package main

import (
	"bytes"
	"errors"
	"fmt"
	"github.com/goccy/go-yaml"
	"net"
	"os"
	"slices"
)

var PREDEFINED_APPS = []string{"apiserver"}

func validateCIDR(cidr string) error {
	_, _, err := net.ParseCIDR(cidr)
	return err
}

type CIDR string

// UnmarshalYAML implements the yaml.Unmarshaler interface
func (c *CIDR) UnmarshalYAML(value []byte) error {
	// Get the string value from the node
	var s string
	if err := yaml.Unmarshal(value, &s); err != nil {
		return err
	}
	if err := validateCIDR(s); err != nil {
		return err
	}
	*c = CIDR(s)
	return nil
}

// MarshalYAML implements the yaml.Marshaler interface
func (c CIDR) MarshalYAML() ([]byte, error) {
	// Do any custom processing here before marshalling
	return []byte(string(c)), nil
}

type Port struct {
	Port     string `yaml:"port"`
	Protocol string `yaml:"protocol"`
}

// Network represents each network entry in the YAML
type Network struct {
	Name   string `yaml:"name"`
	CIDR   CIDR   `yaml:"cidr"`
	Except []CIDR `yaml:"except,omitempty"`
	Ports  []Port `yaml:"ports,omitempty"`
}

type Application struct {
	Name        string            `yaml:"name"`
	Ports       []Port            `yaml:"ports,omitempty"`
	MatchLabels map[string]string `yaml:"matchLabels"`
	Namespace   string            `yaml:"-"`
}

type Namespace struct {
	Name         string         `yaml:"name"`
	Open         bool           `yaml:"open"`
	Capabilities []string       `yaml:"capabilities"`
	Applications []*Application `yaml:"applications"`
}

type Communication struct {
	From  []string `yaml:"from"`
	To    []string `yaml:"to"`
	Ports []string `yaml:"ports"`
}

// Config represents the top-level YAML structure
type Config struct {
	Networks       []*Network       `yaml:"networks,omitempty"`
	Namespaces     []*Namespace     `yaml:"namespaces,omitempty"`
	Communications []*Communication `yaml:"communications,omitempty"`
}

func (c Config) Validate() error {

	errs := make([]error, 0)

	// namesapaces must be unique
	ns := make(map[string]bool)
	for _, namespace := range c.Namespaces {
		if ns[namespace.Name] {
			errs = append(errs, fmt.Errorf("Duplicate namespace name %s", namespace.Name))
		}
		ns[namespace.Name] = true
	}

	// network names mus tbe unique
	networks := make(map[string]bool)
	for _, network := range c.Networks {
		if networks[network.Name] {
			errs = append(errs, fmt.Errorf("Duplicate network name %s", network.Name))
		}
		networks[network.Name] = true
	}

	// application names must be unique and may not conflict with predefined applications
	apps := map[string]bool{
		"apiserver": true,
	}
	// application names may also not conflict with network names.
	for _, network := range c.Networks {
		apps[network.Name] = true
	}

	for _, namespace := range c.Namespaces {
		for _, app := range namespace.Applications {
			if apps[app.Name] {
				errs = append(errs, fmt.Errorf("Duplicate application %s (%s)", app.Name, namespace.Name))
			}
			apps[app.Name] = true
		}
	}

	// applications mentioned in a communication must exist
	for _, communication := range c.Communications {
		for _, from := range communication.From {
			if !apps[from] {
				errs = append(errs, fmt.Errorf("Application does not exist: %s referenced in a communication (%+v)", from, communication))
			}
		}
		for _, to := range communication.To {
			if !apps[to] {
				errs = append(errs, fmt.Errorf("Application does not exist: %s referenced in a communication (%+v)", to, communication))
			}
		}
	}

	return errors.Join(errs...)
}

func (c Config) GetApplication(name string) (*Application, *Network, string) {
	if slices.Contains(PREDEFINED_APPS, name) {
		return nil, nil, name
	}
	for _, network := range c.Networks {
		if name == network.Name {
			return nil, network, ""
		}
	}
	for _, ns := range c.Namespaces {
		for _, app := range ns.Applications {
			if app.Name == name {
				return app, nil, ""
			}
		}
	}
	return nil, nil, ""
}

func LoadConfig(file string) (*Config, error) {
	fmt.Fprintf(os.Stderr, "Reading config %s\n", file)
	yamlFile, err := os.ReadFile(file)
	if err != nil {
		return nil, fmt.Errorf("Error reading YAML file: %v", err)
	}

	// Parse the YAML content
	dec := yaml.NewDecoder(bytes.NewReader(yamlFile),
		yaml.UseJSONUnmarshaler(),
		yaml.DisallowUnknownField(),
	)
	var config Config
	err = dec.Decode(&config)
	if err != nil {
		return nil, fmt.Errorf("Error parsing YAML: %v", err)
	}
	err = config.Validate()
	if err != nil {
		return nil, err
	}

	// every application must have its namespace field set
	for _, ns := range config.Namespaces {
		for _, app := range ns.Applications {
			app.Namespace = ns.Name
		}
	}

	return &config, nil
}