package extsvc

import (
	"context"
	"fmt"
	"math/rand"
	"net/http"
	"strings"
	"sync"
	"time"
)

// baseCall extracts the operator's base callsign from a possibly-affixed call:
// for slashed forms (F4BPO/P, FW/F4BPO, 9A/F4BPO/P) it returns the longest
// token, which is the real call; otherwise the call itself. Upper-cased.
func baseCall(s string) string {
	s = strings.ToUpper(strings.TrimSpace(s))
	if !strings.Contains(s, "/") {
		return s
	}
	best := ""
	for _, part := range strings.Split(s, "/") {
		if len(part) > len(best) {
			best = part
		}
	}
	return best
}

// sameBaseCall reports whether two callsigns belong to the same operator,
// ignoring portable prefixes/suffixes (F4BPO/P == F4BPO, FW/F4BPO == F4BPO).
func sameBaseCall(a, b string) bool {
	return baseCall(a) == baseCall(b)
}

// SameBaseCall is the exported form of sameBaseCall, so the host app can apply
// the same "same operator?" rule when filtering an on-close upload batch by the
// active logbook's callsign.
func SameBaseCall(a, b string) bool { return sameBaseCall(a, b) }

// Deps are the host-app callbacks the Manager needs. Keeping them as
// function fields decouples extsvc from the qso/adif/settings packages and
// keeps the upload-scheduling logic testable.
type Deps struct {
	Client *http.Client

	// BuildADIF returns the ADIF record for a QSO id, with STATION_CALLSIGN
	// overridden by forceCall when non-empty. ok=false means "skip silently"
	// (row gone, missing required fields, …).
	BuildADIF func(id int64, forceCall string) (record string, ok bool)

	// MarkUploaded stamps the per-service upload status on the QSO row and
	// notifies the UI. Called once, on success.
	MarkUploaded func(svc Service, id int64, logID string)

	// NotifyError surfaces a failed upload (logging + optional UI event).
	NotifyError func(svc Service, id int64, err error)

	// ShouldUpload reports whether a QSO is eligible for upload to this
	// service, based on its sent status: QRZ/Club Log upload anything not
	// yet "Y"; LoTW uploads only QSOs whose lotw_sent matches the configured
	// Upload flag ("N" or "R"), à la Log4OM. Returning false skips the QSO.
	ShouldUpload func(svc Service, id int64) bool

	// StationCallOf returns the QSO's STATION_CALLSIGN. Used to guard against
	// uploading a QSO into a logbook for a different callsign (the force-call
	// option would otherwise silently relabel it). "" → no station call known.
	StationCallOf func(id int64) string

	// CloseUploadIDs returns the QSO ids to upload for a service when the app
	// closes — scanning the WHOLE logbook, not just this session: LoTW returns
	// rows whose lotw_sent matches the configured status set; QRZ/Club Log
	// return anything not yet "Y". This is what makes an imported ADIF (old
	// QSOs still marked unsent) upload on close. nil → nothing to do.
	CloseUploadIDs func(svc Service) []int64

	// Logf is an optional diagnostic logger.
	Logf func(format string, args ...any)
}

// Manager owns the external-service config snapshot and schedules uploads
// when a QSO is logged. Immediate uploads run in their own goroutine;
// delayed uploads use a timer with a random 1–2 minute fuse.
type Manager struct {
	deps Deps

	mu  sync.Mutex
	cfg ExternalServices
	rnd *rand.Rand

	// uploadCh serialises immediate auto-uploads through a single worker. Firing a
	// goroutine per QSO meant a pileup / ADIF-import burst hit a service with dozens
	// of concurrent requests at once — Club Log's nginx answers that with 403, the
	// upload is counted as failed and the QSO stays at "R" despite the others going
	// through. One-at-a-time with a small gap keeps every upload under the limit.
	uploadCh chan uploadJob
}

// uploadJob is one queued auto-upload.
type uploadJob struct {
	svc     Service
	id      int64
	cfg     ServiceConfig
	attempt int // 0 on first try; incremented on each retry
}

