#!/usr/bin/env bash
#
# html_mail_send.sh - A sophisticated HTML email sender
# Sends HTML emails via SMTP with style
#

set -euo pipefail

# ═══════════════════════════════════════════════════════════════════════════════
# COLORS & STYLING
# ═══════════════════════════════════════════════════════════════════════════════

# Reset
RST='\033[0m'

# Regular Colors
BLK='\033[0;30m'   RED='\033[0;31m'   GRN='\033[0;32m'   YLW='\033[0;33m'
BLU='\033[0;34m'   MAG='\033[0;35m'   CYN='\033[0;36m'   WHT='\033[0;37m'

# Bold Colors
BBLK='\033[1;30m'  BRED='\033[1;31m'  BGRN='\033[1;32m'  BYLW='\033[1;33m'
BBLU='\033[1;34m'  BMAG='\033[1;35m'  BCYN='\033[1;36m'  BWHT='\033[1;37m'

# Background Colors
BGBLK='\033[40m'   BGRED='\033[41m'   BGGRN='\033[42m'   BGYLW='\033[43m'
BGBLU='\033[44m'   BGMAG='\033[45m'   BGCYN='\033[46m'   BGWHT='\033[47m'

# Special
DIM='\033[2m'      ITALIC='\033[3m'   ULINE='\033[4m'    BLINK='\033[5m'

# Gradient colors (256 color mode)
G1='\033[38;5;39m'    # Light blue
G2='\033[38;5;38m'    # Cyan
G3='\033[38;5;37m'    # Teal
G4='\033[38;5;36m'    # Sea green
G5='\033[38;5;35m'    # Green

# Accent colors
ACC1='\033[38;5;213m'  # Pink
ACC2='\033[38;5;207m'  # Hot pink
ACC3='\033[38;5;171m'  # Purple
ACC4='\033[38;5;135m'  # Violet

# ═══════════════════════════════════════════════════════════════════════════════
# UNICODE SYMBOLS
# ═══════════════════════════════════════════════════════════════════════════════

SYM_CHECK="✓"
SYM_CROSS="✗"
SYM_ARROW="→"
SYM_MAIL="✉"
SYM_LOCK="🔒"
SYM_SEND="📤"
SYM_DOT="●"
SYM_STAR="★"
SYM_BOLT="⚡"
SYM_INFO="ℹ"
SYM_WARN="⚠"

# Box drawing characters
BOX_TL="╭"  BOX_TR="╮"  BOX_BL="╰"  BOX_BR="╯"
BOX_H="─"   BOX_V="│"   BOX_HB="━"

# ═══════════════════════════════════════════════════════════════════════════════
# CONFIGURATION
# ═══════════════════════════════════════════════════════════════════════════════

VERSION="1.0.0"
SCRIPT_NAME="$(basename "$0")"

# Default values
SMTP_SERVER=""
SMTP_PORT="587"
SMTP_USER=""
SMTP_PASS=""
SMTP_TLS="yes"
FROM_EMAIL=""
FROM_NAME=""
TO_EMAIL=""
SUBJECT=""
HTML_FILE=""
VERBOSE=false
DRY_RUN=false

# ═══════════════════════════════════════════════════════════════════════════════
# HELPER FUNCTIONS
# ═══════════════════════════════════════════════════════════════════════════════

print_header() {
    local width=60
    echo ""
    echo -e "${G1}${BOX_TL}$(printf '%*s' $((width-2)) '' | tr ' ' "$BOX_H")${BOX_TR}${RST}"
    echo -e "${G2}${BOX_V}${RST}  ${BMAG}${SYM_MAIL}${RST}  ${BWHT}S E N D _ M A I L${RST}  ${ACC1}v${VERSION}${RST}$(printf '%*s' 23 '')${G2}${BOX_V}${RST}"
    echo -e "${G3}${BOX_V}${RST}     ${DIM}${ITALIC}Sophisticated HTML Email Sender${RST}$(printf '%*s' 18 '')${G3}${BOX_V}${RST}"
    echo -e "${G4}${BOX_BL}$(printf '%*s' $((width-2)) '' | tr ' ' "$BOX_H")${BOX_BR}${RST}"
    echo ""
}

