package cabana

import (
	"context"
	"errors"
	"net/http"
	"net/url"
	"regexp"
	"sort"
	"strings"
	"sync"
	"time"
	"unicode/utf8"

	"git.golem15.com/golem15/summercms/modules/bonfire"
	"git.golem15.com/golem15/summercms/modules/bouncer"
	"git.golem15.com/golem15/summercms/modules/compass"
	"git.golem15.com/golem15/summercms/modules/kiosk"
	"git.golem15.com/golem15/summercms/modules/party"
)

// The admin's read-only Plugins screen (Settings → System → Plugins): the
// plugins the application was built with, their versions and, when the
// plugin registry is configured, available updates and a marketplace
// search. The SPA calls only these endpoints; cabana calls the registry.

// PermissionViewPlugins opens the Plugins screen. No role is granted it in
// code: until an administrator grants it, only superusers see the screen.
const PermissionViewPlugins = "backend.view_plugins"

// pluginsSettingsCode is the settings code of the Plugins screen entry and
// pluginsScreenPath the SPA route it opens.
const (
	pluginsSettingsCode = "plugins"
	pluginsScreenPath   = "/system/plugins"
)

// States of the plugin registry on the Plugins screen.
const (
	// registryStatusOK: the registry answered (or is configured and was
	// not needed for this answer).
	registryStatusOK = "ok"
	// registryStatusDisabled: plugins.registry_url is empty; no request
	// leaves the process.
	registryStatusDisabled = "disabled"
	// registryStatusUnavailable: the registry did not answer in time or
	// answered with an error.
	registryStatusUnavailable = "unavailable"
)

// PluginsOverview is the GET /plugins payload: the framework version the
// application was built with, the state of the plugin registry and every
// activated plugin in summer.yaml order.
type PluginsOverview struct {
	Framework string            `json:"framework"`
	Registry  RegistryState     `json:"registry"`
	Plugins   []InstalledPlugin `json:"plugins"`
}

// RegistryState tells the admin whether the plugin registry is configured
// (Enabled, false when plugins.registry_url is empty) and how it answered:
// Status is ok, disabled or unavailable.
type RegistryState struct {
	Enabled bool   `json:"enabled"`
	Status  string `json:"status"`
}

// InstalledPlugin is one activated plugin with the metadata summer build
// baked in (party.Info) and, for a plugin the registry lists, the newest
// release the built framework version allows. Name, Description, Version,
// Source, Module and Package are empty for an application built before
// plugin metadata existed and for a plugin without plugin.yaml (Name and
// Description). Latest is the newest compatible release; UpdateAvailable
// is true when it is newer than the installed version, and UpdateCommand
// is then the summer command that installs it. LatestFramework names the
// framework version a newer, incompatible release needs.
type InstalledPlugin struct {
	ID              string `json:"id"`
	Name            string `json:"name"`
	Description     string `json:"description"`
	Version         string `json:"version"`
	Source          string `json:"source"`
	Module          string `json:"module"`
	Package         string `json:"package"`
	Listed          bool   `json:"listed"`
	Latest          string `json:"latest"`
	LatestFramework string `json:"latestFramework"`
	UpdateAvailable bool   `json:"updateAvailable"`
	UpdateCommand   string `json:"updateCommand"`
}

// MarketplacePlugin is one plugin of the registry's search on the Plugins
// screen: the registry's listing (name, description, category, featured
// flag, https icon URL, newest release and its framework minimum), whether
// the application already has it (Installed), whether the built framework
// satisfies the newest release's minimum (Compatible) and the summer
// command that installs it.
type MarketplacePlugin struct {
	ID              string `json:"id"`
	Name            string `json:"name"`
	Description     string `json:"description"`
	Category        string `json:"category"`
	Featured        bool   `json:"featured"`
	IconURL         string `json:"iconUrl"`
	LatestVersion   string `json:"latestVersion"`
	LatestFramework string `json:"latestFramework"`
	Installed       bool   `json:"installed"`
	Compatible      bool   `json:"compatible"`
	InstallCommand  string `json:"installCommand"`
}

