package tmsync

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
	"time"

	"task/internal/project"
	"task/internal/ticket"
	"task/internal/ytsync"
)

// Result reuses ytsync.Result for consistent CLI/UI messaging.
type Result = ytsync.Result

// Syncer syncs a local project with a remote tm_server project.
type Syncer struct {
	Store     ticket.Store
	TimeStore ticket.TimeStore
	HTTP      *http.Client
}

func (s *Syncer) http() *http.Client {
	if s.HTTP != nil {
		return s.HTTP
	}
	return http.DefaultClient
}

// NeedsPush reports whether a local ticket should be pushed to task-master.
func NeedsPush(t ticket.Ticket) bool {
	if t.ExternalID == "" {
		return true
	}
	if t.Source != ticket.SourceTaskMaster {
		return false
	}
	if t.SyncedAt.IsZero() {
		return true
	}
	return t.UpdatedAt.After(t.SyncedAt)
}

// Pull imports remote tickets/time into localProjectID.
func (s *Syncer) Pull(ctx context.Context, localProjectID string, tm project.TaskMaster) (Result, error) {
	if !tm.Configured() {
		return Result{}, fmt.Errorf("taskmaster not configured for project %s", localProjectID)
	}
	if s.Store == nil {
		return Result{}, fmt.Errorf("ticket store required")
	}
	remote, err := s.listTickets(ctx, tm)
	if err != nil {
		return Result{}, err
	}
	existing, err := s.Store.List(localProjectID)
	if err != nil {
		return Result{}, err
	}
	byExt := map[string]ticket.Ticket{}
	for _, t := range existing {
		if t.ExternalID != "" {
			byExt[t.ExternalID] = t
		}
	}
	var res Result
	res.Total = len(remote)
	for _, rt := range remote {
		if rt.ID == "" {
			res.Skipped++
			continue
		}
		extURL := strings.TrimRight(tm.BaseURL, "/") + "/#/ticket/" + rt.ID
		if prev, ok := byExt[rt.ID]; ok {
			if NeedsPush(prev) {
				res.Skipped++
				continue
			}
			next := prev
			next.Title = rt.Title
			next.Description = rt.Description
			next.Status = rt.Status
			next.Source = ticket.SourceTaskMaster
			next.ExternalURL = extURL
			next.Number = rt.Number
			next.Key = rt.Key
			if sameFields(prev, next) {
				_ = s.Store.MarkSynced(prev.ID)
				res.Skipped++
				continue
			}
			if err := s.Store.Update(next); err != nil {
				return res, err
			}
			_ = s.Store.MarkSynced(next.ID)
			res.Updated++
			continue
		}
		now := time.Now().UTC()
		_, err := s.Store.Create(ticket.Ticket{
			Title: rt.Title, Description: rt.Description, Status: rt.Status,
			ProjectID: localProjectID, Source: ticket.SourceTaskMaster,
			ExternalID: rt.ID, ExternalURL: extURL,
			Number: rt.Number, Key: rt.Key,
			CreatedAt: now, UpdatedAt: now, SyncedAt: now,
		})
		if err != nil {
			return res, err
		}
		res.Created++
	}
	if err := s.pullTime(ctx, tm, localProjectID, &res); err != nil {
		return res, err
	}
	return res, nil
}

// Push sends dirty local tickets/time to the remote project.
func (s *Syncer) Push(ctx context.Context, localProjectID string, tm project.TaskMaster) (Result, error) {
	if !tm.Configured() {
		return Result{}, fmt.Errorf("taskmaster not configured for project %s", localProjectID)
	}
	if s.Store == nil {
		return Result{}, fmt.Errorf("ticket store required")
	}
	existing, err := s.Store.List(localProjectID)
	if err != nil {
		return Result{}, err
	}
	var res Result
	for _, t := range existing {
		if !NeedsPush(t) {
			res.Skipped++
			continue
		}
		res.Total++
		if t.ExternalID == "" {
			created, err := s.createRemote(ctx, tm, t)
			if err != nil {
				return res, err
			}
			t.ExternalID = created.ID
			t.Number = created.Number
			t.Key = created.Key
			t.Source = ticket.SourceTaskMaster
			t.ExternalURL = strings.TrimRight(tm.BaseURL, "/") + "/#/ticket/" + created.ID
			if err := s.Store.Update(t); err != nil {
				return res, err
			}
			_ = s.Store.MarkSynced(t.ID)
			res.Created++
			res.Pushed++
			continue
		}
		if err := s.patchRemote(ctx, tm, t); err != nil {
			return res, err
		}
		_ = s.Store.MarkSynced(t.ID)
		res.Updated++
		res.Pushed++
	}
	if err := s.pushTime(ctx, tm, localProjectID, &res); err != nil {
		return res, err
	}
	return res, nil
}

func sameFields(a, b ticket.Ticket) bool {
	return a.Title == b.Title && a.Description == b.Description && a.Status == b.Status &&
		a.Key == b.Key && a.Number == b.Number
}

