package orchestrator

import (
	"context"
	"errors"
	"log/slog"
	"sync"

	"github.com/vasyansk/imap-copier/internal/crypto"
	"github.com/vasyansk/imap-copier/internal/imapx"
	"github.com/vasyansk/imap-copier/internal/store"
	"github.com/vasyansk/imap-copier/internal/wshub"
)

var ErrNotTested = errors.New("accounts not fully tested")
var ErrAlreadyRunning = errors.New("task already running")

type Orchestrator struct {
	store       *store.Store
	hub         *wshub.Hub
	encKey      []byte
	concurrency int
}

func New(s *store.Store, hub *wshub.Hub, encKey []byte, concurrency int) *Orchestrator {
	return &Orchestrator{store: s, hub: hub, encKey: encKey, concurrency: concurrency}
}

func gateOK(accs []store.Account) bool {
	if len(accs) == 0 {
		return false
	}
	for _, a := range accs {
		if a.TestSrcStatus != "ok" || a.TestDstStatus != "ok" {
			return false
		}
	}
	return true
}

func (o *Orchestrator) endpoints(ctx context.Context, task store.Task) (imapx.Endpoint, imapx.Endpoint, error) {
	src, err := o.store.GetEndpoint(ctx, task.SrcEndpointID)
	if err != nil {
		return imapx.Endpoint{}, imapx.Endpoint{}, err
	}
	dst, err := o.store.GetEndpoint(ctx, task.DstEndpointID)
	if err != nil {
		return imapx.Endpoint{}, imapx.Endpoint{}, err
	}
	toEP := func(e store.Endpoint) imapx.Endpoint {
		return imapx.Endpoint{Host: e.Host, Port: e.Port, TLSMode: e.TLSMode}
	}
	return toEP(src), toEP(dst), nil
}

func (o *Orchestrator) TestAccounts(ctx context.Context, taskID int64) error {
	task, err := o.store.GetTask(ctx, taskID)
	if err != nil {
		return err
	}
	srcEP, dstEP, err := o.endpoints(ctx, task)
	if err != nil {
		return err
	}
	accs, err := o.store.ListAccountsByTask(ctx, taskID)
	if err != nil {
		return err
	}
	for _, a := range accs {
		o.testSide(ctx, srcEP, a.ID, "src", a.SrcLogin, a.SrcPassEnc, taskID)
		o.testSide(ctx, dstEP, a.ID, "dst", a.DstLogin, a.DstPassEnc, taskID)
	}
	return nil
}

func (o *Orchestrator) testSide(ctx context.Context, ep imapx.Endpoint, accID int64, side, login, passEnc string, taskID int64) {
	status := "ok"
	pass, err := crypto.Decrypt(o.encKey, passEnc)
	if err == nil {
		_, err = imapx.TestLogin(ctx, ep, login, string(pass))
	}
	if err != nil {
		status = "fail"
		slog.Warn("account test failed", "account", accID, "side", side, "err", err)
	}
	_ = o.store.SetAccountTestStatus(ctx, accID, side, status)
	o.hub.Publish(wshub.Event{Type: "account_test", TaskID: taskID,
		Data: map[string]any{"account_id": accID, "side": side, "status": status}})
}

func (o *Orchestrator) Run(ctx context.Context, taskID int64) (int64, error) {
	task, err := o.store.GetTask(ctx, taskID)
	if err != nil {
		return 0, err
	}
	accs, err := o.store.ListAccountsByTask(ctx, taskID)
	if err != nil {
		return 0, err
	}
	if !gateOK(accs) {
		return 0, ErrNotTested
	}
	acquired, err := o.store.TryMarkTaskRunning(ctx, taskID)
	if err != nil {
		return 0, err
	}
	if !acquired {
		return 0, ErrAlreadyRunning
	}
	srcEP, dstEP, err := o.endpoints(ctx, task)
	if err != nil {
		_ = o.store.SetTaskStatus(ctx, taskID, "error")
		return 0, err
	}
	runID, err := o.store.CreateRun(ctx, taskID)
	if err != nil {
		_ = o.store.SetTaskStatus(ctx, taskID, "error")
		return 0, err
	}
	o.hub.Publish(wshub.Event{Type: "run_started", TaskID: taskID, Data: map[string]any{"run_id": runID}})

	go o.runAll(context.WithoutCancel(ctx), task, runID, accs, srcEP, dstEP)
	return runID, nil
}

func (o *Orchestrator) runAll(ctx context.Context, task store.Task, runID int64, accs []store.Account, srcEP, dstEP imapx.Endpoint) {
	var (
		mu                            sync.Mutex
		totCopied, totSkipped, totErr int64
	)
	sem := make(chan struct{}, o.concurrency)
	var wg sync.WaitGroup