// MarketplaceResponse is the GET /plugins/marketplace answer.
type MarketplaceResponse struct {
	Data []MarketplacePlugin `json:"data"`
	Meta MarketplaceMeta     `json:"meta"`
}

// MarketplaceMeta carries the registry state, the number of plugins in
// data and the registry's categories (sorted) for the category filter.
type MarketplaceMeta struct {
	Registry   RegistryState `json:"registry"`
	Total      int           `json:"total"`
	Categories []string      `json:"categories"`
}

// Limits of the Plugins screen's registry calls (T-34-31): a short
// per-call timeout, an in-process cache that also keeps failures for a
// while, and few concurrent version lookups.
const (
	registryCallTimeout = 4 * time.Second
	marketplaceTTL      = 5 * time.Minute
	versionsTTL         = 15 * time.Minute
	registryFailureTTL  = time.Minute
	registryLookups     = 4
	marketplaceMaxQuery = 100
)

var (
	// marketplaceCategoryRe is the registry's category filter rule.
	marketplaceCategoryRe = regexp.MustCompile(`^[a-z0-9-]{1,40}$`)
	// marketplaceIDRe is the plugin ID shape; IDs end up in a command.
	marketplaceIDRe = regexp.MustCompile(`^[a-z][a-z0-9]*\.[a-z][a-z0-9]*$`)
)

// pluginRegistry is the part of kiosk.Client the Plugins screen uses.
type pluginRegistry interface {
	List(ctx context.Context, q, category string) (kiosk.ListResponse, error)
	Versions(ctx context.Context, id string) ([]kiosk.RegistryVersion, error)
}

// pluginCatalog is the Plugins screen's view of the registry: the client
// built from plugins.registry_url (nil when it is empty or unusable) and
// a TTL cache of searches and per-plugin versions.
type pluginCatalog struct {
	disabled bool
	registry pluginRegistry
	timeout  time.Duration
	now      func() time.Time

	mu       sync.Mutex
	lists    map[string]cachedList
	versions map[string]cachedVersions
}

type cachedList struct {
	resp    kiosk.ListResponse
	err     error
	expires time.Time
}

type cachedVersions struct {
	versions []kiosk.RegistryVersion
	listed   bool
	err      error
	expires  time.Time
}

// newPluginCatalog builds the catalog for cfg. An empty registry URL
// disables it; a URL kiosk refuses leaves it enabled with no client, so
// every lookup reports the registry unavailable.
func newPluginCatalog(cfg *compass.Config) *pluginCatalog {
	c := &pluginCatalog{
		timeout:  registryCallTimeout,
		now:      time.Now,
		lists:    map[string]cachedList{},
		versions: map[string]cachedVersions{},
	}
	base := kiosk.RegistryURL(cfg)
	if base == "" {
		c.disabled = true
		return c
	}
	if client, err := kiosk.NewClient(base, cfg); err == nil {
		c.registry = client
	}
	return c
}

// pluginCatalog returns the catalog Activate built. A service assembled
// without Activate gets a fresh, uncached one per call.
func (s *service) pluginCatalog() *pluginCatalog {
	if s.catalog != nil {
		return s.catalog
	}
	return newPluginCatalog(s.config())
}

func (c *pluginCatalog) enabled() bool { return !c.disabled }

// state is the registry state before any call: disabled or ok.
func (c *pluginCatalog) state() RegistryState {
	if c.disabled {
		return RegistryState{Enabled: false, Status: registryStatusDisabled}
	}
	return RegistryState{Enabled: true, Status: registryStatusOK}
}

var errRegistryUnusable = errors.New("cabana: plugins.registry_url is not a usable registry URL")

// callContext detaches a registry call from the request's cancellation,
// so a closed browser tab does not cache a failure, and bounds it with
// the catalog's timeout.
func (c *pluginCatalog) callContext(ctx context.Context) (context.Context, context.CancelFunc) {
	return context.WithTimeout(context.WithoutCancel(ctx), c.timeout)
}

