package pipeline

import (
	"fmt"
	"net/netip"
	"sort"
	"strconv"
	"strings"

	"evobgp/internal/birdfmt"
	"evobgp/internal/store"
)

type staticCommunityRoutes struct {
	CommunityID string
	RoutesV4    []birdfmt.StaticRoute
	RoutesV6    []birdfmt.StaticRoute
}

// materializeRowsForBird turns prefix rows into export-filter CIDR lists, optional AS_PATH rules,
// and static routes grouped by community. The same prefix can appear in multiple community groups.
func materializeRowsForBird(st store.Backend, tenantID string, rows []store.PrefixRow) (
	filterV4, filterV6 []netip.Prefix,
	pathASNs []int64,
	staticByCommunity []staticCommunityRoutes,
	err error,
) {
	var pathSeen map[int64]struct{}
	addPath := func(n int64) {
		if pathSeen == nil {
			pathSeen = make(map[int64]struct{})
		}
		if _, ok := pathSeen[n]; ok {
			return
		}
		pathSeen[n] = struct{}{}
		pathASNs = append(pathASNs, n)
	}

	filterSeen := make(map[string]struct{})
	type staticGroup struct {
		v4 map[string]birdfmt.StaticRoute
		v6 map[string]birdfmt.StaticRoute
	}
	staticGroups := make(map[string]*staticGroup)
	routeBodyByCommunity := make(map[string]string)

	for _, pr := range rows {
		p := strings.TrimSpace(pr.Prefix)
		if strings.HasPrefix(p, "as:") {
			n, err := strconv.ParseInt(strings.TrimPrefix(p, "as:"), 10, 64)
			if err != nil || !store.ValidASN(n) {
				continue
			}
			addPath(n)
			continue
		}
		pfx, err := netip.ParsePrefix(p)
		if err != nil {
			continue
		}
		pfx = pfx.Masked()
		key := pfx.String()
		if _, ok := filterSeen[key]; !ok {
			filterSeen[key] = struct{}{}
			if pfx.Addr().Is4() {
				filterV4 = append(filterV4, pfx)
			} else {
				filterV6 = append(filterV6, pfx)
			}
		}

		communityID := ""
		if pr.CommunityID != nil {
			communityID = strings.TrimSpace(*pr.CommunityID)
		}
		body, ok := routeBodyByCommunity[communityID]
		if !ok {
			body, err = communityRouteBody(st, tenantID, pr.CommunityID)
			if err != nil {
				return nil, nil, nil, nil, err
			}
			routeBodyByCommunity[communityID] = body
		}
		grp, ok := staticGroups[communityID]
		if !ok {
			grp = &staticGroup{
				v4: make(map[string]birdfmt.StaticRoute),
				v6: make(map[string]birdfmt.StaticRoute),
			}
			staticGroups[communityID] = grp
		}
		if pfx.Addr().Is4() {
			if _, exists := grp.v4[key]; !exists {
				grp.v4[key] = birdfmt.StaticRoute{Prefix: pfx, RouteBody: body}
			}
		} else if pfx.Addr().Is6() {
			if _, exists := grp.v6[key]; !exists {
				grp.v6[key] = birdfmt.StaticRoute{Prefix: pfx, RouteBody: body}
			}
		}
	}

	groupKeys := make([]string, 0, len(staticGroups))
	for k := range staticGroups {
		groupKeys = append(groupKeys, k)
	}
	sort.Strings(groupKeys)

	for _, gid := range groupKeys {
		grp := staticGroups[gid]
		out := staticCommunityRoutes{CommunityID: gid}

		v4Keys := make([]string, 0, len(grp.v4))
		for k := range grp.v4 {
			v4Keys = append(v4Keys, k)
		}
		sort.Strings(v4Keys)
		for _, k := range v4Keys {
			out.RoutesV4 = append(out.RoutesV4, grp.v4[k])
		}

		v6Keys := make([]string, 0, len(grp.v6))
		for k := range grp.v6 {
			v6Keys = append(v6Keys, k)
		}
		sort.Strings(v6Keys)
		for _, k := range v6Keys {
			out.RoutesV6 = append(out.RoutesV6, grp.v6[k])
		}
		staticByCommunity = append(staticByCommunity, out)
	}
	return filterV4, filterV6, pathASNs, staticByCommunity, nil
}

func communityRouteBody(st store.Backend, tenantID string, cid *string) (string, error) {
	if cid == nil {
		return "", nil
	}
	id := strings.TrimSpace(*cid)
	if id == "" {
		return "", nil
	}
	c, err := st.GetCommunity(tenantID, id)
	if err != nil {
		return "", fmt.Errorf("community %s: %w", id, err)
	}
	return birdfmt.RouteCommunityAttrs("", c.Community, c.ValueJSON)
}