package model

import (
	"fmt"
	"net/netip"
	"slices"
	"sort"
	"strings"
	"time"
)

// Blocklist is a list of domains to block, downloaded from URL and kept up
// to date by jarld (docs/blocking.md).
type Blocklist struct {
	ID   int64  `json:"id"`
	Name string `json:"name"` // a DNS label: it names the list's policy zone
	URL  string `json:"url"`
	// ViewIDs are the views the list applies to; empty means every view
	// that offers recursion (see BlockingViews).
	ViewIDs  []int64 `json:"view_ids"`
	Disabled bool    `json:"disabled,omitempty"`
	// StepID is the blocking step the list starts at: StepNormal for
	// every client, or a BlockStep for the clients of groups at that step
	// or above.
	StepID  int64  `json:"step_id"`
	Comment string `json:"comment"`
	Meta
}

// Built-in blocking steps (BlockStep IDs are positive).
const (
	StepOff    int64 = -1 // no blocklists (rules still apply)
	StepNormal int64 = 0  // the default: every client not in a group
)

// BlockStep is a blocking step above Normal. Steps are ordered: each
// includes the lists of the steps below it, plus its own (docs/blocking.md).
type BlockStep struct {
	ID       int64  `json:"id"`
	Name     string `json:"name"`
	Position int    `json:"position"`
	Comment  string `json:"comment"`
	Meta
}

// ClientGroup gives the clients with these addresses a blocking step.
type ClientGroup struct {
	ID   int64  `json:"id"`
	Name string `json:"name"`
	// Members are addresses, prefixes, or names of ACLs made of them.
	Members []string `json:"members"`
	StepID  int64    `json:"step_id"`  // StepOff, StepNormal or a BlockStep
	ViewIDs []int64  `json:"view_ids"` // as for Blocklist
	Comment string   `json:"comment"`
	Meta
}

// OrderedBlockSteps returns the steps above Normal, lowest first.
func (s *State) OrderedBlockSteps() []*BlockStep {
	out := make([]*BlockStep, 0, len(s.BlockSteps))
	for _, st := range s.BlockSteps {
		out = append(out, st)
	}
	sort.Slice(out, func(i, j int) bool {
		if out[i].Position != out[j].Position {
			return out[i].Position < out[j].Position
		}
		return out[i].ID < out[j].ID
	})
	return out
}

// StepRank orders steps: -1 for Off, 0 for Normal, 1, 2, ... for the
// steps above it. ok is false for a step that doesn't exist.
func (s *State) StepRank(id int64) (rank int, ok bool) {
	switch id {
	case StepOff:
		return -1, true
	case StepNormal:
		return 0, true
	}
	for i, st := range s.OrderedBlockSteps() {
		if st.ID == id {
			return i + 1, true
		}
	}
	return 0, false
}

// StepName returns a step's name ("off" and "normal" for the built-in
// ones).
func (s *State) StepName(id int64) string {
	switch id {
	case StepOff:
		return "off"
	case StepNormal:
		return "normal"
	}
	if st := s.BlockSteps[id]; st != nil {
		return st.Name
	}
	return fmt.Sprintf("step %d", id)
}

// StepByName finds a step by name, the built-in ones included.
func (s *State) StepByName(name string) (int64, bool) {
	name = strings.ToLower(strings.TrimSpace(name))
	switch name {
	case "off":
		return StepOff, true
	case "normal":
		return StepNormal, true
	}
	for _, st := range s.BlockSteps {
		if strings.EqualFold(st.Name, name) {
			return st.ID, true
		}
	}
	return 0, false
}

// ClientGroupByName finds a client group by name.
func (s *State) ClientGroupByName(name string) *ClientGroup {
	for _, g := range s.ClientGroups {
		if strings.EqualFold(g.Name, name) {
			return g
		}
	}
	return nil
}

// SortedClientGroups returns the client groups ordered by name.
func (s *State) SortedClientGroups() []*ClientGroup {
	out := make([]*ClientGroup, 0, len(s.ClientGroups))
	for _, g := range s.ClientGroups {
		out = append(out, g)
	}
	sort.Slice(out, func(i, j int) bool { return out[i].Name < out[j].Name })
	return out
}

// Block rule actions.
const (
	BlockActionBlock = "block"
	BlockActionAllow = "allow"
)

