#!/bin/sh -eu
#
# tgitui -- A terminal-based GIT log and stash viewer
#
# Copyright © 2021 Samuel Lidén Borell <samuel@kodafritt.se>
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
#


# TODO truncate long lines

esc=$(printf '\033')
enter=$(printf '\012')
ctrl_l=$(printf '\014')

redraw_list() {
    printf '\033[%d;1H' $start_row >&2
    i=0
    while [ $i != $height ]; do
        offsi=$((i + scroll))
        if [ $offsi -gt $max ]; then
            printf '\033[K\n' >&2
        else
            item=$(eval "printf '%s\n' \"\$item$offsi\"")
            if [ $offsi = $selected ]; then
                printf '  \033[7m %10s \033[0m\033[K\n' "$item" >&2
            else
                printf '   %s\033[K\n' "$item" >&2
            fi
        fi
        i=$((i + 1))
    done
    printf '\033[%d;4H' $((start_row + selected - scroll)) >&2
}

pipe_choice() {
    local selected=$(printf '%s\n' "$3" | cut -d ';' -f 1 | cut -d ':' -f 1)
    local scroll=$(printf '%s\n' "$3" | cut -d ';' -f 1 | cut -d ':' -f 2)
    # signals appear to be delayed
    #trap 'cols=$(tput cols); rows=$(tput lines); last=$((first + height - 1)); redraw_list' WINCH
    local cols=$(tput cols)
    local rows=$(tput lines)
    local start_row=$1
    local height=$((rows - $2))
    local i=0
    local first=$scroll
    local last=$((first + height - 1))
    printf '\033[%d;1H\033[2J' $start_row >&2
    while read item; do
        eval "local item$i=\$item"
        if [ $i = $selected ]; then
            printf '  \033[7m %s \033[0m\n' "$item" >&2
        elif [ $i -ge $first ] && [ $i -le $last ]; then
            printf '   %s\n' "$item" >&2
        fi
        i=$((i + 1))
    done
    printf '\033[%d;4H' $((start_row + selected - scroll)) >&2
    local max=$((i - 1))
    while true; do
        keyseq=$(dd bs=1 count=1 2>/dev/null <&3)
        case "$keyseq" in
        $enter)
            eval "printf '%s\n' \"$selected:$scroll;\$item$selected\""
            break;;
        q|Q)
            break;;
        $ctrl_l)
            cols=$(tput cols)
            rows=$(tput lines)
            last=$((first + height - 1))
            redraw_list >&2;;
        $esc)
            keyseq=$(dd bs=1 count=1 2>/dev/null <&3)
            case "$keyseq" in
            [)
                keyseq=$(dd bs=1 count=1 2>/dev/null <&3)
                case "$keyseq" in
                A) # Up key
                    [ $selected != 0 ] || continue
                    if [ $selected = $first ]; then
                        selected=$((selected - 1))
                        first=$((first - height))
                        last=$((last - height))
                        scroll=$((scroll - height))
                        redraw_list
                    else
                        row=$((start_row + selected-1 - scroll))
                        item=$(eval "printf '%s\n' \"\$item$selected\"")
                        selected=$((selected - 1))
                        previtem=$(eval "printf '%s\n' \"\$item$selected\"")
                        printf '\033[%d;1H  \033[7m %s \033[0m\033[K\n   %s \033[K\033[%d;4H' $row "$previtem" "$item" $row >&2
                    fi
                    ;;
                B) # Down key
                    [ $selected != $max ] || continue
                    if [ $selected = $last ]; then
                        selected=$((selected + 1))
                        first=$((first + height))
                        last=$((last + height))
                        scroll=$((scroll + height))
                        redraw_list
                    else
                        row=$((start_row + selected - scroll))
                        item=$(eval "printf '%s\n' \"\$item$selected\"")
                        selected=$((selected + 1))
                        nextitem=$(eval "printf '%s\n' \"\$item$selected\"")
                        printf '\033[%d;1H   %s\033[K\n  \033[7m %s \033[0m\033[K\033[%d;4H' $row "$item" "$nextitem" $((row+1)) >&2
                    fi
                    ;;
                1|H) # Home
                    [ $selected != 0 ] || continue
                    selected=0
                    first=0
                    last=$((height-1))
                    scroll=0
                    redraw_list
                    ;;
                4|F) # End
                    [ $selected != $max ] || continue
                    selected=$max
                    first=$((max - (max % height) ))
                    last=$((first + height-1))
                    scroll=$first
                    redraw_list
                    ;;
                5) # Page Up
                    [ $selected != 0 ] || continue
                    selected=$((selected - height))
                    if [ $selected -lt 0 ]; then
                        selected=0
                        first=0
                        last=$((height-1))
                        scroll=0
                    else
                        first=$((first - height))
                        last=$((last - height))
                        scroll=$((scroll - height))
                    fi
                    redraw_list
                    ;;
                6) # Page Down
                    [ $selected != $max ] || continue
                    selected=$((selected + height))
                    if [ $selected -gt $max ]; then
                        selected=$max
                        first=$((max - (max % height) ))
                        last=$((first + height-1))
                        scroll=$first
                    else
                        first=$((first + height))
                        last=$((last + height))
                        scroll=$((scroll + height))
                    fi
                    redraw_list
                    ;;
                #*)
                #    echo KEY:$keyseq >&2 ;;
                esac;;
            esac;;
        esac
    done
#    trap - WINCH
}


