#!/usr/bin/env bash
#
# Summary: Activate virtual environment
#
# Usage: pyenv link-venv [--dry] [--quiet] <virtualenv> [<name>]
#
# Link a virtual python environment to pyenvs version directory
# so that the venv can be used like one created with *pyenv-virtualenv*.
#
# <virtualenv> should be a path to a virtual python environments location.
# <name> should be string used as a version name it may not be present
#        in the pyenv version directory yet.
#        If not specified a matching name is guessed from pyvenv.cfg
#        or directory name of the venv.
set -e
[ -n "$PYENV_DEBUG" ] && set -x

# functions

if ! {
    enable -f "${BASH_SOURCE%/*}"/../../../libexec/pyenv-realpath.dylib realpath ||
        type realpath # realpath available?
} >/dev/null 2>&1; then
    # realpath requires GNU coreutils to be installed. That's why its bundled with pyenv
    echo realpath not available >&2

    # work-around when realpath is unavailable
    realpath() {
        echo "$(cd "$1" && pwd)"
    }
fi

array_doesnt_contain() {
    local array="$1[@]"
    local seeking=$2
    local in=0
    for element in "${!array}"; do
        if [[ $element == "$seeking" ]]; then
            in=1
            break
        fi
    done
    return $in
}

COMMON_VENV_NAMES=('venv' 'env' '.venv' '.env' 'ENV' 'VENV')
guess_name() {
    local venv_dir=$1
    local name

    # guess venv name from pyvenv.cfg
    local pyvenv_cfg_path=$venv_dir/pyvenv.cfg
    if [ -f "$pyvenv_cfg_path" ]; then
        # if `prompt` key wasn't found the var remains empty
        name=$(cut -b 1-1024 "$pyvenv_cfg_path" | sed -n '/^ *prompt *= */s///p')
    fi

    # guess venv name from name of venv directory
    local venv_dir_name=${venv_dir##*/}
    if [ -z "$name" ] && array_doesnt_contain COMMON_VENV_NAMES "$venv_dir_name"; then
        name=$venv_dir_name
    fi

    # guess venv name from name of the parent directory of the venv directory
    local venv_dir_parent=${venv_dir%/*}
    local venv_dir_parent_name=${venv_dir_parent##*/}
    if [ -z "$name" ]; then
        name=$venv_dir_parent_name
    fi

    echo "$name"
}

# process args
POSARGS=()
# Provide pyenv completions
if [ "$1" = "--complete" ]; then
    echo --dry
    echo --quiet
    exit
fi

for arg in "$@"; do
    case $arg in
    --dry)
        dry=true # any value
        ;;
    --quiet)
        quiet=true # any value
        ;;
    -*)
        pyenv-help --usage link-version >&2
        exit 1
        ;;
    *)
        POSARGS+=("$arg")
        ;;
    esac
done

if [ ! ${#POSARGS[@]} -le 2 ] || [ ! ${#POSARGS[@]} -ge 1 ]; then
    pyenv-help --usage link-version >&2
    exit 1
fi

venv_dir=${POSARGS[0]%/}
venv_name=${POSARGS[1]}

# Check venv exists
if [ ! -d "$venv_dir" ]; then
    echo "The virtual env you specified doesn't exist"
    exit 2
fi

# make venv dir absolute
venv_dir=$(realpath "$venv_dir")

# determine venv name
if [ -z "$venv_name" ]; then
    venv_name=$(guess_name "$venv_dir")
fi

# check whether version exists already
if pyenv-prefix "$venv_name"; then
    echo Version "$venv_name" already exists >&2
    exit 3
fi

# construct location to link to
pyenv_prefix_path="$PYENV_ROOT/versions/$venv_name"

# link to pyenv version directory
if [ -z "$dry" ]; then
    ln --symbolic "$venv_dir" "$pyenv_prefix_path"
fi

# output
[ -z "$quiet" ] && echo Linked new version named "$venv_name" || true