package config

import (
	"fmt"
	"regexp"
	"sort"
	"strings"
)

// MultiConfig controls netssh multi.
type MultiConfig struct {
	// Multiplexer is auto, tmux, or zellij; empty means auto.
	Multiplexer string `mapstructure:"multiplexer"`
	// PanesPerWindow splits larger host lists into more windows or tabs; 0 = 9.
	PanesPerWindow int `mapstructure:"panes_per_window"`
	// SyncKey and SoloKey are tmux prefix keys for broadcast to all panes and
	// for excluding the current pane; empty = default (S, e), "none" = off.
	SyncKey string `mapstructure:"sync_key"`
	SoloKey string `mapstructure:"solo_key"`
}

// Default tmux keys: unbound in a stock tmux (E would be "spread evenly").
const (
	DefaultSyncKey = "S"
	DefaultSoloKey = "e"
)

// Keys returns the tmux keys to bind; "" for a disabled one.
func (m MultiConfig) Keys() (sync, solo string) {
	pick := func(key, fallback string) string {
		switch key {
		case "":
			return fallback
		case "none":
			return ""
		}
		return key
	}
	return pick(m.SyncKey, DefaultSyncKey), pick(m.SoloKey, DefaultSoloKey)
}

var tmuxKey = regexp.MustCompile(`^([CMS]-)*([A-Za-z0-9]|F[0-9]{1,2}|[-_=+!@#$%^&*,./?<>\[\]]|Tab|Space|Enter|BSpace|Up|Down|Left|Right|Home|End|PPage|NPage)$`)

// DefaultPanesPerWindow keeps panes readable on a normal screen (3×3).
const DefaultPanesPerWindow = 9

// ValidateMulti checks groups and the multi settings.
func (c *Config) ValidateMulti() error {
	switch c.Multi.Multiplexer {
	case "", "auto", "tmux", "zellij":
	default:
		return fmt.Errorf("multi.multiplexer must be auto, tmux, or zellij")
	}
	if c.Multi.PanesPerWindow < 0 || c.Multi.PanesPerWindow > 64 {
		return fmt.Errorf("multi.panes_per_window must be between 1 and 64")
	}
	for name, key := range map[string]string{"sync_key": c.Multi.SyncKey, "solo_key": c.Multi.SoloKey} {
		if key != "" && key != "none" && !tmuxKey.MatchString(key) {
			return fmt.Errorf("multi.%s %q is not a tmux key (e.g. S, e, C-s, F5) or none", name, key)
		}
	}
	if sync, solo := c.Multi.Keys(); sync != "" && sync == solo {
		return fmt.Errorf("multi.sync_key and multi.solo_key must differ")
	}
	names := make([]string, 0, len(c.Groups))
	for name := range c.Groups {
		names = append(names, name)
	}
	sort.Strings(names)
	for _, name := range names {
		if !instanceName.MatchString(name) {
			return fmt.Errorf("groups: name %q must contain only letters, digits, underscores, or hyphens", name)
		}
		if len(c.Groups[name]) == 0 {
			return fmt.Errorf("groups.%s: needs at least one host or selector", name)
		}
		for _, selector := range c.Groups[name] {
			if strings.TrimSpace(selector) == "" || strings.ContainsAny(selector, " \t\n") || strings.HasPrefix(selector, "-") {
				return fmt.Errorf("groups.%s: invalid entry %q", name, selector)
			}
		}
	}
	return nil
}

// PanesPerWindowOrDefault returns the configured value or the default.
func (m MultiConfig) PanesPerWindowOrDefault() int {
	if m.PanesPerWindow > 0 {
		return m.PanesPerWindow
	}
	return DefaultPanesPerWindow
}