#!/usr/bin/env zsh
## Author:  druckdev
## Created: 2020-08-28
##
## A TUI for git-log using fzf.
## Displays git-log in fzf and git-show as preview command for each commit.

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

# Return if fzf is not available
if ! command -v fzf &>/dev/null; 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'
# Verbose format for the preview window on the right
# This array is stitched together with newlines later
local -a format=(
	'--pretty=format:%C(yellow)'     # newline created by this eaten by %-
	'%-Commit:      %H%C(auto)'      # yellow commit hash
	'             %D%Cblue'          # auto colored ref names (if any)
	'Author:      %aN %aE%Cred'      # blue author mail
	'AuthorDate:  %ad%Cblue'         # red author date
	'Commit:      %cN %cE%Cred'      # blue commiter mail
	'CommitDate:  %cd%Cblue'         # red commit date
	'Signer:      %GS%Cgreen'        # signer name
	'Key (%G?):     %GK'             # pgp key used to sign
	'%Creset%C(bold)'                # empty line
	'    %s%Creset'                  # bold white subject
	''                               # newline
	'%-b'                            # body
	''                               # newline
)

# Ignore the graph part at the beginning, then capture the commit hash and throw
# away the rest of the line.
local commit_hash='s/^[^a-f0-9]*([a-f0-9]*).*$/\1/'

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

local -A fzf_preview
read -r -d '' <<EOT
	out="\$(echo -E {} | sed -E "$commit_hash")"; [[ -z "\$out" ]] ||
EOT
fzf_preview[construct]="$REPLY"

read -r -d '' <<EOT
	git show "${(j:%n:)format}" "$date" --color=always --patch-with-stat "\$out"
EOT
fzf_preview[patch]="$fzf_preview[construct] { $REPLY"
if command -v diff-so-fancy &>/dev/null; then
	fzf_preview[patch]+=" | diff-so-fancy --color=always"
fi
fzf_preview[patch]+=" }"

read -r -d '' <<EOT
	git show "${(j:%n:)format}" "$date" --color=always --stat "\$out"
EOT
fzf_preview[stat]="$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 ]] && command -v pbcopy &>/dev/null; then
	fzf_copy_command+=" | pbcopy"
elif command -v xclip &>/dev/null; then
	fzf_copy_command+=" | xclip -selection c"
fi

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[patch] | command less -R@"
	# Clear query if not empty, abort otherwise
	"esc" "cancel"
	# Preview stats
	"ctrl-s" "preview($fzf_preview[stat])"
	# Preview patch
	"ctrl-d" "preview($fzf_preview[patch])"
	"ctrl-p" "preview($fzf_preview[patch])"
)
local -a fzf_args=(
	# Understand ansi color escape sequences.
	"--ansi"
	# Expand the binds array in the format "key1:value1,key2:value2".
	"--bind" "${(@kj:,:)binds/(#m)*/$MATCH:$binds[$MATCH]}"
	# Execute git show on the commit as preview.
	"--preview" "$fzf_preview[patch]"
	# 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 log --all "$formatshort" --graph "$dateshort" --color=always "$@" \
| fzf "${fzf_args[@]}"
return 0