func (s *Syncer) listTickets(ctx context.Context, tm project.TaskMaster) ([]ticket.Ticket, error) {
	var out []ticket.Ticket
	err := s.doJSON(ctx, tm, http.MethodGet, "/projects/"+tm.ProjectID+"/tickets", nil, &out)
	return out, err
}

func (s *Syncer) createRemote(ctx context.Context, tm project.TaskMaster, t ticket.Ticket) (ticket.Ticket, error) {
	body := map[string]any{
		"title": t.Title, "description": t.Description, "status": t.Status,
	}
	var created ticket.Ticket
	err := s.doJSON(ctx, tm, http.MethodPost, "/projects/"+tm.ProjectID+"/tickets", body, &created)
	return created, err
}

func (s *Syncer) patchRemote(ctx context.Context, tm project.TaskMaster, t ticket.Ticket) error {
	body := map[string]any{
		"title": t.Title, "description": t.Description, "status": t.Status,
	}
	return s.doJSON(ctx, tm, http.MethodPatch,
		"/projects/"+tm.ProjectID+"/tickets/"+t.ExternalID, body, nil)
}

func (s *Syncer) pullTime(ctx context.Context, tm project.TaskMaster, localProjectID string, res *Result) error {
	if s.TimeStore == nil {
		return nil
	}
	var remote []ticket.TimeEntry
	if err := s.doJSON(ctx, tm, http.MethodGet, "/projects/"+tm.ProjectID+"/time", nil, &remote); err != nil {
		return err
	}
	localTickets, err := s.Store.List(localProjectID)
	if err != nil {
		return err
	}
	localByExt := map[string]ticket.Ticket{}
	for _, t := range localTickets {
		if t.ExternalID != "" {
			localByExt[t.ExternalID] = t
		}
	}
	existing, err := s.TimeStore.List()
	if err != nil {
		return err
	}
	have := map[string]bool{}
	for _, e := range existing {
		if e.ExternalID != "" {
			have[e.ExternalID] = true
		}
	}
	for _, e := range remote {
		if e.ID == "" || have[e.ID] {
			continue
		}
		lt, ok := localByExt[e.TicketID]
		if !ok {
			continue
		}
		_, err := s.TimeStore.Create(ticket.TimeEntry{
			TicketID: lt.ID, ProjectID: localProjectID,
			Start: e.Start, End: e.End, Duration: e.Duration,
			Source: ticket.SourceTaskMaster, Note: e.Note, ExternalID: e.ID,
		})
		if err != nil {
			return err
		}
		res.TimePulled++
	}
	return nil
}

func (s *Syncer) pushTime(ctx context.Context, tm project.TaskMaster, localProjectID string, res *Result) error {
	if s.TimeStore == nil {
		return nil
	}
	tickets, err := s.Store.List(localProjectID)
	if err != nil {
		return err
	}
	byID := map[string]ticket.Ticket{}
	for _, t := range tickets {
		byID[t.ID] = t
	}
	entries, err := s.TimeStore.List()
	if err != nil {
		return err
	}
	for _, e := range entries {
		if e.ProjectID != localProjectID || e.ExternalID != "" {
			continue
		}
		t, ok := byID[e.TicketID]
		if !ok || t.ExternalID == "" {
			continue
		}
		body := map[string]any{
			"ticketId":   t.ExternalID,
			"durationNs": int64(e.Duration),
			"note":       e.Note,
			"source":     e.Source,
		}
		var created ticket.TimeEntry
		if err := s.doJSON(ctx, tm, http.MethodPost, "/projects/"+tm.ProjectID+"/time", body, &created); err != nil {
			return err
		}
		e.ExternalID = created.ID
		if err := s.TimeStore.Update(e); err != nil {
			return err
		}
		res.TimePushed++
	}
	return nil
}

func (s *Syncer) doJSON(ctx context.Context, tm project.TaskMaster, method, path string, body any, dest any) error {
	var rdr io.Reader
	if body != nil {
		data, err := json.Marshal(body)
		if err != nil {
			return err
		}
		rdr = bytes.NewReader(data)
	}
	url := strings.TrimRight(strings.TrimSpace(tm.BaseURL), "/") + "/api/v1" + path
	req, err := http.NewRequestWithContext(ctx, method, url, rdr)
	if err != nil {
		return err
	}
	req.Header.Set("Authorization", "Bearer "+tm.Token)
	req.Header.Set("Accept", "application/json")
	if body != nil {
		req.Header.Set("Content-Type", "application/json")
	}
	resp, err := s.http().Do(req)
	if err != nil {
		return fmt.Errorf("taskmaster: %w", err)
	}
	defer resp.Body.Close()
	data, err := io.ReadAll(resp.Body)
	if err != nil {
		return err
	}
	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		var eresp struct {
			Error string `json:"error"`
		}
		_ = json.Unmarshal(data, &eresp)
		msg := eresp.Error
		if msg == "" {
			msg = string(data)
		}
		return fmt.Errorf("taskmaster: %s: %s", resp.Status, msg)
	}
	if dest == nil || len(data) == 0 {
		return nil
	}
	return json.Unmarshal(data, dest)
}