// uploadGap spaces serialized uploads so a burst never trips a service's per-IP
// rate limiter. maxUploadAttempts bounds retries of a transient failure.
const (
	uploadGap         = 250 * time.Millisecond
	maxUploadAttempts = 4
)

func NewManager(deps Deps) *Manager {
	if deps.Client == nil {
		deps.Client = &http.Client{Timeout: 20 * time.Second}
	}
	m := &Manager{
		deps: deps,
		// Seeded from the clock; the delay only needs to be unpredictable
		// enough to spread bursts, not cryptographically random.
		rnd:      rand.New(rand.NewSource(time.Now().UnixNano())),
		uploadCh: make(chan uploadJob, 4096),
	}
	go m.uploadWorker()
	return m
}

// uploadWorker drains the queue one upload at a time, spacing them so a burst of
// freshly-logged QSOs can't hammer (and get 403'd by) a service. A transient
// failure is re-queued with an exponential back-off, so a QSO that hit a
// momentary rate-limit still ends up marked instead of stuck at "R".
func (m *Manager) uploadWorker() {
	for job := range m.uploadCh {
		ok, retryable := m.upload(job.svc, job.id, job.cfg)
		if !ok && retryable && job.attempt+1 < maxUploadAttempts {
			next := job
			next.attempt++
			backoff := time.Duration(1<<uint(job.attempt)) * time.Second // 1s, 2s, 4s…
			m.logf("extsvc: %s upload of QSO %d will retry (attempt %d) in %s", job.svc, job.id, next.attempt+1, backoff)
			time.AfterFunc(backoff, func() { m.enqueueJob(next) })
		}
		time.Sleep(uploadGap)
	}
}

// enqueueUpload queues a first-attempt upload without blocking the logging path.
func (m *Manager) enqueueUpload(svc Service, id int64, cfg ServiceConfig) {
	m.enqueueJob(uploadJob{svc: svc, id: id, cfg: cfg})
}

// enqueueJob queues a job (possibly a retry). If the queue is somehow full (an
// enormous burst), it falls back to a goroutine rather than dropping the upload —
// a dropped upload would leave the QSO stuck at "R".
func (m *Manager) enqueueJob(job uploadJob) {
	select {
	case m.uploadCh <- job:
	default:
		go m.upload(job.svc, job.id, job.cfg)
	}
}

func (m *Manager) logf(format string, args ...any) {
	if m.deps.Logf != nil {
		m.deps.Logf(format, args...)
	}
}

// SetConfig replaces the active config snapshot (called after the user
// saves the External Services settings).
func (m *Manager) SetConfig(cfg ExternalServices) {
	m.mu.Lock()
	defer m.mu.Unlock()
	cfg.QRZ = cfg.QRZ.normalised()
	cfg.Clublog = cfg.Clublog.normalised()
	cfg.LoTW = cfg.LoTW.normalised()
	cfg.HRDLog = cfg.HRDLog.normalised()
	cfg.EQSL = cfg.EQSL.normalised()
	m.cfg = cfg
}

// Config returns the current snapshot.
func (m *Manager) Config() ExternalServices {
	m.mu.Lock()
	defer m.mu.Unlock()
	return m.cfg
}

// delaySeconds returns a random 60–120s fuse for delayed uploads.
func (m *Manager) delaySeconds() time.Duration {
	m.mu.Lock()
	d := 60 + m.rnd.Intn(61) // [60, 120]
	m.mu.Unlock()
	return time.Duration(d) * time.Second
}

// OnQSOLogged is called after a QSO is inserted (manual entry or UDP
// auto-log). It fans out to every enabled, auto-upload service in the
// configured timing mode. Returns immediately.
func (m *Manager) OnQSOLogged(id int64) {
	cfg := m.Config()

