// This file is part of the happyDomain (R) project.
// Copyright (c) 2020-2026 happyDomain
// Authors: Pierre-Olivier Mercier, et al.
//
// This program is offered under a commercial and under the AGPL license.
// For commercial licensing, contact us at <contact@happydomain.org>.
//
// For AGPL licensing:
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

package checker

import (
	"context"
	"fmt"
	"strings"

	sdk "git.happydns.org/checker-sdk-go/checker"
)

// Single-priority with multiple targets is Info (not Warn) because it is legal; all-zero-weight within a group is Warn because it almost always indicates a misconfiguration.

type rulePriorityWeightSanity struct{}

func RulePriorityWeightSanity() sdk.CheckRule { return &rulePriorityWeightSanity{} }
func (rulePriorityWeightSanity) Name() string { return "srv_priority_weight_sanity" }
func (rulePriorityWeightSanity) Description() string {
	return "Priority/weight values follow RFC 2782 conventions (failover present, weights meaningful)."
}
func (rulePriorityWeightSanity) Evaluate(ctx context.Context, obs sdk.ObservationGetter, _ sdk.CheckerOptions) []sdk.CheckState {
	d, cs := getData(ctx, obs)
	if cs != nil {
		return []sdk.CheckState{*cs}
	}

	type groupKey struct{ owner string }
	type group struct {
		priorities map[uint16]int
		zeroWeight map[uint16]int
	}
	groups := map[groupKey]*group{}
	for _, r := range d.Records {
		if r.IsNullTarget {
			continue
		}
		k := groupKey{owner: r.Owner}
		g := groups[k]
		if g == nil {
			g = &group{priorities: map[uint16]int{}, zeroWeight: map[uint16]int{}}
			groups[k] = g
		}
		g.priorities[r.Priority]++
		if r.Weight == 0 {
			g.zeroWeight[r.Priority]++
		}
	}

	if len(groups) == 0 {
		return []sdk.CheckState{{Status: sdk.StatusInfo, Code: "srv_prio_weight_na",
			Message: "No active SRV records to analyse."}}
	}

	var noFailover []string
	var zeroWeightGroups []string
	for k, g := range groups {
		if len(g.priorities) < 2 {
			total := 0
			for _, c := range g.priorities {
				total += c
			}
			if total > 1 {
				noFailover = append(noFailover, k.owner)
			}
		}
		for prio, zc := range g.zeroWeight {
			if zc > 1 && zc == g.priorities[prio] {
				zeroWeightGroups = append(zeroWeightGroups, fmt.Sprintf("%s@prio=%d", k.owner, prio))
			}
		}
	}

	var out []sdk.CheckState
	if len(zeroWeightGroups) > 0 {
		out = append(out, sdk.CheckState{Status: sdk.StatusWarn, Code: "srv_weight_all_zero",
			Message: fmt.Sprintf("Priority group(s) with multiple targets all weighted 0: %s", strings.Join(zeroWeightGroups, ", "))})
	}
	if len(noFailover) > 0 {
		out = append(out, sdk.CheckState{Status: sdk.StatusInfo, Code: "srv_single_priority",
			Message: fmt.Sprintf("Service(s) with multiple records but a single priority tier (no failover): %s", strings.Join(noFailover, ", "))})
	}
	if len(out) == 0 {
		out = append(out, sdk.CheckState{Status: sdk.StatusOK, Code: "srv_prio_weight_ok",
			Message: "Priority and weight values are consistent with RFC 2782 conventions."})
	}
	return out
}