print_section() {
    local title="$1"
    echo -e "\n${ACC3}${SYM_STAR}${RST} ${BCYN}${title}${RST}"
    echo -e "${DIM}$(printf '%*s' 50 '' | tr ' ' '─')${RST}"
}

print_success() {
    echo -e "${BGRN}${SYM_CHECK}${RST} ${GRN}$1${RST}"
}

print_error() {
    echo -e "${BRED}${SYM_CROSS}${RST} ${RED}$1${RST}" >&2
}

print_warning() {
    echo -e "${BYLW}${SYM_WARN}${RST} ${YLW}$1${RST}"
}

print_info() {
    echo -e "${BCYN}${SYM_INFO}${RST} ${CYN}$1${RST}"
}

print_step() {
    echo -e "  ${ACC1}${SYM_ARROW}${RST} ${WHT}$1${RST}"
}

print_value() {
    local label="$1"
    local value="$2"
    printf "  ${DIM}%-15s${RST} ${BWHT}%s${RST}\n" "$label:" "$value"
}

spinner() {
    local pid=$1
    local message="${2:-Processing}"
    local spinchars='⠋⠙⠹⠸⠼⠴⠦⠧⠇⠏'
    local i=0

    tput civis  # Hide cursor
    while kill -0 "$pid" 2>/dev/null; do
        printf "\r  ${ACC2}${spinchars:i++%${#spinchars}:1}${RST} ${WHT}%s...${RST}" "$message"
        sleep 0.1
    done
    tput cnorm  # Show cursor
    printf "\r%*s\r" 50 ""  # Clear line
}

progress_bar() {
    local current=$1
    local total=$2
    local width=30
    local percent=$((current * 100 / total))
    local filled=$((current * width / total))
    local empty=$((width - filled))

    local bar=""
    for ((i=0; i<filled; i++)); do
        if ((i < filled / 3)); then
            bar+="${G1}${SYM_DOT}${RST}"
        elif ((i < 2 * filled / 3)); then
            bar+="${G3}${SYM_DOT}${RST}"
        else
            bar+="${G5}${SYM_DOT}${RST}"
        fi
    done
    for ((i=0; i<empty; i++)); do
        bar+="${DIM}○${RST}"
    done

    printf "\r  [%s] ${BWHT}%3d%%${RST}" "$bar" "$percent"
}

# ═══════════════════════════════════════════════════════════════════════════════
# USAGE & HELP
# ═══════════════════════════════════════════════════════════════════════════════

show_usage() {
    print_header

    echo -e "${BWHT}USAGE${RST}"
    echo -e "  ${GRN}$SCRIPT_NAME${RST} ${CYN}[OPTIONS]${RST} ${YLW}-s SERVER -u USER -p PASS -f FROM -t TO -j SUBJECT -h FILE${RST}"
    echo ""

    echo -e "${BWHT}REQUIRED OPTIONS${RST}"
    echo -e "  ${BCYN}-s, --server${RST} ${DIM}SERVER${RST}    SMTP server hostname"
    echo -e "  ${BCYN}-u, --user${RST} ${DIM}USER${RST}        SMTP username"
    echo -e "  ${BCYN}-p, --pass${RST} ${DIM}PASS${RST}        SMTP password (or use SMTP_PASSWORD env var)"
    echo -e "  ${BCYN}-f, --from${RST} ${DIM}EMAIL${RST}       Sender email address"
    echo -e "  ${BCYN}-t, --to${RST} ${DIM}EMAIL${RST}         Recipient email address"
    echo -e "  ${BCYN}-j, --subject${RST} ${DIM}TEXT${RST}     Email subject line"
    echo -e "  ${BCYN}-h, --html${RST} ${DIM}FILE${RST}        Path to HTML file"
    echo ""

