// Package ankersolix is a built-in connector for the Anker Power / Solix cloud,
// scoped to the Anker Solix V1 Smart EV Charger (product A5191). It is a Go
// re-implementation of the authentication and read-only data flow from the
// anker-solix-api project (https://github.com/thomluther/anker-solix-api),
// adapted to DriverVault's plugin contract. It tracks upstream v3.8.1
// (ha-anker-solix 3.8.1); the login exchange and every endpoint used here are
// unchanged since v3.7.0.
//
// Scope & limitations:
//   - Read-only. Only EV-charger information is retrieved; no charge start/stop
//     or configuration commands are implemented. Control is a separate concern
//     and runs over OCPP (see internal/ocpp), not the cloud API.
//   - Cloud only. Upstream reads a charger's live state over both the cloud and
//     MQTT; we take the cloud half. Signals that exist only in MQTT — the boost
//     flag and the plug/start countdowns — are therefore never set, which the
//     derived state accounts for.
//   - Single device family. Capabilities target the V1 Smart EV Charger; other
//     Anker Power devices (solarbanks, power stations, HES) are out of scope.
//   - Unofficial. This talks to Anker's private mobile-app cloud API with the
//     app's public client identity; Anker may change or break it at any time.
//
// Authentication is a single login exchange, not OAuth:
//  1. An ephemeral ECDH key pair (NIST P-256 / SECP256R1) is generated and a
//     shared secret is derived against Anker's static server public key.
//  2. The account password is AES-256-CBC encrypted under that shared secret
//     (key = secret, IV = first 16 bytes of the secret, PKCS#7 padding) and
//     base64-encoded.
//  3. POST passport/login with the client public key and encrypted password
//     returns an auth_token (valid ~7 days), a user_id and an expiry. All
//     subsequent requests send x-auth-token plus gtoken = md5(user_id).
//
// The auth token is long-lived; when it nears expiry (or a request is rejected
// as unauthorized) the plugin performs a fresh login. There is no refresh token.
package ankersolix

import (
	"bytes"
	"context"
	"crypto/aes"
	"crypto/cipher"
	"crypto/ecdh"
	"crypto/md5"
	"crypto/rand"
	"encoding/base64"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"sort"
	"strings"
	"sync"
	"time"

	"drivervault/apiserver/internal/plugins"
)

// Anker cloud servers. Country assignment decides which one an account lives on;
// a wrong assignment authenticates but returns no sites/devices. Countries in
// comCountries use the global server, everything else defaults to EU (mirroring
// anker-solix-api's API_SERVERS / API_COUNTRIES).
const (
	serverEU  = "https://ankerpower-api-eu.anker.com"
	serverCOM = "https://ankerpower-api.anker.com"

	// serverPublicKeyHex is Anker's static server public key (uncompressed P-256
	// point, 0x04 || X || Y). Identical for the EU and global servers. This is an
	// app constant, not a user secret.
	serverPublicKeyHex = "04c5c00c4f8d1197cc7c3167c52bf7acb054d722f0ef08dcd7e0883236e0d72a3868d9750cb47fa4619248f3d83f0f662671dadc6e2d31c2f41db0161651c7c076"
)

// Endpoints. Login plus the read-only endpoints relevant to an EV charger.
const (
	epLogin = "passport/login"

	epStandaloneChargers = "charging_hes_svc/get_user_bind_and_not_in_station_evchargers" // list account EV chargers not assigned to a station
	epStationInfo        = "charging_hes_svc/get_evcharger_station_info"                  // per-charger station/status info
	epSystemRunInfo      = "charging_hes_svc/get_system_running_info"                     // system runtime info; carries evChargerInfos[].evChargerStatus
	epSceneInfo          = "power_service/v1/site/get_scen_info"                          // site home view; carries charging_pile_info (note upstream's "scen" typo)
	epEnergyAnalysis     = "power_service/v1/site/energy_analysis"                        // interval energy for a site, device_type "ev_charger"
	epChargeStats        = "power_service/v1/app/order/get_charge_order_stats"            // charging totals for a charger
	epChargeStatsList    = "power_service/v1/app/order/get_charge_order_stats_list"       // per-order charging history
	epOcppInfo           = "power_service/v1/app/get_ocpp_info"                           // OCPP endpoint source info for a charger
	epOcppEndpoints      = "power_service/v1/app/get_ocpp_endpoint_list"                  // the OCPP endpoints Anker itself uses, with their source numbers
	epRfidCards          = "power_service/v1/rfid/get_device_cards"                       // RFID cards authorised on a charger
	epBindDevices        = "power_service/v1/app/get_relate_and_bind_devices"             // bound devices incl. firmware version
	epSiteList           = "power_service/v1/site/get_site_list"                          // sites (systems) on the account
	epUserVehicles       = "power_service/v1/app/vehicle/get_vehicle_list"                // vehicles registered for smart charging
	epVehicleDetail      = "power_service/v1/app/vehicle/get_vehicle_detail"              // details for one registered vehicle
)

