#!/bin/sh
# git-mergetool--lib is a library for common merge tool functions
MERGE_TOOLS_DIR=$(git --exec-path)/mergetools

mode_ok () {
        if diff_mode
        then
                can_diff
        elif merge_mode
        then
                can_merge
        else
                false
        fi
}

is_available () {
        merge_tool_path=$(translate_merge_tool_path "$1") &&
        type "$merge_tool_path" >/dev/null 2>&1
}

list_config_tools () {
        section=$1
        line_prefix=${2:-}

        git config --get-regexp $section'\..*\.cmd' |
        while read -r key value
        do
                toolname=${key#$section.}
                toolname=${toolname%.cmd}

                printf "%s%s\n" "$line_prefix" "$toolname"
        done
}

show_tool_names () {
        condition=${1:-true} per_line_prefix=${2:-} preamble=${3:-}
        not_found_msg=${4:-}
        extra_content=${5:-}

        shown_any=
        ( cd "$MERGE_TOOLS_DIR" && ls ) | {
                while read toolname
                do
                        if setup_tool "$toolname" 2>/dev/null &&
                                (eval "$condition" "$toolname")
                        then
                                if test -n "$preamble"
                                then
                                        printf "%s\n" "$preamble"
                                        preamble=
                                fi
                                shown_any=yes
                                printf "%s%s\n" "$per_line_prefix" "$toolname"
                        fi
                done

                if test -n "$extra_content"
                then
                        if test -n "$preamble"
                        then
                                # Note: no '\n' here since we don't want a
                                # blank line if there is no initial content.
                                printf "%s" "$preamble"
                                preamble=
                        fi
                        shown_any=yes
                        printf "\n%s\n" "$extra_content"
                fi

                if test -n "$preamble" && test -n "$not_found_msg"
                then
                        printf "%s\n" "$not_found_msg"
                fi

                test -n "$shown_any"
        }
}

diff_mode() {
        test "$TOOL_MODE" = diff
}

merge_mode() {
        test "$TOOL_MODE" = merge
}

translate_merge_tool_path () {
        echo "$1"
}

check_unchanged () {
        if test "$MERGED" -nt "$BACKUP"
        then
                status=0
        else
                while true
                do
                        echo "$MERGED seems unchanged."
                        printf "Was the merge successful? [y/n] "
                        read answer || return 1
                        case "$answer" in
                        y*|Y*) status=0; break ;;
                        n*|N*) status=1; break ;;
                        esac
                done
        fi
}

valid_tool () {
        setup_tool "$1" && return 0
        cmd=$(get_merge_tool_cmd "$1")
        test -n "$cmd"
}

setup_tool () {
        tool="$1"

        # Fallback definitions, to be overriden by tools.
        can_merge () {
                return 0
        }

        can_diff () {
                return 0
        }

        diff_cmd () {
                status=1
                return $status
        }

        merge_cmd () {
                status=1
                return $status
        }

        translate_merge_tool_path () {
                echo "$1"
        }

        if ! test -f "$MERGE_TOOLS_DIR/$tool"
        then
                # Use a special return code for this case since we want to
                # source "defaults" even when an explicit tool path is
                # configured since the user can use that to override the
                # default path in the scriptlet.
                return 2
        fi

        # Load the redefined functions
        . "$MERGE_TOOLS_DIR/$tool"

        if merge_mode && ! can_merge
        then
                echo "error: '$tool' can not be used to resolve merges" >&2
                return 1
        elif diff_mode && ! can_diff
        then
                echo "error: '$tool' can only be used to resolve merges" >&2
                return 1
        fi
        return 0
}

get_merge_tool_cmd () {
        merge_tool="$1"
        if diff_mode
        then
                git config "difftool.$merge_tool.cmd" ||
                git config "mergetool.$merge_tool.cmd"
        else
                git config "mergetool.$merge_tool.cmd"
        fi
}

# Entry point for running tools
run_merge_tool () {
        # If GIT_PREFIX is empty then we cannot use it in tools
        # that expect to be able to chdir() to its value.
        GIT_PREFIX=${GIT_PREFIX:-.}
        export GIT_PREFIX

        merge_tool_path=$(get_merge_tool_path "$1") || exit
        base_present="$2"
        status=0

        # Bring tool-specific functions into scope
        setup_tool "$1"
        exitcode=$?
        case $exitcode in
        0)
                :
                ;;
        2)
                # The configured tool is not a built-in tool.
                test -n "$merge_tool_path" || return 1
                ;;
        *)
                return $exitcode
                ;;
        esac

        if merge_mode
        then
                run_merge_cmd "$1"
        else
                run_diff_cmd "$1"
        fi
        return $status
}

# Run a either a configured or built-in diff tool
run_diff_cmd () {
        merge_tool_cmd=$(get_merge_tool_cmd "$1")
        if test -n "$merge_tool_cmd"
        then
                ( eval $merge_tool_cmd )
                status=$?
                return $status
        else
                diff_cmd "$1"
        fi
}

