            logger.critical('ERROR: thanks-am-template says to use %s, but it does not exist',
                            config['thanks-am-template'])
            sys.exit(2)
    if 'commits' not in jsondata:
        commits = auto_locate_series(gitdir, jsondata, branch, since)
    else:
        commits = jsondata['commits']

    cidmask = config['thanks-commit-url-mask']
    if not cidmask:
        cidmask = 'commit: %s'
    slines = list()
    nomatch = 0
    padlen = len(str(len(commits)))
    patches = jsondata['patches']
    for at, cid in commits:
        try:
            prefix = '[%s] ' % patches[at-1][3]
        except IndexError:
            prefix = '[%s/%s] ' % (str(at).zfill(padlen), len(commits))
        slines.append('%s%s' % (prefix, patches[at-1][0]))
        if cid is None:
            slines.append('%s(no commit info)' % (' ' * len(prefix)))
            nomatch += 1
        else:
            slines.append('%s%s' % (' ' * len(prefix), cidmask % cid))
    jsondata['summary'] = '\n'.join(slines)
    if nomatch == len(commits):
        logger.critical('  WARNING: None of the patches matched for: %s', jsondata['subject'])
        logger.critical('           Please review the resulting message')
    elif nomatch > 0:
        logger.critical('  WARNING: Could not match %s of %s patches in: %s',
                        nomatch, len(commits), jsondata['subject'])
        logger.critical('           Please review the resulting message')

    msg = make_reply(thanks_template, jsondata, gitdir)
    return msg


def auto_thankanator(cmdargs):
    gitdir = cmdargs.gitdir
    wantbranch = get_wanted_branch(cmdargs)
    logger.info('Auto-thankanating commits in %s', wantbranch)
    tracked = list_tracked()
    if not len(tracked):
        logger.info('Nothing to do')
        sys.exit(0)

    applied = list()
    for jsondata in tracked:
        if 'pr_commit_id' in jsondata:
            # this is a pull request
            merge_commit_id = auto_locate_pr(gitdir, jsondata, wantbranch)
            if merge_commit_id is None:
                continue
            jsondata['merge_commit_id'] = merge_commit_id
        else:
            # This is a patch series
            commits = auto_locate_series(gitdir, jsondata, wantbranch, since=cmdargs.since)
            # Weed out series that have no matches at all
            found = False
            for commit in commits:
                if commit[1] is not None:
                    found = True
                    break
            if not found:
                continue
            jsondata['commits'] = commits
        applied.append(jsondata)
        logger.info('  Located: %s', jsondata['subject'])

    if not len(applied):
        logger.info('Nothing to do')
        sys.exit(0)

    logger.info('---')
    send_messages(applied, wantbranch, cmdargs)
    sys.exit(0)


def send_messages(listing, branch, cmdargs):
    logger.info('Generating %s thank-you letters', len(listing))
    gitdir = cmdargs.gitdir
    datadir = b4.get_data_dir()
    fromaddr = None
    if cmdargs.sendemail:
        # See if we have sendemail-identity set
        config = b4.get_main_config()
        identity = config.get('sendemail-identity')
        try:
            smtp, fromaddr = b4.get_smtp(identity)
        except Exception as ex:  # noqa
            logger.critical('Failed to configure the smtp connection:')
            logger.critical(ex)
            sys.exit(1)
    else:
        # We write .thanks notes
        # Check if the outdir exists and if it has any .thanks files in it
        if not os.path.exists(cmdargs.outdir):
            os.mkdir(cmdargs.outdir)

    usercfg = b4.get_user_config()
    # Do we have a .signature file?
    sigfile = os.path.join(str(Path.home()), '.signature')
    if os.path.exists(sigfile):
        with open(sigfile, 'r', encoding='utf-8') as fh:
            signature = fh.read()
    else:
        signature = '%s <%s>' % (usercfg['name'], usercfg['email'])

    outgoing = 0
    for jsondata in listing:
        jsondata['myname'] = usercfg['name']
        jsondata['myemail'] = usercfg['email']
        jsondata['signature'] = signature
        if 'pr_commit_id' in jsondata:
            # This is a pull request
            msg = generate_pr_thanks(gitdir, jsondata, branch)
        else:
            # This is a patch series
            msg = generate_am_thanks(gitdir, jsondata, branch, cmdargs.since)