// EV-charger operating states, mirroring anker-solix-api's SolixEvChargerStatus.
// The cloud reports the same code under two names: operating_state in a site's
// charging_pile_list, evChargerStatus in HES system running info.
const (
	stateStandby       = "standby"
	statePreparing     = "preparing"
	stateCharging      = "charging"
	stateChargerPaused = "charger_paused"
	stateVehiclePaused = "vehicle_paused"
	stateCompleted     = "completed"
	stateReserving     = "reserving"
	stateDisabled      = "disabled"
	stateError         = "error"
	stateUnknown       = "unknown"
)

var evChargerStatus = map[int]string{
	0: stateStandby, 1: statePreparing, 2: stateCharging, 3: stateChargerPaused,
	4: stateVehiclePaused, 5: stateCompleted, 6: stateReserving, 7: stateDisabled,
	8: stateError,
}

// Operational modes, mirroring SolixEvChargerMode. start/stop/skip/boost are the
// four real control values; wait_plug and wait_start are virtual states the
// charger passes through and cannot be commanded into.
const (
	modeStartCharge = "start_charge"
	modeStopCharge  = "stop_charge"
	modeSkipDelay   = "skip_delay"
	modeBoostCharge = "boost_charge"
	modeWaitStart   = "wait_start"
	modeWaitPlug    = "wait_plug"
)

// ocppConnStatus decodes ocpp_connect_status (SolixOcppConnectionStatus).
var ocppConnStatus = map[int]string{0: "disconnected", 1: "connecting", 2: "connected"}

// tokenExpiryMargin is subtracted from the reported token lifetime so a request
// never fires with a token that expires mid-flight.
const tokenExpiryMargin = 5 * time.Minute

// comCountries are the ISO country IDs served by the global (".com") server.
// Any country not listed here is served by the EU server.
var comCountries = map[string]bool{
	"DZ": true, "LB": true, "SY": true, "EG": true, "LY": true, "TN": true,
	"MA": true, "JO": true, "PS": true, "AR": true, "AU": true, "BR": true,
	"HK": true, "IN": true, "MX": true, "NG": true, "NZ": true, "RU": true,
	"SG": true, "ZA": true, "KR": true, "TW": true, "US": true, "CA": true,
}

func init() {
	plugins.Register("anker-solix", func() plugins.Plugin { return &Plugin{} })
}

// tokenInfo holds the currently-held auth token and derived values.
type tokenInfo struct {
	authToken  string
	gtoken     string // md5(user_id)
	nickname   string
	expiration time.Time
}

// Plugin is the Anker Solix EV-charger connector.
type Plugin struct {
	email     string
	password  string
	countryId string

	mu      sync.Mutex // guards the fields above and the client
	apiBase string
	client  *http.Client

	// sess holds the token and the login backoff, shared by every instance
	// configured for the same account (see session.go). It is what stops the
	// manager's per-request instances from signing in once each.
	sess *session
}

// Descriptor returns the plugin's static metadata for the admin panel.
func (p *Plugin) Descriptor() plugins.Descriptor {
	return plugins.Descriptor{
		Name:     "anker-solix",
		Provider: "Anker Solix (V1 Smart EV Charger)",
		Version:  "0.2.0",
		Kind:     plugins.KindBuiltin,
		Category: plugins.CategoryChargers,
		AuthType: plugins.AuthBasic,
		Capabilities: []plugins.Capability{
			{ID: "chargers", Method: "POST", Endpoint: epStandaloneChargers, Description: "Every EV charger on the account, merged from the standalone, per-site and bound-device views (see chargers.go)."},
			{ID: "charger-status", Method: "POST", Endpoint: epStationInfo, Description: "Live station/status info for one charger (needs sn; optional featuretype 1 or 2)."},
			{ID: "charger-state", Method: "POST", Endpoint: epSceneInfo, Description: "Normalized live state of a site's EV chargers: status, operational mode and the modes it can be switched to (needs siteId; optional sn)."},
			{ID: "site-status", Method: "POST", Endpoint: epSceneInfo, Description: "Live site view; EV chargers appear under charging_pile_info (needs siteId)."},
			{ID: "charge-stats", Method: "POST", Endpoint: epChargeStats, Description: "Cumulative charging statistics for one charger (needs sn)."},
			{ID: "charge-orders", Method: "POST", Endpoint: epChargeStatsList, Description: "Per-session charging history for one charger (needs sn)."},
			{ID: "charge-energy", Method: "POST", Endpoint: epEnergyAnalysis, Description: "Interval charging energy for a site's EV charger (needs siteId; optional sn, range, startDate, endDate)."},
			{ID: "rfid-cards", Method: "POST", Endpoint: epRfidCards, Description: "RFID cards authorised on one charger (needs sn)."},
			{ID: "ocpp-info", Method: "POST", Endpoint: epOcppInfo, Description: "OCPP endpoint source info for one charger (needs sn)."},
			{ID: "ocpp-endpoints", Method: "POST", Endpoint: epOcppEndpoints, Description: "The OCPP endpoints Anker itself uses, with their source numbers."},
			{ID: "devices", Method: "POST", Endpoint: epBindDevices, Description: "Bound devices on the account, incl. firmware version."},
			{ID: "sites", Method: "POST", Endpoint: epSiteList, Description: "Sites (systems) registered to the account."},
			{ID: "vehicles", Method: "POST", Endpoint: epUserVehicles, Description: "Vehicles registered for smart charging."},
			{ID: "vehicle", Method: "POST", Endpoint: epVehicleDetail, Description: "Details for one registered vehicle (needs vehicleId)."},
		},
		ConfigFields: []plugins.ConfigField{
			// Credentials are intentionally NOT required at the global (panel) layer,
			// matching the Toyota connector: an operator may set a shared account
			// here, or leave it blank for a future per-user cascade. The plugin
			// returns a clear error when a request is made without credentials.
			{Key: "email", Label: "Anker account email", Type: "text",
				Help: "The email address for your Anker / Solix (mobile app) account."},
			{Key: "password", Label: "Anker account password", Type: "password", Secret: true,
				Help: "Your Anker account password. Stored locally, sent only (encrypted) to Anker's login endpoint."},
			{Key: "country", Label: "Country", Type: "text", Default: "DE",
				Help: "ISO country code of your Anker account (e.g. DE, GB, US). Determines which Anker server the account lives on; a wrong value logs in but shows no devices."},
			// controlMode selects the OCPP control path. It does not affect this
			// (read-only) cloud plugin — the CSMS that acts on it lives in the api
			// package (internal/ocpp) — but it is advertised here so a superadmin can
			// set/lock it at the global layer, and it cascades like the other fields.
			{Key: "controlMode", Label: "Control mode", Type: "select", Default: "off",
				Help: "How DriverVault controls the charger over OCPP. Off = monitoring only (default). Own CSMS = the charger connects directly to DriverVault. Proxy CSMS = DriverVault relays to Anker's cloud and can inject commands.",
				Options: []plugins.SelectOption{
					{Value: "off", Label: "Off (monitoring only)"},
					{Value: "own", Label: "Own CSMS (full control)"},
					{Value: "proxy", Label: "Proxy CSMS (relay + control)"},
				}},
		},
	}
}

