#!/bin/sh

# configure automatically sets up a wrapper at .git/hooks/pre-commit
# which calls this script (if it exists).

set -e

dev/tools/check-overlays.sh

# Can we check and fix formatting?
# NB: we will ignore errors from ocamlformat as it fails when
# encountering OCaml syntax errors
ocamlformat=$(command -v ocamlformat || echo true)
if [ "$ocamlformat" = true ]
then
    1>&2 echo "Warning: ocamlformat is not in path. Cannot check formatting."
fi

# Verify that the version of ocamlformat matches the one in .ocamlformat
# The following command will print an error message if that's not the case
# (and will print nothing if the versions match)
if ! echo "let () = ()" | "$ocamlformat" --impl - > /dev/null
then
    1>&2 echo "Warning: Cannot check formatting."
    ocamlformat=true
fi

1>&2 echo "Auto fixing whitespace and formatting issues..."

# We fix whitespace in the index and in the working tree
# separately to preserve non-added changes.
index=$(mktemp "git-fix-ws-index.XXXXXX")
fixed_index=$(mktemp "git-fix-ws-index-fixed.XXXXXX")
tree=$(mktemp "git-fix-ws-tree.XXXXXX")
1>&2 echo "Patches are saved in '$index', '$fixed_index' and '$tree'."
1>&2 echo "If an error destroys your changes you can recover using them."
1>&2 echo "(The files are cleaned up on success.)"
1>&2 echo #newline

git diff-index -p --cached HEAD > "$index"
git diff-index -p HEAD > "$tree"

# reset work tree and index
# NB: untracked files which were not added are untouched
if [ -s "$index" ]; then git apply --whitespace=nowarn --cached -R "$index"; fi
if [ -s "$tree" ]; then git apply --whitespace=nowarn -R "$tree"; fi

# Fix index
# For end of file newlines we must go through the worktree
if [ -s "$index" ]; then
    1>&2 echo "Fixing staged changes..."
    git apply --cached --whitespace=fix "$index"
    git apply --whitespace=fix "$index" 2>/dev/null # no need to repeat yourself
    git diff --cached --name-only -z | xargs -0 dev/tools/check-eof-newline.sh --fix
    { git diff --cached --name-only -z | grep -E '.*\.mli?$' -z | xargs -0 "$ocamlformat" -i || true; } 2> /dev/null
    git add -u
    1>&2 echo #newline
fi

# reset work tree
git diff-index -p --cached HEAD > "$fixed_index"
# If all changes were bad whitespace changes the patch is empty
# making git fail. Don't fail now: we fix the worktree first.
if [ -s "$fixed_index" ]; then git apply --whitespace=nowarn -R "$fixed_index"; fi

# Fix worktree
if [ -s "$tree" ]; then
    1>&2 echo "Fixing unstaged changes..."
    git apply --whitespace=fix "$tree"
    git diff --name-only -z | xargs -0 dev/tools/check-eof-newline.sh --fix
    { git diff --name-only -z | grep -E '.*\.mli?$' -z | xargs -0 "$ocamlformat" -i || true; } 2> /dev/null
    1>&2 echo #newline
fi

if [ -s "$index" ] && ! [ -s "$fixed_index" ]; then
    1>&2 echo "Fixing whitespace and formatting issues cancelled all changes."
    exit 1
fi

# Check that we did fix whitespace
if ! git diff-index --check --cached HEAD; then
    1>&2 echo "Auto-fixing whitespace failed: errors remain."
    1>&2 echo "This may fix itself if you try again."
    1>&2 echo "(Consider whether the number of errors decreases after each run.)"
    exit 1
fi
1>&2 echo "Whitespace and formatting pass complete."

# clean up temporary files
rm "$index" "$tree" "$fixed_index"