	for _, a := range accs {
		wg.Add(1)
		sem <- struct{}{}
		go func(a store.Account) {
			defer wg.Done()
			defer func() { <-sem }()
			c, s, e := o.runAccount(ctx, task, runID, a, srcEP, dstEP)
			mu.Lock()
			totCopied += c
			totSkipped += s
			totErr += e
			mu.Unlock()
		}(a)
	}
	wg.Wait()

	status := "done"
	if totErr > 0 {
		status = "done_with_errors"
	}
	_ = o.store.FinishRun(ctx, runID, status, totCopied, totSkipped, totErr)
	_ = o.store.SetTaskStatus(ctx, task.ID, status)
	o.hub.Publish(wshub.Event{Type: "run_done", TaskID: task.ID,
		Data: map[string]any{"run_id": runID, "copied": totCopied, "skipped": totSkipped, "errors": totErr}})
}

func (o *Orchestrator) runAccount(ctx context.Context, task store.Task, runID int64, a store.Account, srcEP, dstEP imapx.Endpoint) (int64, int64, int64) {
	o.hub.Publish(wshub.Event{Type: "account_started", TaskID: task.ID, Data: map[string]any{"account_id": a.ID}})
	_ = o.store.SetAccountStatus(ctx, a.ID, "running")

	srcPass, err := crypto.Decrypt(o.encKey, a.SrcPassEnc)
	if err != nil {
		return o.accountFailed(ctx, task.ID, a.ID, err)
	}
	dstPass, err := crypto.Decrypt(o.encKey, a.DstPassEnc)
	if err != nil {
		return o.accountFailed(ctx, task.ID, a.ID, err)
	}

	src, err := imapx.Connect(ctx, srcEP)
	if err != nil {
		return o.accountFailed(ctx, task.ID, a.ID, err)
	}
	defer func() { _ = src.Logout().Wait() }()
	if err := src.Login(a.SrcLogin, string(srcPass)).Wait(); err != nil {
		return o.accountFailed(ctx, task.ID, a.ID, err)
	}
	dst, err := imapx.Connect(ctx, dstEP)
	if err != nil {
		return o.accountFailed(ctx, task.ID, a.ID, err)
	}
	defer func() { _ = dst.Logout().Wait() }()
	if err := dst.Login(a.DstLogin, string(dstPass)).Wait(); err != nil {
		return o.accountFailed(ctx, task.ID, a.ID, err)
	}

	folders, err := imapx.ListFolders(src)
	if err != nil {
		return o.accountFailed(ctx, task.ID, a.ID, err)
	}

	var copied, skipped, errs int64
	deps := imapx.CopyDeps{
		IsMigrated:   func(k string) (bool, error) { return o.store.IsMigrated(ctx, a.ID, k) },
		MarkMigrated: func(folder, k string) error { return o.store.MarkMigrated(ctx, a.ID, folder, k) },
		OnProgress: func(c, s int) {
			o.hub.Publish(wshub.Event{Type: "progress", TaskID: task.ID,
				Data: map[string]any{"account_id": a.ID, "copied": c, "skipped": s}})
		},
	}
	for _, folder := range folders {
		dstFolder := folder
		if m, ok := task.FolderMapping[folder]; ok {
			dstFolder = m
		}
		res, err := imapx.CopyFolder(ctx, src, dst, folder, dstFolder, deps)
		if err != nil {
			slog.Warn("folder copy error", "account", a.ID, "folder", folder, "err", err)
			errs++
		}
		copied += int64(res.Copied)
		skipped += int64(res.Skipped)
		errs += int64(res.Errors)
		_ = o.store.IncAccountCounters(ctx, a.ID, int64(res.Copied), int64(res.Skipped), int64(res.Errors))
	}
	_ = o.store.SetAccountStatus(ctx, a.ID, "done")
	o.hub.Publish(wshub.Event{Type: "account_done", TaskID: task.ID,
		Data: map[string]any{"account_id": a.ID, "copied": copied, "skipped": skipped, "errors": errs}})
	slog.Info("account copied", "account", a.ID, "copied", copied, "skipped", skipped, "errors", errs)
	return copied, skipped, errs
}

func (o *Orchestrator) accountFailed(ctx context.Context, taskID, accID int64, err error) (int64, int64, int64) {
	slog.Error("account failed", "account", accID, "err", err)
	_ = o.store.SetAccountStatus(ctx, accID, "error")
	o.hub.Publish(wshub.Event{Type: "error", TaskID: taskID,
		Data: map[string]any{"account_id": accID, "error": err.Error()}})
	return 0, 0, 1
}