// Init applies resolved config and builds the HTTP client. It performs no
// network I/O; login happens lazily on the first request or health check.
func (p *Plugin) Init(_ context.Context, config map[string]string) error {
	p.mu.Lock()
	defer p.mu.Unlock()

	p.email = strings.TrimSpace(config["email"])
	p.password = config["password"]
	p.countryId = strings.ToUpper(strings.TrimSpace(config["country"]))
	if p.countryId == "" {
		p.countryId = "DE"
	}
	if comCountries[p.countryId] {
		p.apiBase = serverCOM
	} else {
		p.apiBase = serverEU
	}
	// Credentials pick the session, so re-configuring the same account keeps its
	// token and its backoff, and changing account or country starts a fresh one.
	p.sess = sessionFor(p.apiBase, p.email, p.password)
	p.client = &http.Client{Timeout: 30 * time.Second}
	return nil
}

// HealthCheck logs in (if needed) and counts the account's EV chargers. It takes
// the same inventory the chargers capability returns rather than the standalone
// list alone: that list omits every charger that belongs to a system, so probing
// it reported "0 chargers" for an account whose chargers the panel was, at the
// same moment, listing.
//
// Authenticated but holding no charger is degraded, not down — the half we
// address works, and the missing half is the account (or the country, which
// picks the regional server).
func (p *Plugin) HealthCheck(ctx context.Context) plugins.Health {
	start := time.Now()
	doc, err := p.chargerInventory(ctx)
	lat := time.Since(start).Milliseconds()
	if err != nil {
		return plugins.Health{Status: plugins.StatusDown, LatencyMs: lat, Detail: shorten(err.Error())}
	}
	if doc.Count == 0 {
		detail := "authenticated; no EV charger on the account — if it does own one, check the country setting, which picks the Anker server"
		if len(doc.Warnings) > 0 {
			detail = "authenticated; no EV charger found: " + strings.Join(doc.Warnings, "; ")
		}
		return plugins.Health{Status: plugins.StatusDegraded, LatencyMs: lat, Detail: shorten(detail)}
	}
	detail := fmt.Sprintf("authenticated; %d EV charger(s) on the account", doc.Count)
	if len(doc.Warnings) > 0 {
		// Some view failed; the count still stands, but say it is a floor.
		detail += fmt.Sprintf(" (%d of the cloud's views did not answer)", len(doc.Warnings))
	}
	return plugins.Health{Status: plugins.StatusOK, LatencyMs: lat, Detail: detail}
}

// invokeParams is the union of everything an action may be given. Per-charger
// actions take "sn" (the charger serial); per-site actions take "siteId", which
// comes from the "sites" capability.
type invokeParams struct {
	SN          string `json:"sn"`
	SiteID      string `json:"siteId"`
	VehicleID   string `json:"vehicleId"`
	FeatureType int    `json:"featuretype"`
	Range       string `json:"range"`     // day | week | month | year
	StartDate   string `json:"startDate"` // YYYY-MM-DD, or YYYY-MM / YYYY for month / year
	EndDate     string `json:"endDate"`
}