	// QRZ.com
	if qrz := cfg.QRZ; qrz.AutoUpload && qrz.APIKey != "" {
		m.route(ServiceQRZ, id, qrz)
	}
	// Club Log — email + password + callsign are enough (no API key).
	if cl := cfg.Clublog; cl.AutoUpload && cl.Email != "" && cl.Password != "" {
		m.route(ServiceClublog, id, cl)
	}
	// LoTW — needs TQSL + a station location.
	if lt := cfg.LoTW; lt.AutoUpload && lt.TQSLPath != "" && lt.StationLocation != "" {
		m.route(ServiceLoTW, id, lt)
	}
	// HRDLog — needs the station callsign + the account upload code.
	if h := cfg.HRDLog; h.AutoUpload && h.Callsign != "" && h.Code != "" {
		m.route(ServiceHRDLog, id, h)
	}
	// eQSL — needs the account username (callsign) + password.
	if e := cfg.EQSL; e.AutoUpload && e.Username != "" && e.Password != "" {
		m.route(ServiceEQSL, id, e)
	}
}

// route sends a logged QSO down the configured timing path: queue it for the
// app-close batch, or schedule an immediate / delayed upload.
func (m *Manager) route(svc Service, id int64, cfg ServiceConfig) {
	if cfg.UploadMode == ModeOnClose {
		// Nothing to queue: on-close upload sweeps the whole logbook from the
		// database at shutdown (see FlushOnClose), so this QSO is picked up by
		// its sent-status then — no in-memory tracking needed.
		return
	}
	m.scheduleUpload(svc, id, cfg)
}

// scheduleUpload either queues the upload now (immediate) or arms a timer that
// queues it later (delayed). Both go through the serialised worker so uploads are
// never fired concurrently in a burst.
func (m *Manager) scheduleUpload(svc Service, id int64, cfg ServiceConfig) {
	if cfg.UploadMode == ModeDelayed {
		d := m.delaySeconds()
		m.logf("extsvc: %s upload of QSO %d scheduled in %s", svc, id, d)
		time.AfterFunc(d, func() { m.enqueueUpload(svc, id, cfg) })
		return
	}
	m.enqueueUpload(svc, id, cfg)
}

// onCloseServices returns the services configured for on-close auto-upload,
// with the minimum credentials to actually run.
func (m *Manager) onCloseServices() []Service {
	cfg := m.Config()
	var out []Service
	if q := cfg.QRZ; q.AutoUpload && q.UploadMode == ModeOnClose && q.APIKey != "" {
		out = append(out, ServiceQRZ)
	}
	if c := cfg.Clublog; c.AutoUpload && c.UploadMode == ModeOnClose && c.Email != "" && c.Password != "" {
		out = append(out, ServiceClublog)
	}
	if l := cfg.LoTW; l.AutoUpload && l.UploadMode == ModeOnClose && l.TQSLPath != "" && l.StationLocation != "" {
		out = append(out, ServiceLoTW)
	}
	if h := cfg.HRDLog; h.AutoUpload && h.UploadMode == ModeOnClose && h.Callsign != "" && h.Code != "" {
		out = append(out, ServiceHRDLog)
	}
	if e := cfg.EQSL; e.AutoUpload && e.UploadMode == ModeOnClose && e.Username != "" && e.Password != "" {
		out = append(out, ServiceEQSL)
	}
	return out
}

// CloseUploadCount returns how many QSOs across the whole logbook would be
// uploaded at app close (sum over every on-close service). The shutdown
// sequence uses it to decide whether to show the upload step and its label.
func (m *Manager) CloseUploadCount() int {
	if m.deps.CloseUploadIDs == nil {
		return 0
	}
	n := 0
	for _, svc := range m.onCloseServices() {
		n += len(m.deps.CloseUploadIDs(svc))
	}
	return n
}

