package provider

import (
	"strings"

	pb "code.hackerspace.pl/hscloud/bgpwtf/cccampix/proto"
)

// A raw, unparsed RPSL name/value pair.
type rpslRawAttribute struct {
	name  string
	value string
}

// parseAttributes converts raw RPSL attributes into parsed, structured protos.
func parseAttributes(attrs []rpslRawAttribute) []*pb.IRRAttribute {
	res := []*pb.IRRAttribute{}

	for _, attr := range attrs {
		switch attr.name {
		case "remarks":
			res = append(res, &pb.IRRAttribute{
				Value: &pb.IRRAttribute_Remarks{attr.value},
			})
		case "import":
			ie := parseImportExport(attr.value)
			if ie != nil {
				res = append(res, &pb.IRRAttribute{
					Value: &pb.IRRAttribute_Import{ie},
				})
			}
		case "export":
			ie := parseImportExport(attr.value)
			if ie != nil {
				res = append(res, &pb.IRRAttribute{
					Value: &pb.IRRAttribute_Export{ie},
				})
			}
		}
	}

	return res
}

// parseImportExport tries to parse the RPSL subset for import/export
// attributes.
// It's a hand-written single-pass parser which makes it not very good.
// See rpsl_test.go for examples.
func parseImportExport(expression string) *pb.IRRAttribute_ImportExport {
	popToken := func(s string) (string, string) {
		s = strings.TrimSpace(s)
		fields := strings.Fields(s)
		if len(fields) < 2 {
			return "", s
		}
		return fields[0], strings.TrimSpace(s[len(fields[0]):])
	}

	res := &pb.IRRAttribute_ImportExport{}

	expr := expression
	var t string
	t, expr = popToken(expr)

	for {
		switch t {
		case "":
			break
		case "protocol":
			t, expr = popToken(expr)
			res.ProtocolFrom = t
			t, expr = popToken(expr)
			continue
		case "into":
			t, expr = popToken(expr)
			res.ProtocolInto = t
			t, expr = popToken(expr)
			continue
		case "from":
			fallthrough
		case "to":
			t, expr = popToken(expr)
			peering := t
			actions := []string{}
			router_us := ""
			router_them := ""

			t2, expr2 := popToken(expr)
			for {
				switch t2 {
				case "at":
					t2, expr2 = popToken(expr2)
					router_us = t2
					t2, expr2 = popToken(expr2)
					continue
				case "action":
					parts := strings.SplitN(expr2, ";", 2)
					if len(parts) != 2 {
						// malformed action, no ';' found - bail
						return nil
					}
					actions = append(actions, parts[0])
					expr2 = strings.TrimSpace(parts[1])
					t2, expr2 = popToken(expr2)
					continue
				case "":
					fallthrough
				case "accept":
					fallthrough
				case "announce":
					t = t2
					expr = expr2
					break
				default:
					if router_them == "" {
						router_them = t2
						t2, expr2 = popToken(expr2)
						continue
					}
					t = t2
					expr = expr2
					break
				}
				break
			}
			res.Expressions = append(res.Expressions, &pb.IRRAttribute_ImportExport_Expression{
				Peering:    peering,
				RouterUs:   router_us,
				RouterThem: router_them,
				Actions:    actions,
			})
			continue
		case "accept":
			fallthrough
		case "announce":
			res.Filter = expr
			t = ""
			continue
		default:
			return nil
		}
		break
	}

	return res
}