#!/usr/bin/env bash

#
# jq_reformat - Reformat JSON files in-place using jq
#
# Usage: jq_reformat FILE [FILE...]
#
# This script reformats JSON files in-place by running them through jq.
# It preserves the original files by using atomic temporary file replacement,
# ensuring data safety even if the process is interrupted.
#
# Examples:
#   jq_reformat config.json
#   jq_reformat *.json
#   jq_reformat data/*.json settings.json
#

set -euo pipefail

#
# Show usage information
#
usage() {
    cat <<EOF
Usage: ,jq_reformat FILE [FILE...]

Reformat JSON files in-place using jq.

This script reformats JSON files by running them through jq's parser,
which produces consistently formatted, valid JSON. Files are updated
atomically using temporary files to prevent data loss.

Arguments:
  FILE    One or more JSON files to reformat

Options:
  -h, --help    Show this help message

Examples:
  ,jq_reformat config.json
  ,jq_reformat *.json
  ,jq_reformat data/*.json settings.json

Exit codes:
  0    Success - all files reformatted
  1    Error - invalid arguments, missing files, or jq errors
EOF
}

#
# Reformat a single JSON file in-place
#
# Arguments:
#   $1 - Path to the JSON file to reformat
#
# Returns:
#   0 on success, 1 on error
#
reformat_file() {
    local file="$1"
    local temp_file

    # Validate that the file exists and is readable
    if [[ ! -f "$file" ]]; then
        echo "Error: File not found: $file" >&2
        return 1
    fi

    if [[ ! -r "$file" ]]; then
        echo "Error: File not readable: $file" >&2
        return 1
    fi

    # Create a secure temporary file in the same directory as the target
    # This ensures we're on the same filesystem for atomic mv operation
    temp_file=$(mktemp "${file}.XXXXXX") || {
        echo "Error: Failed to create temporary file for: $file" >&2
        return 1
    }

    # Set up cleanup trap to remove temp file on error
    # shellcheck disable=SC2064
    trap "rm -f '$temp_file'" EXIT ERR

    # Run jq to reformat the JSON
    # - Read from the original file
    # - Write to temp file
    # - If successful, atomically replace the original
    if jq . <"$file" >"$temp_file" 2>/dev/null; then
        # Preserve original file permissions
        chmod --reference="$file" "$temp_file" 2>/dev/null || true

        # Atomically replace the original file
        mv "$temp_file" "$file"

        # Clear the trap since we succeeded
        trap - EXIT ERR
        return 0
    else
        # jq failed - the file is likely not valid JSON
        echo "Error: Failed to parse JSON in: $file" >&2
        rm -f "$temp_file"
        trap - EXIT ERR
        return 1
    fi
}

#
# Main script logic
#
main() {
    # Handle help flag
    if [[ $# -eq 0 ]] || [[ "$1" == "-h" ]] || [[ "$1" == "--help" ]]; then
        usage
        [[ $# -eq 0 ]] && return 1
        return 0
    fi

    local exit_code=0
    local file

    # Process each file argument
    # Using "$@" properly handles filenames with spaces and special characters
    for file in "$@"; do
        if ! reformat_file "$file"; then
            exit_code=1
            # Continue processing other files even if one fails
        fi
    done

    return "$exit_code"
}

# Run main function with all arguments
main "$@"