// FlushOnClose uploads every QSO due for an on-close push, scanning the whole
// logbook (not just this session). Called from the shutdown sequence. QRZ/Club
// Log go one-by-one (fast HTTP); LoTW is signed and uploaded as a single TQSL
// batch. Returns the number of QSOs uploaded successfully.
func (m *Manager) FlushOnClose() int {
	if m.deps.CloseUploadIDs == nil {
		return 0
	}
	cfg := m.Config()
	uploaded := 0
	for _, svc := range m.onCloseServices() {
		ids := m.deps.CloseUploadIDs(svc)
		if len(ids) == 0 {
			continue
		}
		switch svc {
		case ServiceLoTW:
			uploaded += m.flushLoTWBatch(ids, cfg.LoTW)
		case ServiceQRZ:
			for _, id := range ids {
				if ok, _ := m.upload(svc, id, cfg.QRZ); ok {
					uploaded++
				}
			}
		case ServiceClublog:
			for _, id := range ids {
				if ok, _ := m.upload(svc, id, cfg.Clublog); ok {
					uploaded++
				}
			}
		case ServiceHRDLog:
			for _, id := range ids {
				if ok, _ := m.upload(svc, id, cfg.HRDLog); ok {
					uploaded++
				}
			}
		case ServiceEQSL:
			for _, id := range ids {
				if ok, _ := m.upload(svc, id, cfg.EQSL); ok {
					uploaded++
				}
			}
		}
	}
	return uploaded
}

// flushLoTWBatch signs+uploads all queued LoTW QSOs in one TQSL run, then
// stamps each as uploaded on success.
func (m *Manager) flushLoTWBatch(ids []int64, cfg ServiceConfig) int {
	var records []string
	var kept []int64
	for _, id := range ids {
		// Skip QSOs not eligible (sent status doesn't match Upload flag).
		if m.deps.ShouldUpload != nil && !m.deps.ShouldUpload(ServiceLoTW, id) {
			continue
		}
		// Override STATION_CALLSIGN so /P etc. signs against the base cert.
		if rec, ok := m.deps.BuildADIF(id, cfg.ForceStationCallsign); ok {
			records = append(records, rec)
			kept = append(kept, id)
		}
	}
	if len(records) == 0 {
		return 0
	}
	res, err := UploadLoTW(context.Background(), cfg, "", strings.Join(records, "\n"))
	if err != nil || !res.OK {
		if err == nil {
			err = errFromResult(res)
		}
		m.logf("extsvc: lotw batch upload (%d QSOs) failed: %v", len(kept), err)
		if m.deps.NotifyError != nil {
			m.deps.NotifyError(ServiceLoTW, 0, err)
		}
		return 0
	}
	m.logf("extsvc: lotw batch upload OK (%d QSOs)", len(kept))
	if m.deps.MarkUploaded != nil {
		for _, id := range kept {
			m.deps.MarkUploaded(ServiceLoTW, id, res.LogID)
		}
	}
	return len(kept)
}

// upload performs the actual push and returns true on success. It builds a
// fresh, lifecycle-independent context so a delayed upload still completes
// even if it fires close to shutdown.
// upload performs one upload. It returns ok=true when the QSO was uploaded (and
// marked), and retryable=true when it failed in a way worth retrying later (an
// HTTP/service error such as a rate-limit 403) as opposed to a permanent skip
// (not eligible, wrong station callsign, no record).
func (m *Manager) upload(svc Service, id int64, cfg ServiceConfig) (ok bool, retryable bool) {
	// Skip QSOs that aren't eligible (already sent, or sent status doesn't
	// match the configured Upload flag).
	if m.deps.ShouldUpload != nil && !m.deps.ShouldUpload(svc, id) {
		m.logf("extsvc: %s upload of QSO %d skipped (not eligible)", svc, id)
		return false, false
	}