// list returns the registry's search for q and category, cached.
func (c *pluginCatalog) list(ctx context.Context, q, category string) (kiosk.ListResponse, error) {
	key := q + "\x00" + category
	c.mu.Lock()
	if hit, ok := c.lists[key]; ok && c.now().Before(hit.expires) {
		c.mu.Unlock()
		return hit.resp, hit.err
	}
	c.mu.Unlock()
	var (
		resp kiosk.ListResponse
		err  = errRegistryUnusable
	)
	if c.registry != nil {
		callCtx, cancel := c.callContext(ctx)
		resp, err = c.registry.List(callCtx, q, category)
		cancel()
	}
	ttl := marketplaceTTL
	if err != nil {
		resp, ttl = kiosk.ListResponse{}, registryFailureTTL
	}
	c.mu.Lock()
	c.lists[key] = cachedList{resp: resp, err: err, expires: c.now().Add(ttl)}
	c.mu.Unlock()
	return resp, err
}

// releases returns the releases of plugin id, cached. listed is false when
// the registry does not know the ID (a 404 is an answer, not a failure).
func (c *pluginCatalog) releases(ctx context.Context, id string) ([]kiosk.RegistryVersion, bool, error) {
	c.mu.Lock()
	if hit, ok := c.versions[id]; ok && c.now().Before(hit.expires) {
		c.mu.Unlock()
		return hit.versions, hit.listed, hit.err
	}
	c.mu.Unlock()
	var (
		versions []kiosk.RegistryVersion
		listed   bool
		err      = errRegistryUnusable
	)
	if c.registry != nil {
		callCtx, cancel := c.callContext(ctx)
		versions, err = c.registry.Versions(callCtx, id)
		cancel()
		listed = err == nil
		if errors.Is(err, kiosk.ErrNotFound) {
			err = nil
		}
	}
	ttl := versionsTTL
	if err != nil {
		versions, ttl = nil, registryFailureTTL
	}
	c.mu.Lock()
	c.versions[id] = cachedVersions{versions: versions, listed: listed, err: err, expires: c.now().Add(ttl)}
	c.mu.Unlock()
	return versions, listed, err
}

// applyUpdates fills the registry fields of every plugin that has a
// version, at most registryLookups lookups at a time, and reports false
// when any lookup failed.
func (c *pluginCatalog) applyUpdates(ctx context.Context, overview *PluginsOverview) bool {
	framework := frameworkRelease(overview.Framework)
	var (
		wg     sync.WaitGroup
		mu     sync.Mutex
		failed bool
	)
	slots := make(chan struct{}, registryLookups)
	for i := range overview.Plugins {
		plugin := &overview.Plugins[i]
		if plugin.Version == "" || plugin.Source == party.SourceLocal || !marketplaceIDRe.MatchString(plugin.ID) {
			continue
		}
		wg.Add(1)
		slots <- struct{}{}
		go func() {
			defer wg.Done()
			defer func() { <-slots }()
			versions, listed, err := c.releases(ctx, plugin.ID)
			if err != nil {
				mu.Lock()
				failed = true
				mu.Unlock()
				return
			}
			if listed {
				applyUpdate(plugin, versions, framework)
			}
		}()
	}
	wg.Wait()
	return !failed
}