// Invoke runs a named read-only capability. The upstream response body is
// returned verbatim, except for "charger-state", which is derived (see
// chargerState).
func (p *Plugin) Invoke(ctx context.Context, action string, params json.RawMessage) (json.RawMessage, error) {
	var pp invokeParams
	if len(params) > 0 {
		if err := json.Unmarshal(params, &pp); err != nil {
			return nil, fmt.Errorf("anker-solix: invalid params: %w", err)
		}
	}
	pp.SN = strings.TrimSpace(pp.SN)
	pp.SiteID = strings.TrimSpace(pp.SiteID)
	pp.VehicleID = strings.TrimSpace(pp.VehicleID)

	// chargers and charger-state both fan out over several endpoints and return
	// a derived document, so they do not fit the single-endpoint dispatch below.
	if action == "chargers" {
		return p.accountChargers(ctx)
	}
	if action == "charger-state" {
		if pp.SiteID == "" {
			return nil, fmt.Errorf("anker-solix: action %q requires a siteId", action)
		}
		return p.chargerState(ctx, pp.SiteID, pp.SN)
	}

	var (
		endpoint string
		payload  map[string]any
		needSN   bool
		needSite bool
	)
	switch action {
	case "devices":
		endpoint, payload = epBindDevices, map[string]any{}
	case "sites":
		endpoint, payload = epSiteList, map[string]any{}
	case "vehicles":
		endpoint, payload = epUserVehicles, map[string]any{}
	case "ocpp-endpoints":
		endpoint, payload = epOcppEndpoints, map[string]any{}
	case "charger-status":
		// featuretype selects which slice of the station record is returned;
		// Anker accepts 1 and 2, and 1 is what the app asks for by default.
		ft := pp.FeatureType
		if ft != 1 && ft != 2 {
			ft = 1
		}
		endpoint, needSN = epStationInfo, true
		payload = map[string]any{"evChargerSn": pp.SN, "featuretype": ft}
	case "charge-stats":
		endpoint, needSN = epChargeStats, true
		payload = map[string]any{"device_sn": pp.SN, "date_type": "all", "start_date": "", "end_date": ""}
	case "charge-orders":
		endpoint, needSN = epChargeStatsList, true
		payload = map[string]any{"device_sn": pp.SN, "order_status": 1, "date_type": "all",
			"start_date": "", "end_date": "", "page": 0, "page_size": 10}
	case "rfid-cards":
		endpoint, needSN = epRfidCards, true
		payload = map[string]any{"device_sn": pp.SN}
	case "ocpp-info":
		endpoint, needSN = epOcppInfo, true
		payload = map[string]any{"device_sn": pp.SN}
	case "site-status":
		endpoint, needSite = epSceneInfo, true
		payload = map[string]any{"site_id": pp.SiteID}
	case "charge-energy":
		// Anker's energy_analysis is site-scoped; an empty device_sn returns the
		// site's EV-charger totals, a serial narrows it to one charger.
		endpoint, needSite = epEnergyAnalysis, true
		payload = map[string]any{
			"site_id": pp.SiteID, "device_sn": pp.SN, "device_type": "ev_charger",
			"type": energyRange(pp.Range), "start_time": pp.StartDate, "end_time": pp.EndDate,
		}
	case "vehicle":
		if pp.VehicleID == "" {
			return nil, fmt.Errorf("anker-solix: action %q requires a vehicleId", action)
		}
		endpoint = epVehicleDetail
		payload = map[string]any{"vehicle_id": pp.VehicleID}
	default:
		return nil, fmt.Errorf("anker-solix: unknown action %q", action)
	}
	if needSN && pp.SN == "" {
		return nil, fmt.Errorf("anker-solix: action %q requires an sn (EV charger serial)", action)
	}
	if needSite && pp.SiteID == "" {
		return nil, fmt.Errorf("anker-solix: action %q requires a siteId", action)
	}

	body, err := p.apiRequest(ctx, endpoint, payload)
	if err != nil {
		return nil, err
	}
	return json.RawMessage(body), nil
}

// energyRange normalizes the energy_analysis period, defaulting to a week like
// the reference implementation's EV-charger poll.
func energyRange(r string) string {
	switch strings.ToLower(strings.TrimSpace(r)) {
	case "day", "week", "month", "year":
		return strings.ToLower(strings.TrimSpace(r))
	default:
		return "week"
	}
}

// Shutdown releases pooled connections.
func (p *Plugin) Shutdown(context.Context) error {
	p.mu.Lock()
	defer p.mu.Unlock()
	if p.client != nil {
		p.client.CloseIdleConnections()
	}
	return nil
}

// ---- derived EV-charger state ------------------------------------------------

// evChargerState is one charger's live state, normalized out of whichever cloud
// view reported it. Status and mode names match anker-solix-api so a consumer
// can read them against the reference implementation.
type evChargerState struct {
	SN     string `json:"sn"`
	Name   string `json:"name,omitempty"`
	SiteID string `json:"siteId,omitempty"`
	Source string `json:"source"` // scene | hes — which view the record came from