    echo -e "${BWHT}OPTIONAL${RST}"
    echo -e "  ${BCYN}-P, --port${RST} ${DIM}PORT${RST}        SMTP port (default: 587)"
    echo -e "  ${BCYN}-n, --name${RST} ${DIM}NAME${RST}        Sender display name"
    echo -e "  ${BCYN}    --no-tls${RST}            Disable TLS/STARTTLS"
    echo -e "  ${BCYN}    --ssl${RST}               Use SSL (port 465)"
    echo -e "  ${BCYN}-v, --verbose${RST}           Verbose output"
    echo -e "  ${BCYN}    --dry-run${RST}           Show what would be sent without sending"
    echo -e "  ${BCYN}    --help${RST}              Show this help message"
    echo -e "  ${BCYN}    --version${RST}           Show version"
    echo ""

    echo -e "${BWHT}EXAMPLES${RST}"
    echo -e "  ${DIM}# Basic usage${RST}"
    echo -e "  ${GRN}$SCRIPT_NAME${RST} -s smtp.gmail.com -u user@gmail.com -p 'app-password' \\"
    echo -e "      -f user@gmail.com -t recipient@example.com \\"
    echo -e "      -j 'Hello World' -h email.html"
    echo ""
    echo -e "  ${DIM}# Using environment variable for password${RST}"
    echo -e "  ${YLW}export SMTP_PASSWORD='your-password'${RST}"
    echo -e "  ${GRN}$SCRIPT_NAME${RST} -s smtp.example.com -u user -f sender@example.com \\"
    echo -e "      -t recipient@example.com -j 'Subject' -h template.html"
    echo ""
    echo -e "  ${DIM}# With sender name and custom port${RST}"
    echo -e "  ${GRN}$SCRIPT_NAME${RST} -s mail.example.com -P 465 --ssl \\"
    echo -e "      -u user -p pass -f sender@example.com -n 'John Doe' \\"
    echo -e "      -t recipient@example.com -j 'Important' -h message.html"
    echo ""

    echo -e "${BWHT}ENVIRONMENT VARIABLES${RST}"
    echo -e "  ${BCYN}SMTP_PASSWORD${RST}    SMTP password (alternative to -p flag)"
    echo ""

    echo -e "${DIM}─────────────────────────────────────────────────────${RST}"
    echo -e "${DIM}Requires: curl with SMTP support${RST}"
    echo ""
}

show_version() {
    echo -e "${BMAG}${SYM_MAIL}${RST} ${BWHT}html_mail_send.sh${RST} ${ACC1}v${VERSION}${RST}"
}

# ═══════════════════════════════════════════════════════════════════════════════
# VALIDATION
# ═══════════════════════════════════════════════════════════════════════════════

validate_email() {
    local email="$1"
    if [[ "$email" =~ ^[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,}$ ]]; then
        return 0
    fi
    return 1
}

validate_file() {
    local file="$1"
    if [[ -f "$file" && -r "$file" ]]; then
        return 0
    fi
    return 1
}

check_dependencies() {
    if ! command -v curl &>/dev/null; then
        print_error "curl is required but not installed"
        echo -e "  ${DIM}Install with: ${RST}${CYN}sudo apt install curl${RST}"
        exit 1
    fi

    # Check if curl has SMTP support
    if ! curl -V | grep -q 'smtp'; then
        print_warning "curl may not have SMTP support"
    fi
}

validate_inputs() {
    local errors=0

    print_section "Validating Configuration"

    # Check required fields
    if [[ -z "$SMTP_SERVER" ]]; then
        print_error "SMTP server is required (-s, --server)"
        ((errors++))
    else
        print_success "SMTP server: $SMTP_SERVER"
    fi

    if [[ -z "$SMTP_USER" ]]; then
        print_error "SMTP username is required (-u, --user)"
        ((errors++))
    else
        print_success "SMTP user: $SMTP_USER"
    fi

    if [[ -z "$SMTP_PASS" ]]; then
        # Try environment variable
        if [[ -n "${SMTP_PASSWORD:-}" ]]; then
            SMTP_PASS="$SMTP_PASSWORD"
            print_success "SMTP password: (from environment)"
        else
            print_error "SMTP password is required (-p, --pass or SMTP_PASSWORD env var)"
            ((errors++))
        fi
    else
        print_success "SMTP password: ********"
    fi

