package config

import (
	"fmt"
	"path"
	"regexp"
	"strings"
)

// SSHOptions are connection settings that can be set globally, per NetBox
// instance, and per rule. More specific layers override less specific ones.
type SSHOptions struct {
	// ProxyJump is passed as -J; "none" disables a jump host set by a broader layer.
	ProxyJump string `mapstructure:"proxy_jump"`
	// HostKeyChecking is strict, accept-new, or off. Empty keeps ssh's own setting.
	HostKeyChecking string `mapstructure:"host_key_checking"`
	// Target selects the ssh destination: ip (default), name, or hostname.
	Target string `mapstructure:"target"`
	// AddressFamily is any, inet, or inet6.
	AddressFamily string `mapstructure:"address_family"`
	// ExtraArgs are inserted verbatim before the destination.
	ExtraArgs []string `mapstructure:"extra_args"`
	// Options are passed as -o Key=Value.
	Options map[string]string `mapstructure:"options"`
}

// SSHRule applies SSH options to hosts that match every non-empty field.
type SSHRule struct {
	Match      SSHMatch `mapstructure:"match"`
	SSHOptions `mapstructure:",squash"`
}

// SSHMatch selects hosts by NetBox attributes available in the cache.
type SSHMatch struct {
	Tag      string `mapstructure:"tag"`
	Instance string `mapstructure:"instance"`
	Kind     string `mapstructure:"kind"`
	Name     string `mapstructure:"name"` // shell-style glob, e.g. "*.dmz.example.com"
}

// SSHHost identifies the resolved host that SSH options are computed for.
type SSHHost struct {
	Instance string
	Name     string // NetBox name without the instance prefix
	Kind     string
	Tags     []string
}

var sshOptionKey = regexp.MustCompile(`^[A-Za-z][A-Za-z0-9]*$`)

// ValidateSSH rejects values that would be passed to ssh in an unexpected form.
func (c *Config) ValidateSSH() error {
	if err := c.SSH.SSHOptions.validate("ssh"); err != nil {
		return err
	}
	for i, rule := range c.SSH.Rules {
		if err := rule.SSHOptions.validate(fmt.Sprintf("ssh.rules[%d]", i)); err != nil {
			return err
		}
		if rule.Match == (SSHMatch{}) {
			return fmt.Errorf("ssh.rules[%d]: match must set at least one of tag, instance, kind, name", i)
		}
		if _, err := path.Match(rule.Match.Name, ""); err != nil {
			return fmt.Errorf("ssh.rules[%d]: invalid name pattern %q", i, rule.Match.Name)
		}
	}
	if err := c.NetBox.SSH.validate("netbox.ssh"); err != nil {
		return err
	}
	for _, source := range c.NetBoxes {
		if err := source.SSH.validate("netboxes." + source.Name + ".ssh"); err != nil {
			return err
		}
	}
	return nil
}

func (o SSHOptions) validate(scope string) error {
	switch o.HostKeyChecking {
	case "", "strict", "accept-new", "off":
	default:
		return fmt.Errorf("%s.host_key_checking must be strict, accept-new, or off", scope)
	}
	switch o.Target {
	case "", "ip", "name", "hostname":
	default:
		return fmt.Errorf("%s.target must be ip, name, or hostname", scope)
	}
	switch o.AddressFamily {
	case "", "any", "inet", "inet6":
	default:
		return fmt.Errorf("%s.address_family must be any, inet, or inet6", scope)
	}
	if strings.HasPrefix(o.ProxyJump, "-") || strings.ContainsAny(o.ProxyJump, " \t\n") {
		return fmt.Errorf("%s.proxy_jump %q is not a valid jump host", scope, o.ProxyJump)
	}
	for key, value := range o.Options {
		if !sshOptionKey.MatchString(key) || strings.ContainsAny(value, "\n\r") {
			return fmt.Errorf("%s.options: invalid option %q", scope, key)
		}
	}
	return nil
}

// SSHOptionsFor merges global, instance, and matching rule options for host.
func (c *Config) SSHOptionsFor(host SSHHost) SSHOptions {
	merged := c.SSH.SSHOptions.merge(SSHOptions{})
	if host.Instance == "" {
		merged = merged.merge(c.NetBox.SSH)
	}
	for _, source := range c.NetBoxes {
		if strings.EqualFold(source.Name, host.Instance) {
			merged = merged.merge(source.SSH)
		}
	}
	for _, rule := range c.SSH.Rules {
		if rule.Match.matches(host) {
			merged = merged.merge(rule.SSHOptions)
		}
	}
	return merged
}

// merge returns o overridden by the non-empty fields of override.
// Extra arguments accumulate; options override per key.
func (o SSHOptions) merge(override SSHOptions) SSHOptions {
	out := o
	out.ExtraArgs = append(append([]string(nil), o.ExtraArgs...), override.ExtraArgs...)
	out.Options = make(map[string]string, len(o.Options)+len(override.Options))
	for key, value := range o.Options {
		out.Options[strings.ToLower(key)] = value
	}
	for key, value := range override.Options {
		out.Options[strings.ToLower(key)] = value
	}
	if override.ProxyJump != "" {
		out.ProxyJump = override.ProxyJump
	}
	if override.HostKeyChecking != "" {
		out.HostKeyChecking = override.HostKeyChecking
	}
	if override.Target != "" {
		out.Target = override.Target
	}
	if override.AddressFamily != "" {
		out.AddressFamily = override.AddressFamily
	}
	return out
}

func (m SSHMatch) matches(host SSHHost) bool {
	if m.Instance != "" && !strings.EqualFold(m.Instance, host.Instance) {
		return false
	}
	if m.Kind != "" && !strings.EqualFold(m.Kind, host.Kind) {
		return false
	}
	if m.Name != "" {
		if ok, _ := path.Match(strings.ToLower(m.Name), strings.ToLower(host.Name)); !ok {
			return false
		}
	}
	if m.Tag != "" {
		found := false
		for _, tag := range host.Tags {
			if strings.EqualFold(tag, m.Tag) || strings.EqualFold(tagSlug(tag), m.Tag) {
				found = true
				break
			}
		}
		if !found {
			return false
		}
	}
	return true
}

// tagSlug approximates NetBox's slug so rules may use either the tag name or slug.
func tagSlug(name string) string {
	return strings.Join(strings.Fields(strings.ToLower(name)), "-")
}