// Package validate checks a complete configuration State for problems
// before it is rendered and handed to BIND.
//
// Rules come from the DNS RFCs (CNAME exclusivity, glue, DNAME, ...), from
// the checks named itself performs when loading a zone (check-names,
// check-integrity, record limits), and from operational experience (open
// resolvers, open zone transfers). named-checkconf and named-checkzone are
// run as well before anything is applied; this package exists so that
// problems are found early and explained in terms of Jarl objects.
package validate

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

	"jarl/internal/dnsname"
	"jarl/internal/model"
)

// Severity of a problem.
type Severity string

const (
	Error   Severity = "error"   // blocks applying
	Warning Severity = "warning" // shown, does not block
	Info    Severity = "info"
)

// Problem is a single validation finding.
type Problem struct {
	Severity   Severity `json:"severity"`
	Code       string   `json:"code"`
	Message    string   `json:"message"`
	ObjectType string   `json:"object_type,omitempty"` // view, zone, record, acl, key, option, settings
	ObjectID   int64    `json:"object_id,omitempty"`
	Zone       string   `json:"zone,omitempty"`
	View       string   `json:"view,omitempty"`
	Name       string   `json:"name,omitempty"`
	// Acknowledged is set when an exposure finding was accepted on
	// purpose (it is then info, not a warning).
	Acknowledged *model.Acknowledgement `json:"acknowledged,omitempty"`
}

// Key identifies a problem independently of object IDs, so problems can be
// compared between two states.
func (p Problem) Key() string {
	return string(p.Severity) + "|" + p.Code + "|" + p.View + "|" + p.Zone + "|" + p.Name + "|" + p.Message
}

func (p Problem) String() string {
	loc := ""
	if p.Zone != "" {
		loc = "zone " + dnsname.Display(p.Zone)
		if p.View != "" {
			loc += " [view " + p.View + "]"
		}
		loc += ": "
	} else if p.View != "" {
		loc = "view " + p.View + ": "
	}
	return string(p.Severity) + ": " + loc + p.Message
}

// Options adjust validation.
type Options struct {
	// ExternalKeys are TSIG key names defined outside Jarl, in files
	// pulled in by top-level include statements (e.g. rndc-key).
	ExternalKeys []string
	// ExternalKeysUnknown is set when an included file could not be read,
	// so references to unknown keys are not reported.
	ExternalKeysUnknown bool
	// LocalAddrs are this host's addresses: a server without views is
	// public when named listens on one that isn't private
	// (docs/exposure.md).
	LocalAddrs []netip.Addr
}

// Result holds the problems found.
type Result struct {
	Problems []Problem `json:"problems"`
}

// HasErrors reports whether any problem is an error.
func HasErrors(ps []Problem) bool {
	for _, p := range ps {
		if p.Severity == Error {
			return true
		}
	}
	return false
}

// Errors returns only the errors.
func Errors(ps []Problem) []Problem {
	var out []Problem
	for _, p := range ps {
		if p.Severity == Error {
			out = append(out, p)
		}
	}
	return out
}

// Introduced returns the problems in after that are not in before.
func Introduced(before, after []Problem) []Problem {
	seen := map[string]bool{}
	for _, p := range before {
		seen[p.Key()] = true
	}
	var out []Problem
	for _, p := range after {
		if !seen[p.Key()] {
			out = append(out, p)
		}
	}
	return out
}

type checker struct {
	s        *model.State
	opts     Options
	problems []Problem
	// indexes
	zoneRecords map[int64][]*model.Record // served records (not disabled)
	allRecords  map[int64][]*model.Record
	keyNames    map[string]bool
}

// State validates the complete state.
func State(s *model.State, opts Options) []Problem {
	c := &checker{s: s, opts: opts, zoneRecords: s.ServedRecordsByZone(), allRecords: s.RecordsByZone(), keyNames: map[string]bool{}}
	for _, k := range s.Keys {
		c.keyNames[k.Name] = true
	}
	// The views' own keys (render/viewkeys.go) may be referred to too.
	for _, v := range s.Views {
		c.keyNames[model.NormalizeKeyName(model.ViewKeyName(v.Name))] = true
	}
	for _, k := range opts.ExternalKeys {
		c.keyNames[model.NormalizeKeyName(k)] = true
	}
	c.checkSettings()
	c.checkKeys()
	c.checkACLs()
	c.checkViews()
	c.checkZones()
	c.checkOptions()
	c.checkSecurity()
	c.checkExposure()
	c.checkDNSSEC()
	c.checkBlocking()
	c.checkLinked()
	c.checkTLSFiles()
	c.applyAcks()
	sortProblems(c.problems)
	return c.problems
}

func (c *checker) add(p Problem) { c.problems = append(c.problems, p) }

func (c *checker) errf(code, objType string, id int64, format string, args ...any) *Problem {
	c.add(Problem{Severity: Error, Code: code, ObjectType: objType, ObjectID: id, Message: fmt.Sprintf(format, args...)})
	return &c.problems[len(c.problems)-1]
}

func (c *checker) warnf(code, objType string, id int64, format string, args ...any) *Problem {
	c.add(Problem{Severity: Warning, Code: code, ObjectType: objType, ObjectID: id, Message: fmt.Sprintf(format, args...)})
	return &c.problems[len(c.problems)-1]
}

func (c *checker) infof(code, objType string, id int64, format string, args ...any) *Problem {
	c.add(Problem{Severity: Info, Code: code, ObjectType: objType, ObjectID: id, Message: fmt.Sprintf(format, args...)})
	return &c.problems[len(c.problems)-1]
}

func sortProblems(ps []Problem) {
	rank := map[Severity]int{Error: 0, Warning: 1, Info: 2}
	sort.SliceStable(ps, func(i, j int) bool {
		a, b := ps[i], ps[j]
		if rank[a.Severity] != rank[b.Severity] {
			return rank[a.Severity] < rank[b.Severity]
		}
		if a.View != b.View {
			return a.View < b.View
		}
		if a.Zone != b.Zone {
			return a.Zone < b.Zone
		}
		if a.Name != b.Name {
			return model.NameLess(a.Name, b.Name)
		}
		return a.Message < b.Message
	})
}

// zoneLabel returns "name [view]" for messages.
func (c *checker) zoneLabel(z *model.Zone) string {
	if v := c.s.ViewName(z); v != "" {
		return strings.TrimSuffix(z.Name, ".") + " [view " + v + "]"
	}
	return strings.TrimSuffix(z.Name, ".")
}