// BlockRule blocks or allows a domain, and unless Exact the names below
// it. Rules take precedence over blocklists.
type BlockRule struct {
	ID      int64   `json:"id"`
	Name    string  `json:"name"`   // lowercase, without the final dot
	Action  string  `json:"action"` // block or allow
	Exact   bool    `json:"exact,omitempty"`
	ViewIDs []int64 `json:"view_ids"` // as for Blocklist
	Comment string  `json:"comment"`
	Meta
}

// BlocklistStatus is what jarld knows about a list's downloads. It is not
// configuration: it is kept outside changesets.
type BlocklistStatus struct {
	ID           int64      `json:"id"`
	URL          string     `json:"url"` // the URL last tried
	ETag         string     `json:"-"`
	LastModified string     `json:"-"`
	CheckedAt    *time.Time `json:"checked_at,omitempty"` // last attempt
	UpdatedAt    *time.Time `json:"updated_at,omitempty"` // last time the content changed
	Entries      int        `json:"entries"`              // domains
	Records      int        `json:"records"`              // policy zone records
	Skipped      int        `json:"skipped"`              // lines that weren't usable
	SHA256       string     `json:"-"`
	Error        string     `json:"error,omitempty"` // the last attempt failed
}

// BlocklistByName finds a blocklist by name.
func (s *State) BlocklistByName(name string) *Blocklist {
	for _, b := range s.Blocklists {
		if strings.EqualFold(b.Name, name) {
			return b
		}
	}
	return nil
}

// SortedBlocklists returns the blocklists ordered by name.
func (s *State) SortedBlocklists() []*Blocklist {
	out := make([]*Blocklist, 0, len(s.Blocklists))
	for _, b := range s.Blocklists {
		out = append(out, b)
	}
	sort.Slice(out, func(i, j int) bool { return out[i].Name < out[j].Name })
	return out
}

// SortedBlockRules returns the rules ordered by domain, parents first.
func (s *State) SortedBlockRules() []*BlockRule {
	out := make([]*BlockRule, 0, len(s.BlockRules))
	for _, r := range s.BlockRules {
		out = append(out, r)
	}
	sort.Slice(out, func(i, j int) bool {
		a, b := out[i], out[j]
		if a.Name != b.Name {
			return CanonicalLess(a.Name+".", b.Name+".")
		}
		if a.Exact != b.Exact {
			return !a.Exact
		}
		return a.ID < b.ID
	})
	return out
}

// RecursionOn reports whether a view (0: the server without views) offers
// recursion: its recursion option, else the server's, else BIND's default
// (yes).
func (s *State) RecursionOn(viewID int64) bool {
	o := s.FindOption(ScopeView, viewID, "recursion")
	if viewID == 0 || o == nil {
		if g := s.FindOption(ScopeOptions, 0, "recursion"); o == nil {
			o = g
		}
	}
	if o == nil {
		return true
	}
	switch strings.ToLower(strings.Trim(strings.TrimSpace(o.Value), `";`)) {
	case "no", "false", "0":
		return false
	}
	return true
}

// BlockingViews returns the views a blocklist or rule with viewIDs applies
// to, in view order: the given views, or when none are given every view
// that offers recursion (blocking only affects recursive queries). Without
// views it returns []int64{0}, the whole server, if it offers recursion.
func (s *State) BlockingViews(viewIDs []int64) []int64 {
	views := s.OrderedViews()
	if len(views) == 0 {
		if !s.RecursionOn(0) {
			return nil
		}
		return []int64{0}
	}
	var out []int64
	for _, v := range views {
		if len(viewIDs) == 0 && s.RecursionOn(v.ID) || slices.Contains(viewIDs, v.ID) {
			out = append(out, v.ID)
		}
	}
	return out
}

// GroupPrefixes returns the addresses of a client group as prefixes: its
// own, and those of the ACLs it names (and the ACLs they name). Elements
// that aren't addresses are left out (validation reports them).
func (s *State) GroupPrefixes(g *ClientGroup) []netip.Prefix {
	var out []netip.Prefix
	seen := map[string]bool{}
	var add func(elems []string)
	add = func(elems []string) {
		for _, e := range elems {
			e = strings.TrimSpace(e)
			if a, err := netip.ParseAddr(e); err == nil {
				a = a.Unmap()
				out = append(out, netip.PrefixFrom(a, a.BitLen()))
			} else if p, err := netip.ParsePrefix(e); err == nil {
				out = append(out, p.Masked())
			} else if acl := s.ACLByName(e); acl != nil && !seen[acl.Name] {
				seen[acl.Name] = true
				add(acl.Elements)
			}
		}
	}
	add(g.Members)
	return out
}