package birdfmt

import (
	"strconv"
	"strings"
)

// BGPSession is one BGP protocol block from `birdc show protocols all`.
type BGPSession struct {
	Name       string `json:"name"`
	Neighbor   string `json:"neighbor,omitempty"`
	NeighborAS int64  `json:"neighbor_as,omitempty"`
	NeighborID string `json:"neighbor_id,omitempty"`
	State      string `json:"state"`
}

// DynamicPeerProtocolPrefix is the BIRD protocol name prefix for discovery-spawned sessions.
const DynamicPeerProtocolPrefix = "evobgp_dyn_"

// IsDynamicDiscoverySession reports whether the protocol was spawned by the discovery listener.
func IsDynamicDiscoverySession(name string) bool {
	return strings.HasPrefix(strings.TrimSpace(name), DynamicPeerProtocolPrefix)
}

// ParseBGPSessions extracts BGP protocol name, state, neighbor, Neighbor AS, and Neighbor ID from birdc output.
func ParseBGPSessions(output string) []BGPSession {
	var out []BGPSession
	var cur *BGPSession
	for _, raw := range strings.Split(output, "\n") {
		line := strings.TrimRight(raw, "\r")
		trim := strings.TrimSpace(line)
		if trim == "" {
			cur = nil
			continue
		}
		low := strings.ToLower(trim)
		if strings.HasPrefix(low, "bird ") || strings.HasPrefix(low, "name ") || strings.HasPrefix(low, "table ") {
			continue
		}
		if !strings.HasPrefix(line, " ") && !strings.HasPrefix(line, "\t") {
			if isBGPProtocolSummaryRow(trim) {
				fields := strings.Fields(trim)
				state := extractBGPSessionStateLine(trim)
				if state == "" && len(fields) >= 4 {
					state = fields[3]
				}
				out = append(out, BGPSession{Name: fields[0], State: state})
				cur = &out[len(out)-1]
			} else {
				cur = nil
			}
			continue
		}
		if cur == nil {
			continue
		}
		parseBGPSessionDetailLine(cur, trim)
	}
	return out
}

func parseBGPSessionDetailLine(cur *BGPSession, trim string) {
	for _, prefix := range []string{"Neighbor address:", "Neighbor Address:", "Neighbor:"} {
		if idx := strings.Index(trim, prefix); idx >= 0 {
			// Avoid matching "Neighbor AS:" / "Neighbor ID:" via bare "Neighbor:"
			if prefix == "Neighbor:" {
				rest := strings.TrimSpace(trim[idx+len(prefix):])
				if strings.HasPrefix(strings.ToLower(rest), "as:") || strings.HasPrefix(strings.ToLower(rest), "id:") {
					continue
				}
				if strings.Contains(strings.ToLower(trim), "neighbor as:") || strings.Contains(strings.ToLower(trim), "neighbor id:") {
					continue
				}
			}
			cur.Neighbor = strings.TrimSpace(trim[idx+len(prefix):])
			return
		}
	}
	for _, prefix := range []string{"Neighbor AS:", "Neighbor As:", "Neighbor as:"} {
		if idx := strings.Index(trim, prefix); idx >= 0 {
			raw := strings.TrimSpace(trim[idx+len(prefix):])
			if n, err := strconv.ParseInt(raw, 10, 64); err == nil {
				cur.NeighborAS = n
			}
			return
		}
	}
	for _, prefix := range []string{"Neighbor ID:", "Neighbor Id:", "Neighbor id:", "BGP Identifier:", "BGP identifier:"} {
		if idx := strings.Index(trim, prefix); idx >= 0 {
			cur.NeighborID = strings.TrimSpace(trim[idx+len(prefix):])
			return
		}
	}
}