    if [[ -z "$FROM_EMAIL" ]]; then
        print_error "From email is required (-f, --from)"
        ((errors++))
    elif ! validate_email "$FROM_EMAIL"; then
        print_error "Invalid from email format: $FROM_EMAIL"
        ((errors++))
    else
        print_success "From: ${FROM_NAME:+$FROM_NAME <}$FROM_EMAIL${FROM_NAME:+>}"
    fi

    if [[ -z "$TO_EMAIL" ]]; then
        print_error "To email is required (-t, --to)"
        ((errors++))
    elif ! validate_email "$TO_EMAIL"; then
        print_error "Invalid to email format: $TO_EMAIL"
        ((errors++))
    else
        print_success "To: $TO_EMAIL"
    fi

    if [[ -z "$SUBJECT" ]]; then
        print_error "Subject is required (-j, --subject)"
        ((errors++))
    else
        print_success "Subject: $SUBJECT"
    fi

    if [[ -z "$HTML_FILE" ]]; then
        print_error "HTML file is required (-h, --html)"
        ((errors++))
    elif ! validate_file "$HTML_FILE"; then
        print_error "HTML file not found or not readable: $HTML_FILE"
        ((errors++))
    else
        local size
        size=$(stat -c%s "$HTML_FILE" 2>/dev/null || stat -f%z "$HTML_FILE" 2>/dev/null || echo "?")
        print_success "HTML file: $HTML_FILE (${size} bytes)"
    fi

    if ((errors > 0)); then
        echo ""
        print_error "Found $errors error(s). Please fix and try again."
        echo ""
        exit 1
    fi

    echo ""
    print_success "All validations passed!"
}

# ═══════════════════════════════════════════════════════════════════════════════
# EMAIL SENDING
# ═══════════════════════════════════════════════════════════════════════════════

generate_boundary() {
    echo "----=_Part_$(date +%s%N)_$(od -An -tx4 -N4 /dev/urandom | tr -d ' ')"
}

send_email() {
    print_section "Preparing Email"

    local boundary
    boundary=$(generate_boundary)

    # Build From header
    local from_header
    if [[ -n "$FROM_NAME" ]]; then
        from_header="$FROM_NAME <$FROM_EMAIL>"
    else
        from_header="$FROM_EMAIL"
    fi

    # Generate message ID
    local msg_id
    msg_id="<$(date +%s%N).$(od -An -tx4 -N4 /dev/urandom | tr -d ' ')@${SMTP_SERVER}>"

    # Current date in RFC 2822 format
    local date_header
    date_header=$(date -R)

    print_step "Building MIME message..."

    # Create temporary file for email content
    local tmp_email
    tmp_email=$(mktemp)
    # Store in global for cleanup trap
    _TMP_EMAIL="$tmp_email"
    trap 'rm -f "$_TMP_EMAIL"' EXIT

    # Build the email with proper CRLF line endings for SMTP
    {
        printf 'From: %s\r\n' "$from_header"
        printf 'To: %s\r\n' "$TO_EMAIL"
        printf 'Subject: %s\r\n' "$SUBJECT"
        printf 'Date: %s\r\n' "$date_header"
        printf 'Message-ID: %s\r\n' "$msg_id"
        printf 'MIME-Version: 1.0\r\n'
        printf 'Content-Type: multipart/alternative; boundary="%s"\r\n' "$boundary"
        printf 'X-Mailer: html_mail_send.sh/%s\r\n' "$VERSION"
        printf '\r\n'
        printf -- '--%s\r\n' "$boundary"
        printf 'Content-Type: text/plain; charset="UTF-8"\r\n'
        printf 'Content-Transfer-Encoding: 7bit\r\n'
        printf '\r\n'
        printf 'This email requires an HTML-capable email client.\r\n'
        printf '\r\n'
        printf -- '--%s\r\n' "$boundary"
        printf 'Content-Type: text/html; charset="UTF-8"\r\n'
        printf 'Content-Transfer-Encoding: base64\r\n'
        printf '\r\n'
        # Base64 encode with 76-char lines and convert LF to CRLF
        base64 -w 76 "$HTML_FILE" | sed 's/$/\r/'
        printf '\r\n'
        printf -- '--%s--\r\n' "$boundary"
    } > "$tmp_email"

    print_success "MIME message created"