// applyUpdate sets the registry fields of a listed plugin: Latest is the
// newest release framework allows, an update is available when Latest is
// newer than the installed version's base tag, and LatestFramework names
// the minimum of a newer release that framework does not satisfy. The rule
// is summer plugin:update's.
func applyUpdate(plugin *InstalledPlugin, versions []kiosk.RegistryVersion, framework string) {
	plugin.Listed = true
	latest, compatible := kiosk.NewestCompatible(versions, framework)
	if compatible {
		plugin.Latest = latest.Version
	}
	base := kiosk.BaseVersion(plugin.Version)
	if compatible && base != "" && kiosk.CompareVersions(latest.Version, base) > 0 {
		plugin.UpdateAvailable = true
		plugin.UpdateCommand = "summer plugin:update " + plugin.ID
	}
	var newest kiosk.RegistryVersion
	for _, v := range versions {
		if kiosk.ValidVersion(v.Version) && (newest.Version == "" || kiosk.CompareVersions(v.Version, newest.Version) > 0) {
			newest = v
		}
	}
	if newest.Version == "" || (compatible && kiosk.CompareVersions(newest.Version, latest.Version) <= 0) {
		return
	}
	if base != "" && kiosk.CompareVersions(newest.Version, base) <= 0 {
		return
	}
	plugin.LatestFramework = newest.Framework
}

// pluginsSettingsEntry is the Settings → System link to the Plugins
// screen. It opens an SPA route, not an admin controller.
func pluginsSettingsEntry(label, description, category string) SettingsEntry {
	return SettingsEntry{
		Code: pluginsSettingsCode, Label: label, Description: description,
		Category: category, Icon: "puzzle", Order: 120, Keywords: []string{},
		Path: pluginsScreenPath,
	}
}

// pluginsPrincipal answers 401 without a backend principal and 403 when
// the principal may not open the Plugins screen; ok is false after either.
func pluginsPrincipal(w http.ResponseWriter, r *http.Request) (*bouncer.Principal, bool) {
	principal, ok := bouncer.User(r.Context())
	if !ok || principal == nil || !principal.Backend {
		WriteError(w, http.StatusUnauthorized, "unauthenticated", msgUnauthenticated)
		return nil, false
	}
	if !Allows(principal, []string{PermissionViewPlugins}) {
		WriteError(w, http.StatusForbidden, "forbidden", msgForbidden)
		return nil, false
	}
	return principal, true
}

// pluginsInstalled answers GET /plugins. With the registry configured,
// each plugin that has a version is looked up (cached, at most
// registryLookups at a time); a registry that fails leaves the list intact
// and reports the registry unavailable.
func (s *service) pluginsInstalled(w http.ResponseWriter, r *http.Request) {
	if _, ok := pluginsPrincipal(w, r); !ok {
		return
	}
	overview := s.installedPlugins()
	catalog := s.pluginCatalog()
	overview.Registry = catalog.state()
	if catalog.enabled() && !catalog.applyUpdates(r.Context(), &overview) {
		overview.Registry.Status = registryStatusUnavailable
	}
	WriteData(w, http.StatusOK, overview, nil)
}