	Status     *int   `json:"status,omitempty"` // raw operating_state / evChargerStatus
	StatusDesc string `json:"statusDesc"`

	// Mode is the operational mode the charger is effectively in; ModeOptions are
	// the modes it can be switched to from there. Charging is the binary reading
	// of Mode — everything but stop_charge counts as on.
	Mode        string   `json:"mode,omitempty"`
	ModeOptions []string `json:"modeOptions"`
	Charging    *bool    `json:"charging,omitempty"`

	Power          string `json:"power,omitempty"` // charge power as reported, unit per upstream
	OcppStatus     *int   `json:"ocppStatus,omitempty"`
	OcppStatusDesc string `json:"ocppStatusDesc,omitempty"`
}

// chargerState fetches a site's EV chargers from both cloud views and returns
// their normalized state. The two views cover different system families — the
// power_service scene for site systems, the HES service for HES systems — so a
// site answering only one of them is normal; the call fails only when neither
// view is reachable. An sn, when given, filters to that charger.
func (p *Plugin) chargerState(ctx context.Context, siteID, sn string) (json.RawMessage, error) {
	var (
		out      []evChargerState
		sceneErr error
		hesErr   error
	)

	if body, err := p.apiRequest(ctx, epSceneInfo, map[string]any{"site_id": siteID}); err != nil {
		sceneErr = err
	} else {
		out = append(out, parseScenePiles(body, siteID)...)
	}
	if body, err := p.apiRequest(ctx, epSystemRunInfo, map[string]any{"siteId": siteID}); err != nil {
		hesErr = err
	} else {
		out = append(out, parseHesChargers(body, siteID)...)
	}
	if sceneErr != nil && hesErr != nil {
		return nil, fmt.Errorf("anker-solix: charger-state: no EV-charger view for site %s: %v; %v",
			siteID, sceneErr, hesErr)
	}

	// A charger reported by both views is one charger. The scene record wins: it
	// is the richer of the two, carrying charge power and OCPP status.
	seen := make(map[string]bool, len(out))
	kept := out[:0]
	for _, c := range out {
		if seen[c.SN] || (sn != "" && c.SN != sn) {
			continue
		}
		seen[c.SN] = true
		kept = append(kept, c)
	}
	out = kept
	if out == nil {
		out = []evChargerState{}
	}
	return json.Marshal(map[string]any{"siteId": siteID, "chargers": out})
}

// parseScenePiles reads the EV chargers out of a get_scen_info response. The
// scene calls the state operating_state and the charge power just power; the
// reference implementation renames both on ingest, and so do we.
func parseScenePiles(body []byte, siteID string) []evChargerState {
	var env struct {
		Data struct {
			ChargingPileInfo struct {
				ChargingPileList []struct {
					DeviceSN       string      `json:"device_sn"`
					DeviceName     string      `json:"device_name"`
					OperatingState *int        `json:"operating_state"`
					Power          json.Number `json:"power"`
					OcppConnect    *int        `json:"ocpp_connect_status"`
				} `json:"charging_pile_list"`
			} `json:"charging_pile_info"`
		} `json:"data"`
	}
	if err := json.Unmarshal(body, &env); err != nil {
		return nil
	}
	list := env.Data.ChargingPileInfo.ChargingPileList
	out := make([]evChargerState, 0, len(list))
	for _, cp := range list {
		if cp.DeviceSN == "" {
			continue
		}
		out = append(out, newChargerState(cp.DeviceSN, cp.DeviceName, siteID, "scene",
			cp.OperatingState, cp.OcppConnect, cp.Power.String()))
	}
	return out
}

// parseHesChargers reads the EV chargers out of a get_system_running_info
// response, where they arrive as evChargerInfos under their own field names.
func parseHesChargers(body []byte, siteID string) []evChargerState {
	var env struct {
		Data struct {
			EvChargerInfos []struct {
				SN     string `json:"evChargerSn"`
				Name   string `json:"evChargerName"`
				Status *int   `json:"evChargerStatus"`
			} `json:"evChargerInfos"`
		} `json:"data"`
	}
	if err := json.Unmarshal(body, &env); err != nil {
		return nil
	}
	out := make([]evChargerState, 0, len(env.Data.EvChargerInfos))
	for _, ev := range env.Data.EvChargerInfos {
		if ev.SN == "" {
			continue
		}
		out = append(out, newChargerState(ev.SN, ev.Name, siteID, "hes", ev.Status, nil, ""))
	}
	return out
}

// newChargerState decorates a raw status code with its name, mode and options.
func newChargerState(sn, name, siteID, source string, status, ocpp *int, power string) evChargerState {
	c := evChargerState{
		SN: sn, Name: name, SiteID: siteID, Source: source,
		Status: status, StatusDesc: stateUnknown, Power: power,
		ModeOptions: []string{},
	}
	if status != nil {
		c.StatusDesc = statusName(*status)
		// The cloud views carry no boost flag and no countdowns — those reach the
		// reference implementation over MQTT only — so the mode derives from the
		// status alone and a charger never reads as boosting or waiting here.
		c.Mode = chargerMode(c.StatusDesc, false, 0, 0)
		c.ModeOptions = chargerModeOptions(c.Mode, c.StatusDesc)
		on := c.Mode != modeStopCharge
		c.Charging = &on
	}
	if ocpp != nil {
		c.OcppStatus = ocpp
		desc, ok := ocppConnStatus[*ocpp]
		if !ok {
			desc = stateUnknown
		}
		c.OcppStatusDesc = desc
	}
	return c
}

