#!/bin/bash
# parse_params.sh - Shell library for parameter file parsing
#
# Description:
#   Provides reusable functions for parsing key=value parameter files,
#   validating required parameters, and generating parameter sweep cases.
#   This library is sourced by simulation scripts to handle configuration.
#
# Functions:
#   parse_param_file <file>     - Parse file, export as PARAM_* env vars
#   get_param <key> [default]   - Get parameter value with optional default
#   validate_required_params    - Check required parameters are set
#   print_params                - Debug: print all loaded parameters
#
# Usage:
#   source src-local/parse_params.sh
#   parse_param_file "config.params"
#   Oh=\$(get_param "Oh" "0.01")
#
# Dependencies:
#   - bash 4.0+ (for associative arrays and \${!var} syntax)
#   - Standard POSIX utilities (sed, xargs, mktemp)
#
# Author: Vatsal Sanjay
# Organization: CoMPhy Lab, Durham University

# Parse a parameter file and export all parameters as environment variables
# Usage: parse_param_file <file>
parse_param_file() {
    local param_file=\$1

    if [ ! -f "\$param_file" ]; then
        echo "ERROR: Parameter file \$param_file not found" >&2
        return 1
    fi

    # Read parameters (skip comments and empty lines)
    while IFS='=' read -r key value || [ -n "\$key" ]; do
        # Skip comments and empty lines
        [[ "\$key" =~ ^[[:space:]]*# ]] && continue
        [[ -z "\$key" ]] && continue

        # Remove inline comments and whitespace
        value=\$(echo "\$value" | sed 's/#.*//' | xargs)
        key=\$(echo "\$key" | xargs)

        # Skip if key or value is empty
        [ -z "\$key" ] && continue
        [ -z "\$value" ] && continue

        # Export as environment variable with PARAM_ prefix
        export "PARAM_\${key}=\${value}"
    done < "\$param_file"

    return 0
}

# Get a parameter value with optional default
# Usage: get_param <key> [default]
get_param() {
    local key=\$1
    local default=\${2:-}
    local var_name="PARAM_\${key}"
    echo "\${!var_name:-\$default}"
}

# Validate that required variables are set in parameter file
# Usage: validate_required_params <param1> <param2> ...
validate_required_params() {
    local missing=0

    for param in "\$@"; do
        local var_name="PARAM_\${param}"
        if [ -z "\${!var_name}" ]; then
            echo "ERROR: Required parameter '\$param' not found" >&2
            missing=1
        fi
    done

    return \$missing
}

# Print all loaded parameters (for debugging)
print_params() {
    echo "Loaded parameters:"
    env | grep "^PARAM_" | sort | while IFS='=' read -r key value; do
        key="\${key#PARAM_}"
        echo "  \$key = \$value"
    done
}

# Validate a restart file exists, is non-empty, and is readable
# Usage: validate_restart_file [file_path]
# Returns 0 if valid, 1 if invalid
validate_restart_file() {
    local restart_file="\${1:-restart}"

    if [ ! -f "\$restart_file" ]; then
        echo "ERROR: Restart file not found: \$restart_file" >&2
        return 1
    fi

    if [ ! -s "\$restart_file" ]; then
        echo "ERROR: Restart file is empty: \$restart_file" >&2
        return 1
    fi

    if [ ! -r "\$restart_file" ]; then
        echo "ERROR: Restart file not readable: \$restart_file" >&2
        return 1
    fi

    return 0
}