	// Station-callsign guard. Each logbook belongs to one callsign:
	//   QRZ/LoTW → the ForceStationCallsign (the call this logbook signs as)
	//   Club Log → the logbook Callsign param
	// If the QSO's own STATION_CALLSIGN is a DIFFERENT operator, uploading
	// would push it into the wrong logbook (and the force-call option would
	// silently relabel it). Block it with a clear error. Portable variants of
	// the SAME call (F4BPO/P, FW/F4BPO…) are allowed.
	owner := ""
	switch svc {
	case ServiceQRZ, ServiceLoTW:
		owner = cfg.ForceStationCallsign
	case ServiceClublog, ServiceHRDLog:
		owner = cfg.Callsign
	case ServiceEQSL:
		owner = cfg.Username
	}
	if owner != "" && m.deps.StationCallOf != nil {
		qcall := m.deps.StationCallOf(id)
		if qcall != "" && !sameBaseCall(qcall, owner) {
			err := fmt.Errorf("station callsign %s does not match %s logbook %s — not uploaded",
				strings.ToUpper(qcall), svc, strings.ToUpper(owner))
			m.logf("extsvc: %s upload of QSO %d BLOCKED: %v", svc, id, err)
			if m.deps.NotifyError != nil {
				m.deps.NotifyError(svc, id, err)
			}
			return false, false
		}
	}

	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
	defer cancel()

	var res UploadResult
	var err error
	switch svc {
	case ServiceQRZ:
		// QRZ rewrites STATION_CALLSIGN to the registered call.
		record, ok := m.deps.BuildADIF(id, cfg.ForceStationCallsign)
		if !ok {
			m.logf("extsvc: %s upload of QSO %d skipped (no record)", svc, id)
			return false, false
		}
		res, err = UploadQRZ(ctx, m.deps.Client, cfg.APIKey, record)
	case ServiceClublog:
		// Club Log takes the logbook callsign as a separate param, so the
		// ADIF keeps the QSO's own station call (no override).
		record, ok := m.deps.BuildADIF(id, "")
		if !ok {
			m.logf("extsvc: %s upload of QSO %d skipped (no record)", svc, id)
			return false, false
		}
		res, err = UploadClublog(ctx, m.deps.Client, cfg, record)
	case ServiceLoTW:
		// LoTW signs via TQSL; an optional force-call overrides STATION_CALLSIGN
		// so the same cert can sign F4BPO, F4BPO/P, TM2Q… per profile.
		record, ok := m.deps.BuildADIF(id, cfg.ForceStationCallsign)
		if !ok {
			m.logf("extsvc: %s upload of QSO %d skipped (no record)", svc, id)
			return false, false
		}
		res, err = UploadLoTW(ctx, cfg, "", record)
	case ServiceHRDLog:
		// HRDLog takes the station callsign as a separate param, so the ADIF
		// keeps the QSO's own station call (no override), like Club Log.
		record, ok := m.deps.BuildADIF(id, "")
		if !ok {
			m.logf("extsvc: %s upload of QSO %d skipped (no record)", svc, id)
			return false, false
		}
		res, err = UploadHRDLog(ctx, m.deps.Client, cfg.Callsign, cfg.Code, record)
	case ServiceEQSL:
		// eQSL keeps the QSO's own station call; the account is identified by
		// the Username + Password, with an optional QTH nickname.
		record, ok := m.deps.BuildADIF(id, "")
		if !ok {
			m.logf("extsvc: %s upload of QSO %d skipped (no record)", svc, id)
			return false, false
		}
		res, err = UploadEQSL(ctx, m.deps.Client, cfg.Username, cfg.Password, cfg.QTHNickname, record)
	default:
		return false, false
	}

	if err != nil || !res.OK {
		if err == nil {
			err = errFromResult(res)
		}
		m.logf("extsvc: %s upload of QSO %d failed: %v", svc, id, err)
		if m.deps.NotifyError != nil {
			m.deps.NotifyError(svc, id, err)
		}
		return false, true // transient (rate-limit / network) → worth a retry
	}

	m.logf("extsvc: %s upload of QSO %d OK (logid=%q)", svc, id, res.LogID)
	if m.deps.MarkUploaded != nil {
		m.deps.MarkUploaded(svc, id, res.LogID)
	}
	return true, false
}