#!/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.

# TODO: preview breaks when files were passed but they were renamed and have a
# different name at the point of this commit

# 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'
# 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] { $REPLY"
# Get file arguments after (and including) `--` and wrap each in double quotes
# TODO: Display `...` behind patch-stat if the patch touched more files
# TODO: Use `-O <file>` for 'patch' command with `-- <file>` argument, so that
#       the passed file is ontop although the full patch is shown
# TODO: Support -L flag as well (add `-s` for list and `-- <file>` & maybe `-W`
#       for preview)
fzf_preview[files_only]="$fzf_preview[patch] ${(@)${@:${@[(ei)--]}}/(#m)*/\"$MATCH\"}"

# Use git's pager in the preview window (and with it any special highlighting
# tool, such as diff-so-fancy)
local pager
pager="$(git config --get --default="" core.pager)"
fzf_preview[patch]+="${pager:+ | }$pager; }"
fzf_preview[files_only]+="${pager:+ | }$pager; }"

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 ]] && (( $+commands[pbcopy] )); then
	fzf_copy_command+=" | pbcopy"
elif (( $+commands[xclip] )); then
	fzf_copy_command+=" | xclip -selection c"
fi

local -A binds=(
	# scroll in preview window
	"ctrl-alt-j" "preview-down"
	"ctrl-alt-k" "preview-up"
	# Copy commit hash
	"ctrl-y" "execute@$fzf_copy_command@"
	# Open preview "fullscreen"
	# NOTE: `-+F` is there to negate a possible --quit-if-one-screen
	# TODO: This assumes less to be used in core.pager
	"enter" "execute@$fzf_preview[patch] | $pager -+F@"
	# Preview stats
	"ctrl-s" "preview($fzf_preview[stat])"
	# Preview patch
	"ctrl-p" "preview($fzf_preview[patch])"
	# Files only
	"ctrl-f" "preview($fzf_preview[files_only])"
)

# TODO: Make the --preview argument dependent of --stat flag (i.e.
#       fzf_preview[stat] in this case). It does not really make sense to pass
#       it to `git log` but can be an indicator for the preview function

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[files_only]"
	# 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. It should have at least 152 columns to fit a preview window on
# the right (12 hash, 50 subject, 80 patch, 10 git graph and fzf ui).
#
# ctrl-space should cycle through the preview-window positions, starting with
# hidden, then not the start position and than back the start position.
local -a tty_size
tty_size=(${=$(command stty size 2>/dev/null)})
if (( ! $? )) && (( $tty_size[2] > 152 )); then
	fzf_args+=(
		--preview-window=right
		--bind "ctrl-space:change-preview-window(hidden|bottom|right)"
	)
else
	fzf_args+=(
		--preview-window=down
		--bind "ctrl-space:change-preview-window(hidden|right|bottom)"
	)
fi

# Display the commits in the above format and pipe that into fzf if stdout is a
# terminal.
if [ -t 1 ]; then
	git log "$formatshort" "$dateshort" --color=always "$@" \
	| env LESS="$LESS${LESS:+ }-+F" fzf "${fzf_args[@]}"
else
	git log "$formatshort" "$dateshort" --color=always "$@"
fi
return 0