#!/usr/bin/env zsh
## Author:  druckdev
## Created: 2021-05-15
##
## A TUI for displaying branches using fzf.
## Displays `git branch -a` in fzf and git-log as preview for each branch.

# extendedglob is necessary for the expansion of the binds array
emulate -L zsh -o extendedglob

# Return if fzf is not available
if (( ! $+commands[fzf] )); then
	printf "command not found: fzf" >&2
	return 1
fi

# Return if not in git repo
git rev-parse || return

# One line format for fzf list view
# abbreviated commit hash (yellow), title and ref names
local formatshort='--pretty=format:%C(yellow)%h %Creset%s%C(auto)%d'

local dateshort='--date=format:%F' # year
local date="$dateshort %T %z" # year time timezone

local -A fzf_preview
read -r -d '' <<EOT
	out="\$(echo -En {} | cut -c3- | cut -d' ' -f1)"; [[ -z "\$out" ]] ||
EOT
fzf_preview[construct]="$REPLY"

read -r -d '' <<EOT
	git log "$formatshort" --graph "$dateshort" --color=always "\$out"
EOT
fzf_preview[log]="$fzf_preview[construct] { $REPLY }"

# Put the commit hash into the clipboard
# (If no known clipboard tool is available, just print it)
local fzf_copy_command="$fzf_preview[construct] echo -n \"\$out\""
if [[ $OSTYPE =~ darwin ]] && (( $+commands[pbcopy] )); then
	fzf_copy_command+=" | pbcopy"
elif (( $+commands[xclip] )); then
	fzf_copy_command+=" | xclip -selection c"
fi

# Get directory of this file
# (When using the autoloaded function or executing this file directly)
local AUTOLOAD_DIR="${${functions_source[${0:t}]:-$0}:A:h}"

local -A binds=(
	"ctrl-space" "toggle-preview"
	"ctrl-alt-j" "preview-down"
	"ctrl-alt-k" "preview-up"
	# Copy commit hash
	"ctrl-y" "execute@$fzf_copy_command@"
	# Open preview "fullscreen"
	"enter" "execute@$fzf_preview[construct] "$AUTOLOAD_DIR"/glog \"\$out\"@"
	# Clear query if not empty, abort otherwise
	"esc" "cancel"
)
local -a fzf_args=(
	# Understand ansi color escape sequences.
	"--ansi"
	# Expand the binds array in the format "key1:value1,key2:value2".
	"--bind" "${(@kj:,:)binds/(#m)*/$MATCH:$binds[$MATCH]}"
	# Execute git show on the commit as preview.
	"--preview" "$fzf_preview[log]"
	# Reverse the layout so that the newest commit is at the top.
	"--reverse"
	# Do not sort when typing to maintain the sorting by date.
	"--no-sort"
)

# The preview-window should be placed differently depending on the dimensions of
# the terminal.
# 0.45 seems to be round about the ratio between cols and lines on my system.
# With that I get somewhat decent results with. This probably depends on the
# font and font-size of the terminal and needs to be changed potentially.
local -a tty_size
tty_size=(${=$(command stty size 2>/dev/null)})
if (( ! $? )) && (( $tty_size[2] * 0.4 > $tty_size[1] )); then
	fzf_args+=(--preview-window=right)
else
	fzf_args+=(--preview-window=down)
fi

# Display an ascii graph of the commits in the above format and pipe that into
# fzf.
git branch -a --color=always "$@" \
| fzf "${fzf_args[@]}"
return 0