package app

import (
	"context"
	"errors"
	"fmt"
	"io"
	"strings"

	"github.com/owen/vibedns/internal/auditlog"
	"github.com/owen/vibedns/internal/blacklist"
	"github.com/owen/vibedns/internal/config"
	"github.com/owen/vibedns/internal/database"
	"github.com/owen/vibedns/internal/models"
	"github.com/owen/vibedns/internal/validate"
)

// --- Client networks ----------------------------------------------------

// NetworkInput is the editable surface of a client network.
type NetworkInput struct {
	Name        string  `json:"name"`
	CIDR        string  `json:"cidr"`
	Description string  `json:"description"`
	Enabled     *bool   `json:"enabled"`
	PolicyIDs   []int64 `json:"policy_ids"`
}

// Networks lists client networks with their policy assignments.
func (a *App) Networks(ctx context.Context, search string) ([]models.Network, error) {
	nets, err := a.DB.Networks(ctx, search, true)
	if err != nil {
		return nil, Internal(err, "The network list could not be loaded.")
	}
	return nets, nil
}

// Network loads one client network.
func (a *App) Network(ctx context.Context, id int64) (models.Network, error) {
	n, err := a.DB.Network(ctx, id)
	if errors.Is(err, database.ErrNotFound) {
		return n, NotFound("Network %d was not found.", id)
	}
	if err != nil {
		return n, Internal(err, "The network could not be loaded.")
	}
	return n, nil
}

func (a *App) normaliseNetwork(in NetworkInput, base models.Network) (models.Network, error) {
	n := base
	if name := strings.TrimSpace(in.Name); name != "" {
		n.Name = name
	}
	if n.Name == "" {
		return n, Invalid("A network name is required.")
	}
	if cidr := strings.TrimSpace(in.CIDR); cidr != "" {
		p, err := config.ParseCIDROrIP(cidr)
		if err != nil {
			return n, Invalid("Subnet %q: %s", cidr, err.Error())
		}
		n.CIDR = p.String()
	}
	if n.CIDR == "" {
		return n, Invalid("A subnet in CIDR notation is required, for example 192.168.1.0/24.")
	}
	n.Description = strings.TrimSpace(in.Description)
	if in.Enabled != nil {
		n.Enabled = *in.Enabled
	} else if base.ID == 0 {
		n.Enabled = true
	}
	return n, nil
}

// CreateNetwork stores a client network.
func (a *App) CreateNetwork(ctx context.Context, actor auditlog.Actor, in NetworkInput) (models.Network, error) {
	n, err := a.normaliseNetwork(in, models.Network{})
	if err != nil {
		return models.Network{}, err
	}
	created, err := a.DB.CreateNetwork(ctx, n, in.PolicyIDs)
	if err != nil {
		return models.Network{}, translate(err, "Network not found.",
			fmt.Sprintf("A network named %q already exists.", n.Name))
	}
	a.Audit.RecordID(ctx, actor, "network.create", auditlog.ObjectNetwork, created.ID, created.Name,
		auditlog.Changes("cidr", created.CIDR, "policies", fmt.Sprint(len(in.PolicyIDs))))
	a.Runtime.RequestReload()
	return created, nil
}

// UpdateNetwork saves a client network and its policy assignments.
func (a *App) UpdateNetwork(ctx context.Context, actor auditlog.Actor, id int64, in NetworkInput) (models.Network, error) {
	existing, err := a.Network(ctx, id)
	if err != nil {
		return models.Network{}, err
	}
	n, err := a.normaliseNetwork(in, existing)
	if err != nil {
		return models.Network{}, err
	}
	n.ID = id
	updated, err := a.DB.UpdateNetwork(ctx, n, in.PolicyIDs)
	if err != nil {
		return models.Network{}, translate(err, fmt.Sprintf("Network %d was not found.", id),
			fmt.Sprintf("A network named %q already exists.", n.Name))
	}
	a.Audit.RecordID(ctx, actor, "network.update", auditlog.ObjectNetwork, id, updated.Name,
		auditlog.Changes("cidr", updated.CIDR, "policies", fmt.Sprint(len(in.PolicyIDs))))
	a.Runtime.RequestReload()
	return updated, nil
}