    # Show summary
    print_section "Email Summary"
    print_value "From" "$from_header"
    print_value "To" "$TO_EMAIL"
    print_value "Subject" "$SUBJECT"
    print_value "SMTP Server" "${SMTP_SERVER}:${SMTP_PORT}"
    print_value "TLS/SSL" "$([[ "$SMTP_TLS" == "yes" ]] && echo "Enabled" || echo "Disabled")"

    if [[ "$DRY_RUN" == "true" ]]; then
        echo ""
        print_warning "DRY RUN - Email would be sent with the above settings"
        print_info "Email content saved to: $tmp_email"

        if [[ "$VERBOSE" == "true" ]]; then
            print_section "Email Content Preview"
            echo -e "${DIM}"
            head -50 "$tmp_email"
            echo -e "${RST}"
            echo -e "${DIM}[... truncated ...]${RST}"
        fi

        # Don't delete temp file in dry run
        trap - EXIT
        return 0
    fi

    print_section "Sending Email"

    # Build curl command
    local curl_opts=()
    curl_opts+=(--url "smtp://${SMTP_SERVER}:${SMTP_PORT}")
    curl_opts+=(--user "${SMTP_USER}:${SMTP_PASS}")
    curl_opts+=(--mail-from "$FROM_EMAIL")
    curl_opts+=(--mail-rcpt "$TO_EMAIL")
    curl_opts+=(--upload-file "$tmp_email")

    if [[ "$SMTP_TLS" == "yes" ]]; then
        curl_opts+=(--ssl-reqd)
    elif [[ "$SMTP_TLS" == "ssl" ]]; then
        curl_opts=(--url "smtps://${SMTP_SERVER}:${SMTP_PORT}" "${curl_opts[@]:1}")
    fi

    if [[ "$VERBOSE" == "true" ]]; then
        curl_opts+=(--verbose)
    else
        curl_opts+=(--silent --show-error)
    fi

    # Send the email
    echo -ne "  ${ACC2}⠋${RST} ${WHT}Connecting to SMTP server...${RST}"

    local start_time
    start_time=$(date +%s)

    if curl "${curl_opts[@]}" 2>&1; then
        local end_time
        end_time=$(date +%s)
        local duration=$((end_time - start_time))

        printf "\r%*s\r" 50 ""
        echo ""
        echo -e "  ${BGGRN}${BLK} ${SYM_CHECK} SUCCESS ${RST}"
        echo ""
        print_success "Email sent successfully!"
        print_info "Delivery time: ${duration}s"
        echo ""

        # Fun success animation
        echo -e "  ${G1}${SYM_SEND}${RST} ${SYM_ARROW} ${G3}${SYM_ARROW}${RST} ${G5}${SYM_ARROW}${RST} ${ACC1}${SYM_MAIL}${RST} ${DIM}→ ${TO_EMAIL}${RST}"
        echo ""
    else
        printf "\r%*s\r" 50 ""
        echo ""
        echo -e "  ${BGRED}${WHT} ${SYM_CROSS} FAILED ${RST}"
        echo ""
        print_error "Failed to send email"
        print_info "Try running with --verbose for more details"
        exit 1
    fi
}

# ═══════════════════════════════════════════════════════════════════════════════
# ARGUMENT PARSING
# ═══════════════════════════════════════════════════════════════════════════════