dummyitems() {
    cat <<EOF
Choice A
Choice B
Choice C
EOF
    ls -1 /usr/bin
}

setup_terminal() {
    printf '\033[?2004h\033(B\033)0\033[?1049h\033[1;1H' >&2
    saved_stty=$(stty -g)
    stty "$saved_stty"
    stty -echo -ctlecho -icanon
}

cleanup() {
    local rows=$(tput lines)
    printf '\033[%d;1H\033[?1049l\033[?1l\033[?2004l' $((rows-1)) >&2
    stty "$saved_stty"
}

find_git_root() {
    root='.'
    while [ ! -e "$root/.git" ] && [ x$(realpath "$root") != / ]; do
        root="$root/.."
    done
    echo "$root"
}

if [ $# -lt 1 ]; then
    cat <<EOF
usage: $0  SUBCOMMAND  [ARGUMENTS...]

Sub-commands:

add         Interactively add files
commits     Shows a log and allows the commits to be viewed
diff        Shows per-file diffs
stashed     Shows stashed commits

Sub-command names may be abbreviated as a/c/d/s

EOF
    exit 1
fi

# TODO factor out common code without breaking variables etc.
case "$1" in
a|add)
    shift
    trap cleanup EXIT
    setup_terminal
    liststate=0:0
    while true; do
        { sel=$( git status --porcelain=v1 "$@" | pipe_choice 2 3 "$liststate" ); } 3<&1
        if [ -z "$sel" ]; then break; fi
        liststate=$(printf '%s\n' "$sel" | cut -d ';' -f 1)
        file=$(printf '%s\n' "$sel" | cut -d ';' -f 2- | cut -d ' ' -f 2-)
        changetype=$(printf '%s\n' "$sel" | cut -d ';' -f 2- | cut -d ' ' -f 1)
        if [ "x$changetype" = xAM ]; then
            # Added + Unstaged changes --> Ask
            while true; do
                printf '\033[20G<-- [A]dd more or [U]stage this file? '
                case $(dd bs=1 count=1) in
                a|A)
                    changetype=M
                    break;;
                u|U)
                    changetype=A
                    break;;
                q|Q)
                    break 2;;
                esac
            done
        fi
        cleanup
        #echo "ch='$changetype' file='$file'">&2
        #read dummy
        case "$changetype" in
        M)
            # Modified, not added  --> Add
            git add -p "$file";;
        \?\?)
            # Untracked --> Add
            git add "$file";;
        A)
            # Added --> Unstage
            git rm --cached -f "$file";;
        *)
            echo "BUG: Don't know what to do with that file (changetype=$changetype)" >&2
        esac
        setup_terminal
    done;;
c|commits)
    shift
    trap cleanup EXIT
    setup_terminal
    liststate=0:0
    while true; do
        { sel=$( git log --oneline "$@" | pipe_choice 2 3 "$liststate" ); } 3<&1
        if [ -z "$sel" ]; then break; fi
        liststate=$(printf '%s\n' "$sel" | cut -d ';' -f 1)
        id=$(printf '%s\n' "$sel" | cut -d ';' -f 2- | cut -d ' ' -f 1)
        cleanup
        # it appears that GIT returns an error code when viewing the initial commit
        git show "$id" || true
        setup_terminal
    done;;
d|diff)
    shift
    trap cleanup EXIT
    setup_terminal
    liststate=0:0
    while true; do
        { sel=$( git diff --stat "$@" | head -n -1 | pipe_choice 2 3 "$liststate" ); } 3<&1
        if [ -z "$sel" ]; then break; fi
        liststate=$(printf '%s\n' "$sel" | cut -d ';' -f 1)
        file=$(printf '%s\n' "$sel" | cut -d ';' -f 2- | cut -d ' ' -f 1)
        cleanup
        git diff "$@" -- $(find_git_root)/"$file" || true
        setup_terminal
    done;;
s|stashed)
    shift
    trap cleanup EXIT
    setup_terminal
    liststate=0:0
    while true; do
        { sel=$( git stash list "$@" | pipe_choice 2 3 "$liststate" ); } 3<&1
        if [ -z "$sel" ]; then break; fi
        liststate=$(printf '%s\n' "$sel" | cut -d ';' -f 1)
        id=$(printf '%s\n' "$sel" | cut -d ';' -f 2- | cut -d ':' -f 1)
        cleanup
        git show "$id" || true
        setup_terminal
    done;;
*)
    echo "invalid sub-command: $1" >&2
    exit 1;;
esac