// SetNetworkEnabled toggles a client network.
func (a *App) SetNetworkEnabled(ctx context.Context, actor auditlog.Actor, id int64, enabled bool) error {
	n, err := a.Network(ctx, id)
	if err != nil {
		return err
	}
	if err := a.DB.SetNetworkEnabled(ctx, id, enabled); err != nil {
		return translate(err, fmt.Sprintf("Network %d was not found.", id), "")
	}
	action := "network.disable"
	if enabled {
		action = "network.enable"
	}
	a.Audit.RecordID(ctx, actor, action, auditlog.ObjectNetwork, id, n.Name, "")
	a.Runtime.RequestReload()
	return nil
}

// DeleteNetwork removes a client network.
func (a *App) DeleteNetwork(ctx context.Context, actor auditlog.Actor, id int64) error {
	n, err := a.Network(ctx, id)
	if err != nil {
		return err
	}
	if err := a.DB.DeleteNetwork(ctx, id); err != nil {
		return translate(err, fmt.Sprintf("Network %d was not found.", id), "")
	}
	a.Audit.RecordID(ctx, actor, "network.delete", auditlog.ObjectNetwork, id, n.Name,
		auditlog.Changes("cidr", n.CIDR))
	a.Runtime.RequestReload()
	return nil
}

// --- Policies -----------------------------------------------------------

// PolicyInput is the editable surface of a policy.
type PolicyInput struct {
	Name         string  `json:"name"`
	Description  string  `json:"description"`
	Enabled      *bool   `json:"enabled"`
	BlockAction  string  `json:"block_action"`
	SinkholeIPv4 string  `json:"sinkhole_ipv4"`
	SinkholeIPv6 string  `json:"sinkhole_ipv6"`
	BlockTTL     uint32  `json:"block_ttl"`
	ListIDs      []int64 `json:"list_ids"`
}

// Policies lists every policy.
func (a *App) Policies(ctx context.Context) ([]models.Policy, error) {
	p, err := a.DB.Policies(ctx)
	if err != nil {
		return nil, Internal(err, "The policy list could not be loaded.")
	}
	return p, nil
}

// Policy loads one policy.
func (a *App) Policy(ctx context.Context, id int64) (models.Policy, error) {
	p, err := a.DB.Policy(ctx, id)
	if errors.Is(err, database.ErrNotFound) {
		return p, NotFound("Policy %d was not found.", id)
	}
	if err != nil {
		return p, Internal(err, "The policy could not be loaded.")
	}
	return p, nil
}

func (a *App) normalisePolicy(in PolicyInput, base models.Policy) (models.Policy, error) {
	p := base
	if name := strings.TrimSpace(in.Name); name != "" {
		p.Name = name
	}
	if p.Name == "" {
		return p, Invalid("A policy name is required.")
	}
	p.Description = strings.TrimSpace(in.Description)

	action := models.BlockAction(strings.ToLower(strings.TrimSpace(in.BlockAction)))
	if action == "" {
		action = base.BlockAction
	}
	if action == "" {
		action = models.BlockNXDOMAIN
	}
	if !action.Valid() {
		return p, Invalid("Block action %q must be nxdomain, refused or sinkhole.", in.BlockAction)
	}
	p.BlockAction = action

	p.SinkholeIPv4 = strings.TrimSpace(in.SinkholeIPv4)
	if p.SinkholeIPv4 == "" {
		p.SinkholeIPv4 = "0.0.0.0"
	}
	p.SinkholeIPv6 = strings.TrimSpace(in.SinkholeIPv6)
	if p.SinkholeIPv6 == "" {
		p.SinkholeIPv6 = "::"
	}
	if action == models.BlockSinkhole {
		if err := requireIP(p.SinkholeIPv4, true); err != nil {
			return p, Invalid("Sinkhole IPv4 address: %s", err.Error())
		}
		if err := requireIP(p.SinkholeIPv6, false); err != nil {
			return p, Invalid("Sinkhole IPv6 address: %s", err.Error())
		}
	}

