type Option interface {
    apply(*options)
}

package db

import "go.uber.org/zap"

// options holds all configuration for opening a connection.
type options struct {
    cache  bool
    logger *zap.Logger
}

// Option configures how we open the connection.
type Option interface {
    apply(*options)
}

// cacheOption implements Option for cache setting (simple type alias).
type cacheOption bool

func (c cacheOption) apply(opts *options) {
    opts.cache = bool(c)
}

// WithCache enables or disables caching.
func WithCache(c bool) Option {
    return cacheOption(c)
}

// loggerOption implements Option for logger setting (struct for pointers).
type loggerOption struct {
    Log *zap.Logger
}

func (l loggerOption) apply(opts *options) {
    opts.logger = l.Log
}

// WithLogger sets the logger for the connection.
func WithLogger(log *zap.Logger) Option {
    return loggerOption{Log: log}
}

// Open creates a connection.
func Open(addr string, opts ...Option) (*Connection, error) {
    // Start with defaults
    options := options{
        cache:  defaultCache,
        logger: zap.NewNop(),
    }

    // Apply all provided options
    for _, o := range opts {
        o.apply(&options)
    }

    // Use options.cache and options.logger...
    return &Connection{}, nil
}

// Caller must always provide all parameters, even defaults
db.Open(addr, db.DefaultCache, zap.NewNop())
db.Open(addr, db.DefaultCache, log)
db.Open(addr, false /* cache */, zap.NewNop())
db.Open(addr, false /* cache */, log)

// Only provide options when needed
db.Open(addr)
db.Open(addr, db.WithLogger(log))
db.Open(addr, db.WithCache(false))
db.Open(
    addr,
    db.WithCache(false),
    db.WithLogger(log),
)

// Closure approach (not recommended)
type Option func(*options)

func WithCache(c bool) Option {
    return func(o *options) { o.cache = c }
}

// 1. Unexported options struct with defaults
type options struct {
    field1 Type1
    field2 Type2
}

// 2. Exported Option interface, unexported method
type Option interface {
    apply(*options)
}

// 3. Option type + apply + With* constructor
type field1Option Type1

func (o field1Option) apply(opts *options) { opts.field1 = Type1(o) }
func WithField1(v Type1) Option            { return field1Option(v) }

// 4. Constructor applies options over defaults
func New(required string, opts ...Option) (*Thing, error) {
    o := options{field1: defaultField1, field2: defaultField2}
    for _, opt := range opts {
        opt.apply(&o)
    }
    // ...
}