// statusName maps an operating-state code to its name.
func statusName(code int) string {
	if name, ok := evChargerStatus[code]; ok {
		return name
	}
	return stateUnknown
}

// chargerMode derives the operational mode from the charger's status, mirroring
// anker-solix-api's ev_charger_mode_state. boost and the two countdowns are MQTT
// signals; pass their zero values when only cloud data is available.
func chargerMode(statusDesc string, boost bool, plugCountdown, startCountdown int) string {
	if boost {
		return modeBoostCharge
	}
	switch statusDesc {
	case statePreparing:
		if plugCountdown > 0 {
			return modeWaitPlug
		}
		if startCountdown > 0 {
			return modeWaitStart
		}
		return modeStartCharge
	case stateCharging, stateChargerPaused, stateVehiclePaused:
		return modeStartCharge
	default:
		return modeStopCharge
	}
}

// chargerModeOptions lists the modes reachable from the current one, mirroring
// ev_charger_mode_options. The result is sorted so the output is stable.
func chargerModeOptions(mode, statusDesc string) []string {
	if mode == "" {
		return []string{}
	}
	set := map[string]bool{mode: true}
	switch mode {
	case modeWaitPlug, modeWaitStart, modeStartCharge:
		set[modeStopCharge] = true
		// A start delay can only be skipped while it is running; boost only applies
		// once charging has been commanded.
		if mode == modeWaitStart {
			set[modeSkipDelay] = true
		} else if mode == modeStartCharge {
			set[modeBoostCharge] = true
		}
	case modeBoostCharge:
		set[modeStopCharge] = true
	default:
		// Only a charger sitting in standby can be told to start.
		if statusDesc == stateStandby {
			set[modeStartCharge] = true
		}
	}
	opts := make([]string, 0, len(set))
	for m := range set {
		opts = append(opts, m)
	}
	sort.Strings(opts)
	return opts
}

// ---- token management --------------------------------------------------------

// Login backoff. A refused sign-in is cached and replayed to every caller until
// its window passes, so credentials Anker rejects are offered once, not once per
// request.
const (
	loginRetryBase = 1 * time.Minute
	loginRetryMax  = 15 * time.Minute

	// codeSignInLocked is what Anker answers once it has already disabled the
	// account for repeated failures; it states a ten-minute penalty, so sit the
	// penalty out rather than spending attempts against a door that is shut.
	codeSignInLocked = 10019
	loginLockoutWait = 10 * time.Minute
)

// loginRejected is the login endpoint answering with a non-zero API code. The
// code is kept so an already-locked account can be told from an ordinary
// refusal.
type loginRejected struct {
	code int
	msg  string
}

func (e *loginRejected) Error() string {
	return fmt.Sprintf("anker-solix: login rejected (code %d): %s", e.code, e.msg)
}

// loginFailure wraps whatever made a login attempt fail, together with the time
// before which no further attempt is made.
type loginFailure struct {
	err     error
	retryAt time.Time
}

func (e *loginFailure) Error() string {
	wait := time.Until(e.retryAt).Round(time.Second)
	if wait < 0 {
		wait = 0
	}
	return fmt.Sprintf("%s (not retrying for %s)", e.err, wait)
}

func (e *loginFailure) Unwrap() error { return e.err }

// isLoginFailure reports whether err came from the login exchange rather than
// from the endpoint the caller was asking for — the difference between "this
// account cannot sign in" and "this one view said no".
func isLoginFailure(err error) bool {
	var lf *loginFailure
	return errors.As(err, &lf)
}

// ensureToken guarantees a non-expired auth token, logging in as needed.
// Serialized by p.mu so concurrent requests trigger at most one login.
func (p *Plugin) ensureToken(ctx context.Context) (tokenInfo, error) {
	s := p.sess
	if s == nil {
		return tokenInfo{}, errors.New("anker-solix: plugin not initialised")
	}
	s.mu.Lock()
	defer s.mu.Unlock()

	if s.tok != nil && time.Now().Before(s.tok.expiration) {
		return *s.tok, nil
	}
	if err := p.attemptLogin(ctx); err != nil {
		return tokenInfo{}, err
	}
	return *s.tok, nil
}

// attemptLogin logs in at most once per backoff window, handing every caller in
// between the failure that opened it. Caller holds p.sess.mu.
func (p *Plugin) attemptLogin(ctx context.Context) error {
	if p.email == "" || p.password == "" {
		// Nothing was sent to Anker, so there is nothing to back off from.
		return errors.New("anker-solix: email and password are required")
	}
	s := p.sess
	if s.loginErr != nil && time.Now().Before(s.loginRetryAt) {
		return s.loginErr
	}
	s.noteLogin(p.login(ctx))
	return s.loginErr
}