	p.BlockTTL = in.BlockTTL
	if p.BlockTTL == 0 {
		p.BlockTTL = base.BlockTTL
	}
	if p.BlockTTL == 0 {
		p.BlockTTL = 60
	}
	if p.BlockTTL > 86400 {
		return p, Invalid("The block TTL must be 86400 seconds or less.")
	}

	if in.Enabled != nil {
		p.Enabled = *in.Enabled
	} else if base.ID == 0 {
		p.Enabled = true
	}
	return p, nil
}

func requireIP(s string, wantV4 bool) error {
	p, err := config.ParseCIDROrIP(s)
	if err != nil {
		return errors.New("must be a valid IP address")
	}
	if p.Addr().Is4() != wantV4 {
		if wantV4 {
			return errors.New("must be an IPv4 address")
		}
		return errors.New("must be an IPv6 address")
	}
	return nil
}

// CreatePolicy stores a policy.
func (a *App) CreatePolicy(ctx context.Context, actor auditlog.Actor, in PolicyInput) (models.Policy, error) {
	p, err := a.normalisePolicy(in, models.Policy{})
	if err != nil {
		return models.Policy{}, err
	}
	created, err := a.DB.CreatePolicy(ctx, p, in.ListIDs)
	if err != nil {
		return models.Policy{}, translate(err, "Policy not found.",
			fmt.Sprintf("A policy named %q already exists.", p.Name))
	}
	a.Audit.RecordID(ctx, actor, "policy.create", auditlog.ObjectPolicy, created.ID, created.Name,
		auditlog.Changes("action", string(created.BlockAction), "lists", fmt.Sprint(len(in.ListIDs))))
	a.Runtime.RequestReload()
	return created, nil
}

// UpdatePolicy saves a policy.
func (a *App) UpdatePolicy(ctx context.Context, actor auditlog.Actor, id int64, in PolicyInput) (models.Policy, error) {
	existing, err := a.Policy(ctx, id)
	if err != nil {
		return models.Policy{}, err
	}
	p, err := a.normalisePolicy(in, existing)
	if err != nil {
		return models.Policy{}, err
	}
	p.ID = id
	updated, err := a.DB.UpdatePolicy(ctx, p, in.ListIDs)
	if err != nil {
		return models.Policy{}, translate(err, fmt.Sprintf("Policy %d was not found.", id),
			fmt.Sprintf("A policy named %q already exists.", p.Name))
	}
	a.Audit.RecordID(ctx, actor, "policy.update", auditlog.ObjectPolicy, id, updated.Name,
		auditlog.Changes("action", string(updated.BlockAction), "lists", fmt.Sprint(len(in.ListIDs))))
	a.Runtime.RequestReload()
	return updated, nil
}

// SetPolicyEnabled toggles a policy.
func (a *App) SetPolicyEnabled(ctx context.Context, actor auditlog.Actor, id int64, enabled bool) error {
	p, err := a.Policy(ctx, id)
	if err != nil {
		return err
	}
	if err := a.DB.SetPolicyEnabled(ctx, id, enabled); err != nil {
		return translate(err, fmt.Sprintf("Policy %d was not found.", id), "")
	}
	action := "policy.disable"
	if enabled {
		action = "policy.enable"
	}
	a.Audit.RecordID(ctx, actor, action, auditlog.ObjectPolicy, id, p.Name, "")
	a.Runtime.RequestReload()
	return nil
}

// DeletePolicy removes a policy.
func (a *App) DeletePolicy(ctx context.Context, actor auditlog.Actor, id int64) error {
	p, err := a.Policy(ctx, id)
	if err != nil {
		return err
	}
	if err := a.DB.DeletePolicy(ctx, id); err != nil {
		return translate(err, fmt.Sprintf("Policy %d was not found.", id), "")
	}
	a.Audit.RecordID(ctx, actor, "policy.delete", auditlog.ObjectPolicy, id, p.Name, "")
	a.Runtime.RequestReload()
	return nil
}

// --- Domain lists -------------------------------------------------------

// ListInput is the editable surface of a blacklist or allowlist.
type ListInput struct {
	Kind        string `json:"kind"`
	Name        string `json:"name"`
	Description string `json:"description"`
	Enabled     *bool  `json:"enabled"`
	SourceURL   string `json:"source_url"`
}