parse_args() {
    while [[ $# -gt 0 ]]; do
        case "$1" in
            -s|--server)
                SMTP_SERVER="$2"
                shift 2
                ;;
            -P|--port)
                SMTP_PORT="$2"
                shift 2
                ;;
            -u|--user)
                SMTP_USER="$2"
                shift 2
                ;;
            -p|--pass)
                SMTP_PASS="$2"
                shift 2
                ;;
            -f|--from)
                FROM_EMAIL="$2"
                shift 2
                ;;
            -n|--name)
                FROM_NAME="$2"
                shift 2
                ;;
            -t|--to)
                TO_EMAIL="$2"
                shift 2
                ;;
            -j|--subject)
                SUBJECT="$2"
                shift 2
                ;;
            -h|--html)
                HTML_FILE="$2"
                shift 2
                ;;
            --no-tls)
                SMTP_TLS="no"
                shift
                ;;
            --ssl)
                SMTP_TLS="ssl"
                SMTP_PORT="${SMTP_PORT:-465}"
                shift
                ;;
            -v|--verbose)
                VERBOSE=true
                shift
                ;;
            --dry-run)
                DRY_RUN=true
                shift
                ;;
            --help)
                show_usage
                exit 0
                ;;
            --version)
                show_version
                exit 0
                ;;
            -*)
                print_error "Unknown option: $1"
                echo -e "  Run ${CYN}$SCRIPT_NAME --help${RST} for usage"
                exit 1
                ;;
            *)
                print_error "Unexpected argument: $1"
                echo -e "  Run ${CYN}$SCRIPT_NAME --help${RST} for usage"
                exit 1
                ;;
        esac
    done
}

# ═══════════════════════════════════════════════════════════════════════════════
# INTERACTIVE MODE
# ═══════════════════════════════════════════════════════════════════════════════

prompt_input() {
    local prompt="$1"
    local var_name="$2"
    local default="${3:-}"
    local is_password="${4:-false}"

    local current_value="${!var_name}"

    if [[ -n "$default" ]]; then
        printf "  ${ACC1}${SYM_ARROW}${RST} ${WHT}%s${RST} ${DIM}[%s]${RST}: " "$prompt" "$default"
    else
        printf "  ${ACC1}${SYM_ARROW}${RST} ${WHT}%s${RST}: " "$prompt"
    fi

    local input
    if [[ "$is_password" == "true" ]]; then
        read -rs input
        echo ""
    else
        read -r input
    fi

    if [[ -z "$input" && -n "$default" ]]; then
        eval "$var_name='$default'"
    elif [[ -n "$input" ]]; then
        eval "$var_name='$input'"
    fi
}

interactive_mode() {
    print_header

    print_section "SMTP Configuration"
    prompt_input "SMTP Server" SMTP_SERVER
    prompt_input "SMTP Port" SMTP_PORT "587"
    prompt_input "SMTP Username" SMTP_USER

    if [[ -z "$SMTP_PASS" && -z "${SMTP_PASSWORD:-}" ]]; then
        prompt_input "SMTP Password" SMTP_PASS "" true
    else
        print_info "Using password from environment or argument"
    fi

    echo ""
    echo -e "  ${DIM}TLS/SSL Options:${RST}"
    echo -e "    ${CYN}1${RST}) STARTTLS (port 587) ${DIM}- recommended${RST}"
    echo -e "    ${CYN}2${RST}) SSL/TLS (port 465)"
    echo -e "    ${CYN}3${RST}) None (insecure)"
    printf "  ${ACC1}${SYM_ARROW}${RST} ${WHT}Select encryption${RST} ${DIM}[1]${RST}: "
    read -r tls_choice

    case "${tls_choice:-1}" in
        2)
            SMTP_TLS="ssl"
            SMTP_PORT="465"
            ;;
        3)
            SMTP_TLS="no"
            ;;
        *)
            SMTP_TLS="yes"
            ;;
    esac

    print_section "Email Details"
    prompt_input "From Email" FROM_EMAIL
    prompt_input "From Name (optional)" FROM_NAME
    prompt_input "To Email" TO_EMAIL
    prompt_input "Subject" SUBJECT
    prompt_input "HTML File Path" HTML_FILE

    echo ""
}

# ═══════════════════════════════════════════════════════════════════════════════
# MAIN
# ═══════════════════════════════════════════════════════════════════════════════

main() {
    # Parse command line arguments
    parse_args "$@"

    # If no arguments provided, run interactive mode
    if [[ -z "$SMTP_SERVER" && -z "$HTML_FILE" ]]; then
        interactive_mode
    else
        print_header
    fi

    # Check dependencies
    check_dependencies

    # Validate all inputs
    validate_inputs

    # Send the email
    send_email
}

# Run main function
main "$@"