// login performs the ECDH + AES password exchange against passport/login and
// stores the returned token. Caller holds p.mu.
func (p *Plugin) login(ctx context.Context) error {
	// Fresh ephemeral P-256 key pair and shared secret against Anker's server key.
	curve := ecdh.P256()
	priv, err := curve.GenerateKey(rand.Reader)
	if err != nil {
		return fmt.Errorf("anker-solix: generate key: %w", err)
	}
	serverBytes, err := hex.DecodeString(serverPublicKeyHex)
	if err != nil {
		return fmt.Errorf("anker-solix: server key: %w", err)
	}
	serverPub, err := curve.NewPublicKey(serverBytes)
	if err != nil {
		return fmt.Errorf("anker-solix: server key: %w", err)
	}
	shared, err := priv.ECDH(serverPub)
	if err != nil {
		return fmt.Errorf("anker-solix: derive shared key: %w", err)
	}
	encPassword, err := encryptPassword(p.password, shared)
	if err != nil {
		return fmt.Errorf("anker-solix: %w", err)
	}

	gmt, offsetMs := timezone()
	reqBody := map[string]any{
		"ab":                 p.countryId,
		"client_secret_info": map[string]any{"public_key": hex.EncodeToString(priv.PublicKey().Bytes())},
		"enc":                0,
		"email":              p.email,
		"password":           encPassword,
		"time_zone":          offsetMs,
		"transaction":        fmt.Sprintf("%d", time.Now().UnixMilli()),
	}

	body, status, err := p.doRequest(ctx, epLogin, reqBody, "", "", gmt)
	if err != nil {
		return err
	}
	if status != http.StatusOK {
		return fmt.Errorf("anker-solix: login failed (HTTP %d): %s", status, shorten(string(body)))
	}
	return p.storeToken(body)
}

// storeToken parses the login envelope and updates the session's token. Caller
// holds p.sess.mu.
func (p *Plugin) storeToken(body []byte) error {
	var env struct {
		Code int    `json:"code"`
		Msg  string `json:"msg"`
		Data struct {
			AuthToken    string `json:"auth_token"`
			UserID       string `json:"user_id"`
			NickName     string `json:"nick_name"`
			TokenExpires int64  `json:"token_expires_at"`
		} `json:"data"`
	}
	if err := json.Unmarshal(body, &env); err != nil {
		return fmt.Errorf("anker-solix: decode login response: %w", err)
	}
	if env.Code != 0 {
		return &loginRejected{code: env.Code, msg: shorten(env.Msg)}
	}
	if env.Data.AuthToken == "" || env.Data.UserID == "" {
		return errors.New("anker-solix: login response missing auth_token or user_id")
	}

	// token_expires_at is a unix timestamp (seconds); Anker tokens live ~7 days.
	// Fall back to a conservative 6-day lifetime if the field is absent.
	exp := time.Now().Add(6 * 24 * time.Hour)
	if env.Data.TokenExpires > 0 {
		exp = time.Unix(env.Data.TokenExpires, 0)
	}
	exp = exp.Add(-tokenExpiryMargin)

	p.sess.tok = &tokenInfo{
		authToken:  env.Data.AuthToken,
		gtoken:     md5hex(env.Data.UserID),
		nickname:   env.Data.NickName,
		expiration: exp,
	}
	return nil
}

// ---- data requests -----------------------------------------------------------

// apiRequest performs an authenticated POST, re-authenticating once if the token
// is rejected. It returns the raw response body; a non-zero API code or non-2xx
// status is returned as an error.
func (p *Plugin) apiRequest(ctx context.Context, endpoint string, payload map[string]any) ([]byte, error) {
	tok, err := p.ensureToken(ctx)
	if err != nil {
		return nil, err
	}

	gmt, _ := timezone()
	body, status, err := p.doRequest(ctx, endpoint, payload, tok.authToken, tok.gtoken, gmt)
	if err != nil {
		return nil, err
	}

	// A rejected token surfaces as 401/403 or an auth error code; log in afresh
	// and retry once.
	if status == http.StatusUnauthorized || status == http.StatusForbidden || isAuthCode(body) {
		p.sess.mu.Lock()
		p.sess.tok = nil
		lerr := p.attemptLogin(ctx)
		var newTok tokenInfo
		if lerr == nil {
			newTok = *p.sess.tok
		}
		p.sess.mu.Unlock()
		if lerr != nil {
			return nil, lerr
		}
		body, status, err = p.doRequest(ctx, endpoint, payload, newTok.authToken, newTok.gtoken, gmt)
		if err != nil {
			return nil, err
		}
	}

	if status != http.StatusOK {
		return nil, fmt.Errorf("anker-solix: request %s failed (HTTP %d): %s", endpoint, status, shorten(string(body)))
	}
	if code, msg, ok := apiError(body); ok {
		return nil, fmt.Errorf("anker-solix: request %s failed (code %d): %s", endpoint, code, shorten(msg))
	}
	return body, nil
}