// DomainLists returns blacklists, allowlists, or both when kind is empty.
func (a *App) DomainLists(ctx context.Context, kind, search string) ([]models.DomainList, error) {
	lists, err := a.DB.DomainLists(ctx, kind, search)
	if err != nil {
		return nil, Internal(err, "The list could not be loaded.")
	}
	return lists, nil
}

// DomainList loads one list.
func (a *App) DomainList(ctx context.Context, id int64) (models.DomainList, error) {
	l, err := a.DB.DomainList(ctx, id)
	if errors.Is(err, database.ErrNotFound) {
		return l, NotFound("List %d was not found.", id)
	}
	if err != nil {
		return l, Internal(err, "The list could not be loaded.")
	}
	return l, nil
}

// CreateDomainList stores a blacklist or allowlist.
func (a *App) CreateDomainList(ctx context.Context, actor auditlog.Actor, in ListInput) (models.DomainList, error) {
	kind := strings.ToLower(strings.TrimSpace(in.Kind))
	if kind != models.KindBlacklist && kind != models.KindAllowlist {
		return models.DomainList{}, Invalid("List kind must be blacklist or allowlist.")
	}
	name := strings.TrimSpace(in.Name)
	if name == "" {
		return models.DomainList{}, Invalid("A list name is required.")
	}
	enabled := true
	if in.Enabled != nil {
		enabled = *in.Enabled
	}
	l := models.DomainList{
		Kind:        kind,
		Name:        name,
		Description: strings.TrimSpace(in.Description),
		Enabled:     enabled,
		SourceURL:   strings.TrimSpace(in.SourceURL),
	}
	created, err := a.DB.CreateDomainList(ctx, l)
	if err != nil {
		return models.DomainList{}, translate(err, "List not found.",
			fmt.Sprintf("A %s named %q already exists.", kind, name))
	}
	a.Audit.RecordID(ctx, actor, "list.create", auditlog.ObjectList, created.ID, created.Name,
		auditlog.Changes("kind", created.Kind))
	a.Runtime.RequestReload()
	return created, nil
}

// UpdateDomainList saves list metadata.
func (a *App) UpdateDomainList(ctx context.Context, actor auditlog.Actor, id int64, in ListInput) (models.DomainList, error) {
	existing, err := a.DomainList(ctx, id)
	if err != nil {
		return models.DomainList{}, err
	}
	if name := strings.TrimSpace(in.Name); name != "" {
		existing.Name = name
	}
	existing.Description = strings.TrimSpace(in.Description)
	existing.SourceURL = strings.TrimSpace(in.SourceURL)
	if in.Enabled != nil {
		existing.Enabled = *in.Enabled
	}

	updated, err := a.DB.UpdateDomainList(ctx, existing)
	if err != nil {
		return models.DomainList{}, translate(err, fmt.Sprintf("List %d was not found.", id),
			fmt.Sprintf("A list named %q already exists.", existing.Name))
	}
	a.Audit.RecordID(ctx, actor, "list.update", auditlog.ObjectList, id, updated.Name, "")
	a.Runtime.RequestReload()
	return updated, nil
}

// SetDomainListEnabled toggles a list.
func (a *App) SetDomainListEnabled(ctx context.Context, actor auditlog.Actor, id int64, enabled bool) error {
	l, err := a.DomainList(ctx, id)
	if err != nil {
		return err
	}
	if err := a.DB.SetDomainListEnabled(ctx, id, enabled); err != nil {
		return translate(err, fmt.Sprintf("List %d was not found.", id), "")
	}
	action := "list.disable"
	if enabled {
		action = "list.enable"
	}
	a.Audit.RecordID(ctx, actor, action, auditlog.ObjectList, id, l.Name, "")
	a.Runtime.RequestReload()
	return nil
}

