#!/bin/bash

if [ "$#" -lt 1 ]; then
        printf 'Usage: %s <commit range>\n', "$0" 1>&2
        exit 1
fi

commits=$(git rev-list --no-merges -i --grep='^[[:space:]]*Fixes:' "$@")
if [ -z "$commits" ]; then
        exit 0
fi

# This should be a git tree that contains *only* Linus' tree
Linus_tree="${HOME}/kernels/linus.git"

split_re='^([Cc][Oo][Mm][Mm][Ii][Tt])?[[:space:]]*([[:xdigit:]]{5,})([[:space:]]*)(.*)$'
nl=$'\n'

# Strip the leading and training spaces from a string
strip_spaces()
{
	[[ "$1" =~ ^[[:space:]]*(.*[^[:space:]])[[:space:]]*$ ]]
	echo "${BASH_REMATCH[1]}"
}

for c in $commits; do

	commit_log=$(git log -1 --format='%h ("%s")' "$c")
	commit_msg="In commit

  $commit_log

"

	fixes_lines=$(git log -1 --format='%B' "$c" |
			grep -i '^[[:space:]]*Fixes:')

	while read -r fline; do
		[[ "$fline" =~ ^[[:space:]]*[Ff][Ii][Xx][Ee][Ss]:[[:space:]]*(.*)$ ]]
		f="${BASH_REMATCH[1]}"
		fixes_msg="Fixes tag

  $fline

has these problem(s):

"
		sha=
		subject=
		msg=
		if [[ "$f" =~ $split_re ]]; then
			first="${BASH_REMATCH[1]}"
			sha="${BASH_REMATCH[2]}"
			spaces="${BASH_REMATCH[3]}"
			subject="${BASH_REMATCH[4]}"
			if [ "$first" ]; then
				msg="${msg:+${msg}${nl}}  - leading word '$first' unexpected"
			fi
			if [ -z "$subject" ]; then
				msg="${msg:+${msg}${nl}}  - missing subject"
			elif [ -z "$spaces" ]; then
				msg="${msg:+${msg}${nl}}  - missing space between the SHA1 and the subject"
			fi
		else
			printf '%s%s  - %s\n' "$commit_msg" "$fixes_msg" 'No SHA1 recognised'
			commit_msg=''
			continue
		fi
		if ! git rev-parse -q --verify "$sha" >/dev/null; then
			printf '%s%s  - %s\n' "$commit_msg" "$fixes_msg" 'Target SHA1 does not exist'
			commit_msg=''
			continue
		fi

		if [ "${#sha}" -lt 12 ]; then
			msg="${msg:+${msg}${nl}}  - SHA1 should be at least 12 digits long${nl}    Can be fixed by setting core.abbrev to 12 (or more) or (for git v2.11${nl}    or later) just making sure it is not set (or set to \"auto\")."
		fi
		# reduce the subject to the part between () if there
		if [[ "$subject" =~ ^\((.*)\) ]]; then
			subject="${BASH_REMATCH[1]}"
		elif [[ "$subject" =~ ^\((.*) ]]; then
			subject="${BASH_REMATCH[1]}"
			msg="${msg:+${msg}${nl}}  - Subject has leading but no trailing parentheses"
		fi

		# strip matching quotes at the start and end of the subject
		# the unicode characters in the classes are
		# U+201C LEFT DOUBLE QUOTATION MARK
		# U+201D RIGHT DOUBLE QUOTATION MARK
		# U+2018 LEFT SINGLE QUOTATION MARK
		# U+2019 RIGHT SINGLE QUOTATION MARK
		re1=$'^[\"\u201C](.*)[\"\u201D]$'
		re2=$'^[\'\u2018](.*)[\'\u2019]$'
		re3=$'^[\"\'\u201C\u2018](.*)$'
		if [[ "$subject" =~ $re1 ]]; then
			subject="${BASH_REMATCH[1]}"
		elif [[ "$subject" =~ $re2 ]]; then
			subject="${BASH_REMATCH[1]}"
		elif [[ "$subject" =~ $re3 ]]; then
			subject="${BASH_REMATCH[1]}"
			msg="${msg:+${msg}${nl}}  - Subject has leading but no trailing quotes"
		fi

		subject=$(strip_spaces "$subject")

		target_subject=$(git log -1 --format='%s' "$sha")
		target_subject=$(strip_spaces "$target_subject")

		# match with ellipses
		case "$subject" in
		*...)	subject="${subject%...}"
			target_subject="${target_subject:0:${#subject}}"
			;;
		...*)	subject="${subject#...}"
			target_subject="${target_subject: -${#subject}}"
			;;
		*\ ...\ *)
			s1="${subject% ... *}"
			s2="${subject#* ... }"
			subject="$s1 $s2"
			t1="${target_subject:0:${#s1}}"
			t2="${target_subject: -${#s2}}"
			target_subject="$t1 $t2"
			;;
		esac
		subject=$(strip_spaces "$subject")
		target_subject=$(strip_spaces "$target_subject")

		if [ "$subject" != "${target_subject:0:${#subject}}" ]; then
			msg="${msg:+${msg}${nl}}  - Subject does not match target commit subject"
		fi
		lsha=$(cd "$Linus_tree" && git rev-parse -q --verify "$sha")
		if [ -z "$lsha" ]; then
			count=$(git rev-list --count "$sha".."$c")
			if [ "$count" -eq 0 ]; then
				msg="${msg:+${msg}${nl}}  - Target is not an ancestor of this commit"
			fi
		fi
		if [ "$msg" ]; then
			printf '%s%s%s\n' "$commit_msg" "$fixes_msg" "$msg"
			commit_msg=''
		fi
	done <<< "$fixes_lines"
done

exit 0
