dante-ghci

#!/usr/bin/env bash

CURDIR="$PWD"

findconfig() {
    # via https://unix.stackexchange.com/questions/293393/find-a-specific-file-in-the-nearest-ancestor-of-the-current-working-directory
    # from: https://www.npmjs.com/package/find-config#algorithm
    # 1. If X/file.ext exists and is a regular file, return it. STOP
    # 2. If X has a parent directory, change X to parent. GO TO 1
    # 3. Return NULL.
    if [ -f "$1" ]; then
        printf '%s\n' "${PWD%/}/$1"
    elif [ "$PWD" = / ]; then
        false
    else
        # a subshell so that we don't affect the caller's $PWD
        (cd .. && findconfig "$1")
    fi
}

if [ "$1" != "--really" ]; then
    if (which direnv && direnv exec . true) 2>&1 >/dev/null && ROOT="${DIRENV_DIR:1}" && [ -n "$ROOT" ]; then
        echo wrapping using direnv
        exec direnv exec . "$0" --really "$@"
    elif which nix-shell 2>&1 >/dev/null; then

        NIX_SHELL="$(findconfig shell.nix)"
        NIX_DEFAULT="$(findconfig default.nix)"
        USE_SHELL_NIX=false

        if [ -n "$NIX_SHELL" -a -n "$NIX_DEFAULT" ]; then
            # choose the longer path
            if [ ${#NIX_SHELL} -gt ${#NIX_DEFAULT} ]; then
                USE_SHELL_NIX=true
            fi
        else
            if [ -n "$NIX_SHELL" ]; then
                USE_SHELL_NIX=true
            fi
        fi

        if $USE_SHELL_NIX; then
            echo wrapping using nix-shell "$NIX_SHELL"
            export ROOT="$(dirname "$NIX_SHELL")"
            exec nix-shell "$NIX_SHELL" --run "$0 --really $@"
        else
            echo wrapping using nix-shell -A env "$NIX_DEFAULT"
            export ROOT="$(dirname "$NIX_DEFAULT")"
            exec nix-shell "$NIX_DEFAULT" -A env --run "$0 --really $@"
        fi
    fi

fi

shift
OUTDIR="/tmp/dante/$(echo ${ROOT} | md5sum | cut -d' ' -f1)"
echo "ROOT=$ROOT"
echo "OUTDIR=$OUTDIR"
echo "USE_CABAL=$USE_CABAL"

if [ "$USE_CABAL" ]; then
    echo using cabal
    cabal new-repl --builddir="$OUTDIR" "$@"
else
    echo using ghci
    mkdir -p "$OUTDIR"
    GHCI_SCRIPT="${OUTDIR}/.ghci"
    echo ":cd ${ROOT}" > "$GHCI_SCRIPT"
    shift
    ghci -O0 \
         -ghci-script "$GHCI_SCRIPT" \
	       -ghci-script "${ROOT}/.ghci" \
	       -outputdir="${OUTDIR}" \
         -Wall \
         "$@"
fi