// DeleteDomainList removes a list and every domain in it.
func (a *App) DeleteDomainList(ctx context.Context, actor auditlog.Actor, id int64) error {
	l, err := a.DomainList(ctx, id)
	if err != nil {
		return err
	}
	if err := a.DB.DeleteDomainList(ctx, id); err != nil {
		return translate(err, fmt.Sprintf("List %d was not found.", id), "")
	}
	a.Audit.RecordID(ctx, actor, "list.delete", auditlog.ObjectList, id, l.Name,
		auditlog.Changes("domains", fmt.Sprint(l.DomainCount)))
	a.Runtime.RequestReload()
	return nil
}

// --- Domain entries -----------------------------------------------------

// DomainEntries pages through a list's domains.
func (a *App) DomainEntries(ctx context.Context, listID int64, search string, limit, offset int) ([]models.DomainEntry, int, error) {
	entries, total, err := a.DB.DomainEntries(ctx, listID, search, limit, offset)
	if err != nil {
		return nil, 0, Internal(err, "The domains could not be loaded.")
	}
	return entries, total, nil
}

// AddDomain adds one domain to a list.
func (a *App) AddDomain(ctx context.Context, actor auditlog.Actor, listID int64, domain string, matchSubdomains bool, comment string) (models.DomainEntry, error) {
	l, err := a.DomainList(ctx, listID)
	if err != nil {
		return models.DomainEntry{}, err
	}
	d := strings.TrimSpace(domain)
	if strings.HasPrefix(d, "*.") {
		d = strings.TrimPrefix(d, "*.")
		matchSubdomains = true
	}
	normalised, err := validate.NormaliseDomain(d)
	if err != nil {
		return models.DomainEntry{}, Invalid("%s", err.Error())
	}

	entry, err := a.DB.AddDomain(ctx, models.DomainEntry{
		ListID:          listID,
		Domain:          normalised,
		MatchSubdomains: matchSubdomains,
		Enabled:         true,
		Comment:         strings.TrimSpace(comment),
	})
	if err != nil {
		return models.DomainEntry{}, translate(err, "List not found.",
			fmt.Sprintf("%s is already in %s.", normalised, l.Name))
	}
	a.Audit.RecordID(ctx, actor, "domain.add", auditlog.ObjectDomain, entry.ID, normalised,
		auditlog.Changes("list", l.Name))
	a.Runtime.RequestReload()
	return entry, nil
}

// UpdateDomain saves an existing domain entry.
func (a *App) UpdateDomain(ctx context.Context, actor auditlog.Actor, listID, id int64, domain string, matchSubdomains, enabled bool, comment string) error {
	normalised, err := validate.NormaliseDomain(strings.TrimPrefix(strings.TrimSpace(domain), "*."))
	if err != nil {
		return Invalid("%s", err.Error())
	}
	e := models.DomainEntry{
		ID: id, ListID: listID, Domain: normalised,
		MatchSubdomains: matchSubdomains, Enabled: enabled, Comment: strings.TrimSpace(comment),
	}
	if err := a.DB.UpdateDomain(ctx, e); err != nil {
		return translate(err, fmt.Sprintf("Domain %d was not found.", id),
			fmt.Sprintf("%s is already in this list.", normalised))
	}
	a.Audit.RecordID(ctx, actor, "domain.update", auditlog.ObjectDomain, id, normalised, "")
	a.Runtime.RequestReload()
	return nil
}

// DeleteDomain removes one domain from a list.
func (a *App) DeleteDomain(ctx context.Context, actor auditlog.Actor, id int64) error {
	if err := a.DB.DeleteDomain(ctx, id); err != nil {
		return translate(err, fmt.Sprintf("Domain %d was not found.", id), "")
	}
	a.Audit.RecordID(ctx, actor, "domain.delete", auditlog.ObjectDomain, id, "", "")
	a.Runtime.RequestReload()
	return nil
}

// ClearDomains empties a list.
func (a *App) ClearDomains(ctx context.Context, actor auditlog.Actor, listID int64) (int64, error) {
	l, err := a.DomainList(ctx, listID)
	if err != nil {
		return 0, err
	}
	n, err := a.DB.ClearDomains(ctx, listID)
	if err != nil {
		return 0, Internal(err, "The list could not be cleared.")
	}
	a.Audit.RecordID(ctx, actor, "list.clear", auditlog.ObjectList, listID, l.Name,
		auditlog.Changes("removed", fmt.Sprint(n)))
	a.Runtime.RequestReload()
	return n, nil
}