        if msg is None:
            continue

        outgoing += 1
        msg.set_charset('utf-8')
        msg.replace_header('Content-Transfer-Encoding', '8bit')
        if cmdargs.sendemail:
            msg.policy = email.policy.EmailPolicy(utf8=True, cte_type='8bit')
            emldata = msg.as_string()
            if not fromaddr:
                fromaddr = jsondata['myemail']
            if cmdargs.dryrun:
                logger.info('--- DRYRUN: message follows ---')
                logger.info('\t' + emldata.replace('\n', '\n\t'))
                logger.info('--- DRYRUN: message ends ---')
            else:
                alldests = email.utils.getaddresses([str(x) for x in msg.get_all('to', [])])
                alldests += email.utils.getaddresses([str(x) for x in msg.get_all('cc', [])])
                sendto = {x[1] for x in alldests}
                logger.info('  Sending: %s', msg.get('subject'))
                # Python's sendmail implementation seems to have some logic problems where 8-bit messages are involved.
                # As far as I understand the difference between 8BITMIME (supported by nearly all smtp servers) and
                # SMTPUTF8 (supported by very few), SMTPUTF8 is only required when the addresses specified in either
                # "MAIL FROM" or "RCPT TO" lines of the _protocol exchange_ themselves have 8bit characters, not
                # anything in the From: header of the DATA payload. Python's smtplib seems to always try to encode
                # strings as ascii regardless of what was policy was specified.
                # Work around this by getting the payload as string and then encoding to bytes ourselves.
                # Force compliant eols
                emldata = re.sub(r'(?:\r\n|\n|\r(?!\n))', '\r\n', emldata) # noqa
                smtp.sendmail(fromaddr, sendto, emldata.encode())  # noqa
        else:
            slug_from = re.sub(r'\W', '_', jsondata['fromemail'])
            slug_subj = re.sub(r'\W', '_', jsondata['subject'])
            slug = '%s_%s' % (slug_from.lower(), slug_subj.lower())
            slug = re.sub(r'_+', '_', slug)
            outfile = os.path.join(cmdargs.outdir, '%s.thanks' % slug)
            logger.info('  Writing: %s', outfile)
            with open(outfile, 'w') as fh:
                fh.write(msg.as_string(policy=b4.emlpolicy))
        if cmdargs.dryrun:
            logger.info('Dry run, preserving tracked series.')
        else:
            logger.debug('Cleaning up: %s', jsondata['trackfile'])
            fullpath = os.path.join(datadir, jsondata['trackfile'])
            os.rename(fullpath, '%s.sent' % fullpath)

    logger.info('---')
    if not outgoing:
        logger.info('No thanks necessary.')
        return

    if cmdargs.sendemail:
        if cmdargs.dryrun:
            logger.info('DRYRUN: generated %s thank-you letters', outgoing)
        else:
            logger.info('Sent %s thank-you letters', outgoing)
        smtp.quit()
    else:
        logger.debug('Wrote %s thank-you letters', outgoing)
        logger.info('You can now run:')
        logger.info('  git send-email %s/*.thanks', cmdargs.outdir)


def list_tracked():
    # find all tracked bits
    tracked = list()
    datadir = b4.get_data_dir()
    paths = sorted(Path(datadir).iterdir(), key=os.path.getmtime)
    for fullpath in paths:
        if fullpath.suffix not in ('.pr', '.am'):
            continue
        with fullpath.open('r', encoding='utf-8') as fh:
            jsondata = json.load(fh)
            jsondata['trackfile'] = fullpath.name
            if fullpath.suffix == '.pr':
                jsondata['pr_commit_id'] = fullpath.stem
        tracked.append(jsondata)
    return tracked


def write_tracked(tracked):
    counter = 1
    config = b4.get_main_config()
    logger.info('Currently tracking:')
    for entry in tracked:
        logger.info('%3d: %s', counter, entry['subject'])
        logger.info('       From: %s <%s>', entry['fromname'], entry['fromemail'])
        logger.info('       Date: %s', entry['sentdate'])
        logger.info('       Link: %s', config['linkmask'] % entry['msgid'])
        counter += 1


def thank_selected(cmdargs):
    tracked = list_tracked()
    if not len(tracked):
        logger.info('Nothing to do')
        sys.exit(0)

    if cmdargs.thankfor == 'all':
        listing = tracked
    else:
        listing = list()
        for num in b4.parse_int_range(cmdargs.thankfor, upper=len(tracked)):
            try:
                index = int(num) - 1
                listing.append(tracked[index])
            except ValueError:
                logger.critical('Please provide the number of the message')
                logger.info('---')
                write_tracked(tracked)
                sys.exit(1)
            except IndexError:
                logger.critical('Invalid index: %s', num)
                logger.info('---')
                write_tracked(tracked)
                sys.exit(1)
    if not len(listing):
        logger.info('Nothing to do')
        sys.exit(0)

    wantbranch = get_wanted_branch(cmdargs)
    send_messages(listing, wantbranch, cmdargs)
    sys.exit(0)


