#!/usr/bin/env bash
# Validate Go files after Edit/Write/MultiEdit.
# PostToolUse hook: receives tool-call JSON on stdin.
#
# On success: exit 0 silent.
# On failure: emit JSON with hookSpecificOutput.additionalContext so Claude
# sees a structured error in its context, THEN exit 2 to block the tool
# pipeline. stderr still echoes the error for terminal visibility.
#
# Phase 1: gofmt — formatting must be clean.
# Phase 2: go vet — compile + suspicious-construct check on the file's package,
#          run only when the file sits inside a module (go.mod found). go vet
#          type-checks, so it surfaces compile and syntax errors too.
#
# Tests deliberately stop here: `go test` on the edited package can pull in slow
# or integration-tagged tests that shouldn't fire on every keystroke. Run them
# explicitly via `make coverage` / `go test`.

set -u

# Emit a JSON failure payload and exit 2. Arguments:
#   $1 — short failure type (e.g. "GO VET FAILED")
#   $2 — file path
#   $3 — tool output (error body)
fail_json() {
    local ctx
    ctx="$(printf '%s: %s\n\n%s\n\nFix before proceeding.' "$1" "$2" "$3" \
        | jq -Rs .)"
    cat <<EOF
{"hookSpecificOutput": {"hookEventName": "PostToolUse", "additionalContext": $ctx}}
EOF
    printf '%s: %s\n%s\n' "$1" "$2" "$3" >&2
    exit 2
}

f="$(jq -r '.tool_input.file_path // .tool_response.filePath // empty')"
[ -z "$f" ] && exit 0
[ "${f##*.}" = "go" ] || exit 0
[ -f "$f" ] || exit 0

# No toolchain on this machine — nothing to validate, don't block the edit.
command -v gofmt >/dev/null 2>&1 || exit 0

# --- Phase 1: formatting ---
# gofmt -l prints the path when the file isn't gofmt-clean (and stays silent on
# a parse error — go vet catches those in Phase 2). Show the diff so the fix is
# obvious.
if [ -n "$(gofmt -l "$f" 2>/dev/null)" ]; then
    fail_json "GOFMT: file is not gofmt-clean" "$f" "$(gofmt -d "$f" 2>&1)"
fi

# --- Phase 2: vet (needs module context) ---
command -v go >/dev/null 2>&1 || exit 0
dir="$(dirname "$f")"
gomod="$(cd "$dir" && go env GOMOD 2>/dev/null)"
if [ -n "$gomod" ] && [ "$gomod" != "/dev/null" ]; then
    if ! out="$(cd "$dir" && go vet . 2>&1)"; then
        fail_json "GO VET FAILED" "$f" "$out"
    fi
fi

exit 0