# Run a either a configured or built-in merge tool
run_merge_cmd () {
        merge_tool_cmd=$(get_merge_tool_cmd "$1")
        if test -n "$merge_tool_cmd"
        then
                trust_exit_code=$(git config --bool \
                        "mergetool.$1.trustExitCode" || echo false)
                if test "$trust_exit_code" = "false"
                then
                        touch "$BACKUP"
                        ( eval $merge_tool_cmd )
                        status=$?
                        check_unchanged
                else
                        ( eval $merge_tool_cmd )
                        status=$?
                fi
                return $status
        else
                merge_cmd "$1"
        fi
}

list_merge_tool_candidates () {
        if merge_mode
        then
                tools="tortoisemerge"
        else
                tools="kompare"
        fi
        if test -n "$DISPLAY"
        then
                if test -n "$GNOME_DESKTOP_SESSION_ID"
                then
                        tools="meld opendiff kdiff3 tkdiff xxdiff $tools"
                else
                        tools="opendiff kdiff3 tkdiff xxdiff meld $tools"
                fi
                tools="$tools gvimdiff diffuse ecmerge p4merge araxis bc3 codecompare"
        fi
        case "${VISUAL:-$EDITOR}" in
        *vim*)
                tools="$tools vimdiff emerge"
                ;;
        *)
                tools="$tools emerge vimdiff"
                ;;
        esac
}

show_tool_help () {
        tool_opt="'git ${TOOL_MODE}tool --tool-<tool>'"

        tab='   '
        LF='
'
        any_shown=no

        cmd_name=${TOOL_MODE}tool
        config_tools=$({
                diff_mode && list_config_tools difftool "$tab$tab"
                list_config_tools mergetool "$tab$tab"
        } | sort)
        extra_content=
        if test -n "$config_tools"
        then
                extra_content="${tab}user-defined:${LF}$config_tools"
        fi

        show_tool_names 'mode_ok && is_available' "$tab$tab" \
                "$tool_opt may be set to one of the following:" \
                "No suitable tool for 'git $cmd_name --tool=<tool>' found." \
                "$extra_content" &&
                any_shown=yes

        show_tool_names 'mode_ok && ! is_available' "$tab$tab" \
                "${LF}The following tools are valid, but not currently available:" &&
                any_shown=yes

        if test "$any_shown" = yes
        then
                echo
                echo "Some of the tools listed above only work in a windowed"
                echo "environment. If run in a terminal-only session, they will fail."
        fi
        exit 0
}

guess_merge_tool () {
        list_merge_tool_candidates
        cat >&2 <<-EOF

        This message is displayed because '$TOOL_MODE.tool' is not configured.
        See 'git ${TOOL_MODE}tool --tool-help' or 'git help config' for more details.
        'git ${TOOL_MODE}tool' will now attempt to use one of the following tools:
        $tools
        EOF

        # Loop over each candidate and stop when a valid merge tool is found.
        for tool in $tools
        do
                is_available "$tool" && echo "$tool" && return 0
        done

        echo >&2 "No known ${TOOL_MODE} tool is available."
        return 1
}

get_configured_merge_tool () {
        # Diff mode first tries diff.tool and falls back to merge.tool.
        # Merge mode only checks merge.tool
        if diff_mode
        then
                merge_tool=$(git config diff.tool || git config merge.tool)
        else
                merge_tool=$(git config merge.tool)
        fi
        if test -n "$merge_tool" && ! valid_tool "$merge_tool"
        then
                echo >&2 "git config option $TOOL_MODE.tool set to unknown tool: $merge_tool"
                echo >&2 "Resetting to default..."
                return 1
        fi
        echo "$merge_tool"
}

get_merge_tool_path () {
        # A merge tool has been set, so verify that it's valid.
        merge_tool="$1"
        if ! valid_tool "$merge_tool"
        then
                echo >&2 "Unknown merge tool $merge_tool"
                exit 1
        fi
        if diff_mode
        then
                merge_tool_path=$(git config difftool."$merge_tool".path ||
                                  git config mergetool."$merge_tool".path)
        else
                merge_tool_path=$(git config mergetool."$merge_tool".path)
        fi
        if test -z "$merge_tool_path"
        then
                merge_tool_path=$(translate_merge_tool_path "$merge_tool")
        fi
        if test -z "$(get_merge_tool_cmd "$merge_tool")" &&
                ! type "$merge_tool_path" >/dev/null 2>&1
        then
                echo >&2 "The $TOOL_MODE tool $merge_tool is not available as"\
                         "'$merge_tool_path'"
                exit 1
        fi
        echo "$merge_tool_path"
}

get_merge_tool () {
        # Check if a merge tool has been configured
        merge_tool=$(get_configured_merge_tool)
        # Try to guess an appropriate merge tool if no tool has been set.
        if test -z "$merge_tool"
        then
                merge_tool=$(guess_merge_tool) || exit
        fi
        echo "$merge_tool"
}