package service

import (
	"context"
	"fmt"
	"log/slog"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/Wei-Shaw/sub2api/internal/config"
	"github.com/Wei-Shaw/sub2api/internal/pkg/lspool"
)

const (
	defaultLSPoolBootstrapConcurrency = 4
)

type lsBootstrapAccountReader interface {
	ListByPlatform(ctx context.Context, platform string) ([]Account, error)
}

// LSPoolBootstrapService pre-creates LS workers for eligible Antigravity accounts on startup.
type LSPoolBootstrapService struct {
	accountReader lsBootstrapAccountReader
	backend       lspool.Backend
	cfg           *config.Config
	logger        *slog.Logger

	ctx    context.Context
	cancel context.CancelFunc

	once sync.Once
	wg   sync.WaitGroup
}

func NewLSPoolBootstrapService(accountReader lsBootstrapAccountReader, backend lspool.Backend, cfg *config.Config) *LSPoolBootstrapService {
	ctx, cancel := context.WithCancel(context.Background())
	return &LSPoolBootstrapService{
		accountReader: accountReader,
		backend:       backend,
		cfg:           cfg,
		logger:        slog.Default().With("component", "service.lspool_bootstrap"),
		ctx:           ctx,
		cancel:        cancel,
	}
}

// ProvideLSPoolBootstrapService creates and starts the LS pool bootstrap worker.
func ProvideLSPoolBootstrapService(accountRepo AccountRepository, cfg *config.Config) *LSPoolBootstrapService {
	svc := NewLSPoolBootstrapService(accountRepo, lspool.GlobalPool(cfg), cfg)
	svc.Start()
	return svc
}

func (s *LSPoolBootstrapService) Start() {
	if s == nil {
		return
	}
	s.once.Do(func() {
		if s.backend == nil {
			if lspool.IsLSModeEnabled() {
				s.logger.Warn("startup bootstrap skipped: ls backend unavailable")
			}
			return
		}
		s.wg.Add(1)
		go func() {
			defer s.wg.Done()
			s.bootstrap(s.ctx)
		}()
	})
}

func (s *LSPoolBootstrapService) Stop() {
	if s == nil {
		return
	}
	s.cancel()
	s.wg.Wait()
}

func (s *LSPoolBootstrapService) bootstrap(ctx context.Context) {
	if s.backend == nil || s.accountReader == nil {
		return
	}

	accounts, err := s.accountReader.ListByPlatform(ctx, PlatformAntigravity)
	if err != nil {
		s.logger.Warn("load antigravity accounts for ls bootstrap failed", "error", err)
		return
	}

	now := time.Now()
	candidates := make([]Account, 0, len(accounts))
	for i := range accounts {
		if shouldBootstrapLSPoolAccount(&accounts[i], now) {
			candidates = append(candidates, accounts[i])
		}
	}

	if len(candidates) == 0 {
		s.logger.Info("startup bootstrap skipped: no eligible antigravity accounts")
		return
	}

	s.logger.Info("starting ls worker bootstrap",
		"accounts_total", len(accounts),
		"accounts_eligible", len(candidates),
		"concurrency", s.bootstrapConcurrency())

	var (
		mu      sync.Mutex
		started int
		failed  int
	)
	sem := make(chan struct{}, s.bootstrapConcurrency())
	var wg sync.WaitGroup

loop:
	for i := range candidates {
		account := candidates[i]
		select {
		case <-ctx.Done():
			break loop
		case sem <- struct{}{}:
		}

		wg.Add(1)
		go func(account Account) {
			defer wg.Done()
			defer func() { <-sem }()

			if err := s.bootstrapAccount(&account); err != nil {
				mu.Lock()
				failed++
				mu.Unlock()
				s.logger.Warn("bootstrap ls worker failed", "account_id", account.ID, "error", err)
				return
			}

			mu.Lock()
			started++
			mu.Unlock()
			s.logger.Info("bootstrap ls worker ready", "account_id", account.ID)
		}(account)
	}

	wg.Wait()
	s.logger.Info("ls worker bootstrap completed",
		"accounts_total", len(accounts),
		"accounts_eligible", len(candidates),
		"workers_ready", started,
		"workers_failed", failed,
		"canceled", ctx.Err() != nil)
}

func (s *LSPoolBootstrapService) bootstrapAccount(account *Account) error {
	if s.backend == nil {
		return fmt.Errorf("ls backend unavailable")
	}
	if account == nil {
		return fmt.Errorf("account is nil")
	}

	accountKey := strconv.FormatInt(account.ID, 10)
	accessToken := strings.TrimSpace(account.GetCredential("access_token"))
	if accessToken == "" {
		return fmt.Errorf("missing access token")
	}
	refreshToken := strings.TrimSpace(account.GetCredential("refresh_token"))

	expiresAt := time.Time{}
	if ts := account.GetCredentialAsTime("expires_at"); ts != nil {
		expiresAt = ts.UTC()
	}

	s.backend.SetAccountToken(accountKey, accessToken, refreshToken, expiresAt)
	availableCredits, minimumCreditAmount := resolveLSPoolModelCreditsState(account)
	s.backend.SetAccountModelCredits(accountKey, account.IsOveragesEnabled(), availableCredits, minimumCreditAmount)

	proxyURL := ""
	if account.Proxy != nil {
		proxyURL = account.Proxy.URL()
	}

	if _, err := s.backend.GetOrCreate(accountKey, "", proxyURL); err != nil {
		return fmt.Errorf("get or create ls worker: %w", err)
	}
	return nil
}

func (s *LSPoolBootstrapService) bootstrapConcurrency() int {
	parallelism := defaultLSPoolBootstrapConcurrency
	if s.cfg != nil && s.cfg.Gateway.AntigravityLSWorker.MaxActive > 0 && s.cfg.Gateway.AntigravityLSWorker.MaxActive < parallelism {
		parallelism = s.cfg.Gateway.AntigravityLSWorker.MaxActive
	}
	if parallelism < 1 {
		return 1
	}
	return parallelism
}

func shouldBootstrapLSPoolAccount(account *Account, now time.Time) bool {
	if account == nil {
		return false
	}
	if account.Platform != PlatformAntigravity {
		return false
	}
	if account.Type != AccountTypeOAuth {
		return false
	}
	if account.Status != StatusActive || !account.Schedulable {
		return false
	}
	if account.AutoPauseOnExpired && account.ExpiresAt != nil && !now.Before(*account.ExpiresAt) {
		return false
	}
	if strings.TrimSpace(account.GetCredential("access_token")) == "" {
		return false
	}
	return strings.TrimSpace(account.GetCredential("project_id")) != ""
}