def discard_selected(cmdargs):
    tracked = list_tracked()
    if not len(tracked):
        logger.info('Nothing to do')
        sys.exit(0)

    if cmdargs.discard == 'all':
        listing = tracked
    else:
        listing = list()
        for num in b4.parse_int_range(cmdargs.discard, upper=len(tracked)):
            try:
                index = int(num) - 1
                listing.append(tracked[index])
            except ValueError:
                logger.critical('Please provide the number of the message')
                logger.info('---')
                write_tracked(tracked)
                sys.exit(1)
            except IndexError:
                logger.critical('Invalid index: %s', num)
                logger.info('---')
                write_tracked(tracked)
                sys.exit(1)

    if not len(listing):
        logger.info('Nothing to do')
        sys.exit(0)

    datadir = b4.get_data_dir()
    logger.info('Discarding %s messages', len(listing))
    for jsondata in listing:
        fullpath = os.path.join(datadir, jsondata['trackfile'])
        os.rename(fullpath, '%s.discarded' % fullpath)
        logger.info('  Discarded: %s', jsondata['subject'])

    sys.exit(0)


def check_stale_thanks(outdir):
    if os.path.exists(outdir):
        for entry in Path(outdir).iterdir():
            if entry.suffix == '.thanks':
                logger.critical('ERROR: Found existing .thanks files in: %s', outdir)
                logger.critical('       Please send them first (or delete if already sent).')
                logger.critical('       Refusing to run to avoid potential confusion.')
                sys.exit(1)


def get_wanted_branch(cmdargs):
    global BRANCH_INFO
    gitdir = cmdargs.gitdir
    if not cmdargs.branch:
        # Find out our current branch
        gitargs = ['symbolic-ref', '-q', 'HEAD']
        ecode, out = b4.git_run_command(gitdir, gitargs)
        if ecode > 0:
            logger.critical('Not able to get current branch (git symbolic-ref HEAD)')
            sys.exit(1)
        wantbranch = re.sub(r'^refs/heads/', '', out.strip())
        logger.debug('will check branch=%s', wantbranch)
    else:
        # Make sure it's a real branch
        gitargs = ['branch', '--format=%(refname)', '--list', '--all', cmdargs.branch]
        lines = b4.git_get_command_lines(gitdir, gitargs)
        if not len(lines):
            logger.critical('Requested branch not found in git branch --list --all %s', cmdargs.branch)
            sys.exit(1)
        wantbranch = cmdargs.branch

    return wantbranch


def get_branch_info(gitdir, branch):
    global BRANCH_INFO
    if BRANCH_INFO is not None:
        return BRANCH_INFO

    BRANCH_INFO = dict()

    remotecfg = b4.get_config_from_git('branch\\.%s\\.*' % branch)
    if remotecfg is None or 'remote' not in remotecfg:
        # Did not find a matching branch entry, so look at remotes
        gitargs = ['remote', 'show']
        lines = b4.git_get_command_lines(gitdir, gitargs)
        if not len(lines):
            # No remotes? Hmm...
            return BRANCH_INFO

        remote = None
        for entry in lines:
            if branch.find(f'{entry}/') == 0:
                remote = entry
                break

        if remote is None:
            # Not found any matching remotes
            return BRANCH_INFO

        BRANCH_INFO['remote'] = remote
        BRANCH_INFO['branch'] = branch.replace(f'{remote}/', '')

    else:
        BRANCH_INFO['remote'] = remotecfg['remote']
        if 'merge' in remotecfg:
            BRANCH_INFO['branch'] = re.sub(r'^refs/heads/', '', remotecfg['merge'])

    # Grab template overrides
    remotecfg = b4.get_config_from_git('remote\\.%s\\..*' % BRANCH_INFO['remote'])
    BRANCH_INFO.update(remotecfg)

    return BRANCH_INFO


def main(cmdargs):
    usercfg = b4.get_user_config()
    if 'email' not in usercfg:
        logger.critical('Please set user.email in gitconfig to use this feature.')
        sys.exit(1)

    if cmdargs.auto:
        check_stale_thanks(cmdargs.outdir)
        auto_thankanator(cmdargs)
    elif cmdargs.thankfor:
        check_stale_thanks(cmdargs.outdir)
        thank_selected(cmdargs)
    elif cmdargs.discard:
        discard_selected(cmdargs)
    else:
        tracked = list_tracked()
        if not len(tracked):
            logger.info('No thanks necessary.')
            sys.exit(0)
        write_tracked(tracked)
        logger.info('---')
        logger.info('You can send them using number ranges, e.g:')
        logger.info('  b4 ty -t 1-3,5,7-')