// ImportDomains parses a domain list and stores it.
//
// Parsing happens fully in memory and the insert runs as a single transaction
// with one prepared statement, so a list of several hundred thousand domains
// is one commit rather than one commit per domain.
func (a *App) ImportDomains(ctx context.Context, actor auditlog.Actor, listID int64,
	r io.Reader, matchSubdomains bool) (models.ImportSummary, error) {

	l, err := a.DomainList(ctx, listID)
	if err != nil {
		return models.ImportSummary{}, err
	}

	parsed, summary := blacklist.Parse(r, blacklist.ParseOptions{DefaultMatchSubdomains: matchSubdomains})
	if len(parsed) == 0 {
		if summary.LinesProcessed == 0 {
			return summary, Invalid("The import was empty.")
		}
		return summary, Invalid("No valid domains were found in %d lines. "+
			"Supported formats are a plain domain list, a hosts file, or Adblock-style ||domain^ rules.",
			summary.LinesProcessed)
	}

	rows := make([]database.ImportDomain, 0, len(parsed))
	for _, p := range parsed {
		rows = append(rows, database.ImportDomain{Domain: p.Domain, MatchSubdomains: p.MatchSubdomains})
	}

	imported, duplicates, err := a.DB.ImportDomains(ctx, listID, rows)
	if err != nil {
		return summary, Internal(err, "The domains could not be imported.")
	}

	// The parser counts duplicates within the file; the database reports
	// domains that were already present. The summary shows the total.
	summary.Imported = imported
	summary.Duplicates += duplicates

	a.Audit.RecordID(ctx, actor, "list.import", auditlog.ObjectList, listID, l.Name,
		auditlog.Changes(
			"imported", fmt.Sprint(summary.Imported),
			"duplicates", fmt.Sprint(summary.Duplicates),
			"invalid", fmt.Sprint(summary.Invalid),
			"lines", fmt.Sprint(summary.LinesProcessed)))
	a.Runtime.RequestReload()
	return summary, nil
}

// ExportDomains writes a list as a plain domain list.
func (a *App) ExportDomains(ctx context.Context, listID int64, w io.Writer) (models.DomainList, error) {
	l, err := a.DomainList(ctx, listID)
	if err != nil {
		return l, err
	}
	fmt.Fprintf(w, "# %s\n", l.Name)
	if l.Description != "" {
		fmt.Fprintf(w, "# %s\n", l.Description)
	}
	fmt.Fprintf(w, "# %d domains exported by VibeDNS\n", l.DomainCount)

	err = a.DB.ExportDomains(ctx, listID, func(domain string, matchSubdomains bool) {
		if matchSubdomains {
			fmt.Fprintln(w, domain)
			return
		}
		// A domain that must match exactly is written in a form the importer
		// will not silently widen.
		fmt.Fprintf(w, "%s # exact\n", domain)
	})
	if err != nil {
		return l, Internal(err, "The domains could not be exported.")
	}
	return l, nil
}

// LookupDomain reports which lists cover a name, for the "why was this
// blocked?" tool.
type LookupHit struct {
	ListID   int64  `json:"list_id"`
	ListName string `json:"list_name"`
	Kind     string `json:"kind"`
	Matched  string `json:"matched_domain"`
}

// LookupDomain checks a name against every compiled list.
func (a *App) LookupDomain(ctx context.Context, name string) ([]LookupHit, error) {
	domain, err := validate.NormaliseDomain(name)
	if err != nil {
		return nil, Invalid("%s", err.Error())
	}
	lists, err := a.DB.DomainLists(ctx, "", "")
	if err != nil {
		return nil, Internal(err, "The lists could not be loaded.")
	}

	sets := a.Snapshot().Policy.Sets()
	var hits []LookupHit
	for _, l := range lists {
		set, ok := sets[l.ID]
		if !ok {
			continue // list is disabled, so it was not compiled
		}
		if matched, found := set.Match(domain); found {
			hits = append(hits, LookupHit{
				ListID: l.ID, ListName: l.Name, Kind: l.Kind, Matched: matched,
			})
		}
	}
	return hits, nil
}