// doRequest issues a single POST to an endpoint with the common Anker headers.
// When authToken is empty the auth headers are omitted (login request).
func (p *Plugin) doRequest(ctx context.Context, endpoint string, payload map[string]any, authToken, gtoken, gmt string) ([]byte, int, error) {
	buf, err := json.Marshal(payload)
	if err != nil {
		return nil, 0, fmt.Errorf("anker-solix: encode request: %w", err)
	}
	url := p.apiBase + "/" + endpoint
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(buf))
	if err != nil {
		return nil, 0, err
	}
	req.Header.Set("content-type", "application/json")
	req.Header.Set("model-type", "DESKTOP")
	req.Header.Set("app-name", "anker_power")
	req.Header.Set("os-type", "android")
	req.Header.Set("country", p.countryId)
	req.Header.Set("timezone", gmt)
	if authToken != "" {
		req.Header.Set("x-auth-token", authToken)
		req.Header.Set("gtoken", gtoken)
	}

	resp, err := p.client.Do(req)
	if err != nil {
		return nil, 0, fmt.Errorf("anker-solix: request %s: %w", endpoint, err)
	}
	defer drain(resp)
	respBody, _ := io.ReadAll(io.LimitReader(resp.Body, 8<<20))
	return respBody, resp.StatusCode, nil
}

// ---- crypto & small helpers --------------------------------------------------

// encryptPassword AES-256-CBC encrypts the password under the ECDH shared secret
// (key = secret, IV = secret[:16], PKCS#7 padding) and base64-encodes it.
func encryptPassword(password string, shared []byte) (string, error) {
	if len(shared) < 32 {
		return "", fmt.Errorf("shared key too short: %d bytes", len(shared))
	}
	block, err := aes.NewCipher(shared)
	if err != nil {
		return "", fmt.Errorf("aes cipher: %w", err)
	}
	plain := pkcs7Pad([]byte(password), block.BlockSize())
	out := make([]byte, len(plain))
	cipher.NewCBCEncrypter(block, shared[:block.BlockSize()]).CryptBlocks(out, plain)
	return base64.StdEncoding.EncodeToString(out), nil
}

// pkcs7Pad appends PKCS#7 padding to a multiple of blockSize.
func pkcs7Pad(data []byte, blockSize int) []byte {
	pad := blockSize - len(data)%blockSize
	return append(data, bytes.Repeat([]byte{byte(pad)}, pad)...)
}

// md5hex returns the lowercase hex MD5 of s (Anker's gtoken derivation).
func md5hex(s string) string {
	sum := md5.Sum([]byte(s))
	return hex.EncodeToString(sum[:])
}

// timezone returns Anker's GMT offset string (e.g. "GMT+01:00") and the offset
// in milliseconds, both derived from the host's local zone.
func timezone() (string, int) {
	_, offsetSec := time.Now().Zone()
	sign := "+"
	abs := offsetSec
	if abs < 0 {
		sign, abs = "-", -abs
	}
	gmt := fmt.Sprintf("GMT%s%02d:%02d", sign, abs/3600, (abs%3600)/60)
	return gmt, offsetSec * 1000
}

// apiError reports a non-zero API code (and its message) from a response body.
func apiError(body []byte) (int, string, bool) {
	var env struct {
		Code int    `json:"code"`
		Msg  string `json:"msg"`
	}
	if err := json.Unmarshal(body, &env); err != nil {
		return 0, "", false
	}
	if env.Code != 0 {
		return env.Code, env.Msg, true
	}
	return 0, "", false
}

// isAuthCode reports whether a response body carries an authentication-failure
// API code (token invalid/expired), warranting a re-login.
func isAuthCode(body []byte) bool {
	code, _, ok := apiError(body)
	if !ok {
		return false
	}
	// Anker returns 401xx-family codes for token problems; treat the common
	// invalid/expired-token codes as auth failures.
	switch code {
	case 401, 40100, 40101, 40102, 40103:
		return true
	}
	return false
}

// countChargers best-effort extracts the bound EV-charger count from a
// get_user_bind_and_not_in_station_evchargers response.
func countChargers(body []byte) (int, bool) {
	var env struct {
		Data struct {
			EvChargers            []json.RawMessage `json:"evChargers"`
			UserBindEvChargersCnt *int              `json:"userBindEvChargersCount"`
		} `json:"data"`
	}
	if err := json.Unmarshal(body, &env); err != nil {
		return 0, false
	}
	if env.Data.UserBindEvChargersCnt != nil {
		return *env.Data.UserBindEvChargersCnt, true
	}
	if env.Data.EvChargers != nil {
		return len(env.Data.EvChargers), true
	}
	return 0, false
}

// drain closes a response body after discarding any remainder so the connection
// can be reused.
func drain(resp *http.Response) {
	if resp != nil && resp.Body != nil {
		_, _ = io.Copy(io.Discard, io.LimitReader(resp.Body, 1<<20))
		_ = resp.Body.Close()
	}
}

// shorten trims long/multiline upstream messages for health details and errors.
func shorten(s string) string {
	s = strings.TrimSpace(strings.ReplaceAll(s, "\n", " "))
	if len(s) > 200 {
		return s[:200] + "…"
	}
	return s
}