// pluginsMarketplace answers GET /plugins/marketplace?q=&category=: the
// registry's search, with the plugins the application already has and the
// ones the built framework is too old for marked, and the command that
// installs each. q and category follow the registry's own rules (400
// otherwise). A disabled or failing registry answers an empty list.
func (s *service) pluginsMarketplace(w http.ResponseWriter, r *http.Request) {
	if _, ok := pluginsPrincipal(w, r); !ok {
		return
	}
	query := r.URL.Query()
	q := strings.TrimSpace(query.Get("q"))
	category := query.Get("category")
	if utf8.RuneCountInString(q) > marketplaceMaxQuery {
		WriteErrorDetails(w, http.StatusBadRequest, "invalid_query", "Invalid query", map[string]any{"q": []string{"The search may have at most 100 characters."}})
		return
	}
	if category != "" && !marketplaceCategoryRe.MatchString(category) {
		WriteErrorDetails(w, http.StatusBadRequest, "invalid_query", "Invalid query", map[string]any{"category": []string{"The category must match ^[a-z0-9-]{1,40}$."}})
		return
	}
	catalog := s.pluginCatalog()
	out := MarketplaceResponse{Data: []MarketplacePlugin{}, Meta: MarketplaceMeta{Registry: catalog.state(), Categories: []string{}}}
	if !catalog.enabled() {
		writeJSON(w, http.StatusOK, out)
		return
	}
	list, err := catalog.list(r.Context(), q, category)
	if err != nil {
		out.Meta.Registry.Status = registryStatusUnavailable
		writeJSON(w, http.StatusOK, out)
		return
	}
	overview := s.installedPlugins()
	installed := make(map[string]bool, len(overview.Plugins))
	for _, p := range overview.Plugins {
		installed[p.ID] = true
	}
	framework := frameworkRelease(overview.Framework)
	for _, p := range list.Data {
		if !marketplaceIDRe.MatchString(p.ID) {
			// The ID ends up in a shell command; never offer an odd one.
			continue
		}
		out.Data = append(out.Data, MarketplacePlugin{
			ID: p.ID, Name: p.Name, Description: p.Description, Category: p.Category,
			Featured: p.Featured, IconURL: httpsURL(p.IconURL),
			LatestVersion: p.LatestVersion, LatestFramework: p.LatestFramework,
			Installed:      installed[p.ID],
			Compatible:     kiosk.Satisfies(framework, p.LatestFramework),
			InstallCommand: "summer plugin:install " + p.ID,
		})
	}
	out.Meta.Total = len(out.Data)
	if q == "" && category == "" {
		out.Meta.Categories = categoriesOf(list.Data)
	} else if all, err := catalog.list(r.Context(), "", ""); err == nil {
		out.Meta.Categories = categoriesOf(all.Data)
	}
	writeJSON(w, http.StatusOK, out)
}

// categoriesOf returns the distinct valid categories of the plugins the
// marketplace offers (valid IDs only), sorted.
func categoriesOf(plugins []kiosk.RegistryPlugin) []string {
	seen := map[string]bool{}
	out := []string{}
	for _, p := range plugins {
		if !marketplaceIDRe.MatchString(p.ID) {
			continue
		}
		if p.Category != "" && marketplaceCategoryRe.MatchString(p.Category) && !seen[p.Category] {
			seen[p.Category] = true
			out = append(out, p.Category)
		}
	}
	sort.Strings(out)
	return out
}

// httpsURL returns raw when it is an absolute https URL and "" otherwise,
// so the admin never loads an icon over another scheme.
func httpsURL(raw string) string {
	u, err := url.Parse(raw)
	if err != nil || u.Scheme != "https" || u.Host == "" || u.User != nil {
		return ""
	}
	return raw
}

// frameworkRelease is the release a framework version string stands for:
// the base tag of a git describe string, the string itself otherwise
// ("devel" satisfies only releases without a framework minimum).
func frameworkRelease(framework string) string {
	if base := kiosk.BaseVersion(framework); base != "" {
		return base
	}
	return framework
}

// installedPlugins lists the activated plugins from the metadata summer
// build published (party.Installed). An application built before that
// metadata existed lists the IDs of party.Activated instead, and its
// framework version comes from the binary's build information.
func (s *service) installedPlugins() PluginsOverview {
	overview := PluginsOverview{Plugins: []InstalledPlugin{}}
	if s == nil || s.app == nil {
		overview.Framework = bonfire.BuildVersion().Framework
		return overview
	}
	if installed, ok := s.app.Lookup[party.Installed](); ok {
		overview.Framework = installed.Framework
		for _, info := range installed.Plugins {
			overview.Plugins = append(overview.Plugins, InstalledPlugin{
				ID: info.ID, Name: info.Name, Description: info.Description,
				Version: info.Version, Source: info.Source,
				Module: info.Module, Package: info.Package,
			})
		}
	} else if activated, ok := s.app.Lookup[party.Activated](); ok {
		for _, plugin := range activated {
			if plugin == nil || plugin.ID() == backendScreensPluginID {
				continue
			}
			overview.Plugins = append(overview.Plugins, InstalledPlugin{ID: plugin.ID()})
		}
	}
	if overview.Framework == "" {
		overview.Framework = bonfire.BuildVersion().Framework
	}
	return overview
}