package agent

import (
	"fmt"
	"net"
	"strings"

	"code.fritzlab.net/fritzlab/flock/pkg/embed"
)

const annotationPrefix = "flock.fritzlab.net/"

// ParsedAnnotations is the typed view of a Pod's flock annotations.
type ParsedAnnotations struct {
	WantV6   bool
	WantV4   bool
	CIDR6    []*net.IPNet
	CIDR4    []*net.IPNet
	IPAlgo   []embed.Field
	Anycast  []net.IP
}

// ParseAnnotations applies the design-doc defaults (ipv6=true, ipv4=false)
// and validates the post-merge combination.
func ParseAnnotations(in map[string]string) (*ParsedAnnotations, error) {
	out := &ParsedAnnotations{WantV6: true, WantV4: false}

	if v, ok := in[annotationPrefix+"ipv6"]; ok {
		switch strings.ToLower(strings.TrimSpace(v)) {
		case "true":
			out.WantV6 = true
		case "false":
			out.WantV6 = false
		default:
			return nil, fmt.Errorf("annotation ipv6=%q: must be true or false", v)
		}
	}
	if v, ok := in[annotationPrefix+"ipv4"]; ok {
		switch strings.ToLower(strings.TrimSpace(v)) {
		case "true":
			out.WantV4 = true
		case "false":
			out.WantV4 = false
		default:
			return nil, fmt.Errorf("annotation ipv4=%q: must be true or false", v)
		}
	}
	if !out.WantV6 && !out.WantV4 {
		return nil, fmt.Errorf("ipv6=false requires ipv4=true (pod must have at least one address)")
	}

	if v, ok := in[annotationPrefix+"cidr6"]; ok {
		nets, err := parseCIDRList(v)
		if err != nil {
			return nil, fmt.Errorf("annotation cidr6: %w", err)
		}
		out.CIDR6 = nets
	}
	if v, ok := in[annotationPrefix+"cidr4"]; ok {
		nets, err := parseCIDRList(v)
		if err != nil {
			return nil, fmt.Errorf("annotation cidr4: %w", err)
		}
		out.CIDR4 = nets
	}

	if v, ok := in[annotationPrefix+"ip-algo"]; ok {
		fields, err := parseIPAlgo(v)
		if err != nil {
			return nil, fmt.Errorf("annotation ip-algo: %w", err)
		}
		out.IPAlgo = fields
	}

	if v, ok := in[annotationPrefix+"anycast"]; ok {
		ips, err := parseIPList(v)
		if err != nil {
			return nil, fmt.Errorf("annotation anycast: %w", err)
		}
		out.Anycast = ips
	}

	return out, nil
}

func parseCIDRList(s string) ([]*net.IPNet, error) {
	var out []*net.IPNet
	for _, part := range strings.Split(s, ",") {
		part = strings.TrimSpace(part)
		if part == "" {
			continue
		}
		_, n, err := net.ParseCIDR(part)
		if err != nil {
			return nil, fmt.Errorf("invalid CIDR %q: %w", part, err)
		}
		out = append(out, n)
	}
	if len(out) == 0 {
		return nil, fmt.Errorf("empty CIDR list")
	}
	return out, nil
}

func parseIPList(s string) ([]net.IP, error) {
	var out []net.IP
	for _, part := range strings.Split(s, ",") {
		part = strings.TrimSpace(part)
		if part == "" {
			continue
		}
		ip := net.ParseIP(part)
		if ip == nil {
			return nil, fmt.Errorf("invalid IP %q", part)
		}
		out = append(out, ip)
	}
	if len(out) == 0 {
		return nil, fmt.Errorf("empty IP list")
	}
	return out, nil
}

func parseIPAlgo(s string) ([]embed.Field, error) {
	var out []embed.Field
	for _, part := range strings.Split(s, ",") {
		part = strings.TrimSpace(part)
		switch part {
		case "":
			continue
		case "namespace":
			out = append(out, embed.FieldNamespace)
		case "pod":
			out = append(out, embed.FieldPod)
		case "image":
			out = append(out, embed.FieldImage)
		default:
			return nil, fmt.Errorf("unknown ip-algo field %q (allowed: namespace, pod, image)", part)
		}
	}
	if len(out) == 0 {
		return nil, fmt.Errorf("empty ip-algo")
	}
	return out, nil
}

// CNIArgs parses the K=V;K=V CNI_ARGS string for the kubelet keys we care
// about. Other keys are ignored.
type CNIArgs struct {
	PodNamespace string
	PodName      string
	PodUID       string
	InfraID      string
}

func ParseCNIArgs(s string) CNIArgs {
	var a CNIArgs
	for _, kv := range strings.Split(s, ";") {
		eq := strings.IndexByte(kv, '=')
		if eq < 0 {
			continue
		}
		k, v := kv[:eq], kv[eq+1:]
		switch k {
		case "K8S_POD_NAMESPACE":
			a.PodNamespace = v
		case "K8S_POD_NAME":
			a.PodName = v
		case "K8S_POD_UID":
			a.PodUID = v
		case "K8S_POD_INFRA_CONTAINER_ID":
			a.InfraID = v
		}
	}
	return a
}