package provider

import (
	"bufio"
	"bytes"
	"context"
	"crypto/hmac"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"os"
	"strconv"
	"strings"
	"sync"
	"time"

	"orchestra/internal/domain"
)

type Sink interface{ Append(domain.Event) error }
type Provider interface {
	Ingest(io.Reader, Sink) (int, error)
}
type Reflector interface{ Reflect(domain.Event) error }
type TaskReflector interface {
	ReflectTask(domain.Task, domain.Event) error
}

type TaskLookup interface {
	Task(string) (domain.Task, bool)
}

// ReflectingSink preserves the append-first rule while asynchronously
// reflecting terminal state to an external provider. Reflection failures are
// returned to the caller so the supervisor can retry and surface health.
type ReflectingSink struct {
	Sink      Sink
	Tasks     TaskLookup
	Reflector TaskReflector
}

func (s ReflectingSink) Append(e domain.Event) error {
	if err := s.Sink.Append(e); err != nil {
		return err
	}
	if s.Reflector == nil || s.Tasks == nil {
		return nil
	}
	if t, ok := s.Tasks.Task(e.TaskID); ok {
		return s.Reflector.ReflectTask(t, e)
	}
	return nil
}

type Health struct {
	Name      string    `json:"name"`
	Running   bool      `json:"running"`
	LastError string    `json:"last_error,omitempty"`
	UpdatedAt time.Time `json:"updated_at"`
}

// Supervise restarts a provider loop with bounded backoff and exposes its
// current health. The loop exits only when its context is cancelled.
type Supervisor struct {
	Name    string
	Run     func(context.Context) error
	Backoff time.Duration
	mu      sync.RWMutex
	health  Health
}

func (s *Supervisor) Start(ctx context.Context) {
	if s.Backoff <= 0 {
		s.Backoff = time.Second
	}
	s.mu.Lock()
	s.health = Health{Name: s.Name, Running: true, UpdatedAt: time.Now().UTC()}
	s.mu.Unlock()
	go func() {
		for {
			err := s.Run(ctx)
			if ctx.Err() != nil {
				s.mu.Lock()
				s.health.Running = false
				s.health.UpdatedAt = time.Now().UTC()
				s.mu.Unlock()
				return
			}
			s.mu.Lock()
			s.health.LastError = errString(err)
			s.health.UpdatedAt = time.Now().UTC()
			s.mu.Unlock()
			t := time.NewTimer(s.Backoff)
			select {
			case <-ctx.Done():
				t.Stop()
				return
			case <-t.C:
			}
		}
	}()
}

func errString(err error) string {
	if err == nil {
		return "provider stopped"
	}
	return err.Error()
}
func (s *Supervisor) Health() Health { s.mu.RLock(); defer s.mu.RUnlock(); return s.health }

type JSONL struct{ Source string }

func (j JSONL) Ingest(r io.Reader, sink Sink) (int, error) {
	sc := bufio.NewScanner(r)
	sc.Buffer(make([]byte, 64*1024), 4*1024*1024)
	count, line := 0, 0
	for sc.Scan() {
		line++
		raw := bytes.TrimSpace(sc.Bytes())
		if len(raw) == 0 {
			continue
		}
		var p map[string]any
		if err := json.Unmarshal(raw, &p); err != nil {
			return count, fmt.Errorf("line %d: %w", line, err)
		}
		if j.Source != "" {
			p["source"] = j.Source
		}
		if err := domain.ValidateCreated(p); err != nil {
			return count, fmt.Errorf("line %d: %w", line, err)
		}
		b, _ := json.Marshal(p)
		if err := sink.Append(domain.Event{ID: domain.NewID(), Type: "TaskCreated", TaskID: domain.NewID(), Version: 1, Payload: b}); err != nil {
			return count, fmt.Errorf("line %d: %w", line, err)
		}
		count++
	}
	return count, sc.Err()
}

// JSONLWatcher ingests only newly appended lines and tolerates file rotation.
type JSONLWatcher struct {
	Path     string
	Interval time.Duration
	Provider JSONL
}

func (w JSONLWatcher) Run(ctx context.Context, sink Sink) error {
	if w.Interval <= 0 {
		w.Interval = time.Second
	}
	if w.Provider.Source == "" {
		w.Provider.Source = "jsonl"
	}
	var offset int64
	for {
		f, err := os.Open(w.Path)
		if err != nil {
			if errors.Is(err, os.ErrNotExist) {
				select {
				case <-ctx.Done():
					return ctx.Err()
				case <-time.After(w.Interval):
					continue
				}
			}
			return err
		}
		if st, _ := f.Stat(); st.Size() < offset {
			offset = 0
		}
		if _, err = f.Seek(offset, io.SeekStart); err != nil {
			f.Close()
			return err
		}
		n, err := w.Provider.Ingest(f, sink)
		pos, _ := f.Seek(0, io.SeekCurrent)
		offset = pos
		f.Close()
		if err != nil {
			return err
		}
		_ = n
		select {
		case <-ctx.Done():
			return ctx.Err()
		case <-time.After(w.Interval):
		}
	}
}

type Gitea struct {
	BaseURL, Token, WebhookSecret, Owner, Repo string
	Client                                     *http.Client
}
type giteaIssue struct {
	Number int    `json:"number"`
	Title  string `json:"title"`
	Body   string `json:"body"`
	State  string `json:"state"`
	Labels []struct {
		Name string `json:"name"`
	} `json:"labels"`
}
type giteaWebhook struct {
	Action     string     `json:"action"`
	Issue      giteaIssue `json:"issue"`
	Repository struct {
		FullName string `json:"full_name"`
	} `json:"repository"`
}

func (g Gitea) client() *http.Client {
	if g.Client != nil {
		return g.Client
	}
	return http.DefaultClient
}
func (g Gitea) event(issue giteaIssue, source, project string) domain.Event {
	caps := []string{}
	for _, l := range issue.Labels {
		caps = append(caps, l.Name)
	}
	p := map[string]any{"source": source, "external_id": strconv.Itoa(issue.Number), "project": project, "title": issue.Title, "capability": caps}
	b, _ := json.Marshal(p)
	return domain.Event{ID: domain.NewID(), TaskID: domain.NewID(), Type: "TaskCreated", Version: 1, Payload: b}
}
func (g Gitea) IngestWebhook(body []byte, signature string, sink Sink) error {
	if !validSignature(body, signature, g.WebhookSecret) {
		return errors.New("invalid webhook signature")
	}
	var h giteaWebhook
	if err := json.Unmarshal(body, &h); err != nil {
		return err
	}
	if h.Action == "closed" || h.Action == "deleted" {
		return nil
	}
	project := g.Repo
	if h.Repository.FullName != "" {
		project = h.Repository.FullName
	}
	return sink.Append(g.event(h.Issue, "gitea", project))
}
func validSignature(body []byte, got, secret string) bool {
	if secret == "" || got == "" {
		return false
	}
	got = strings.TrimPrefix(got, "sha256=")
	mac := hmac.New(sha256.New, []byte(secret))
	mac.Write(body)
	want := hex.EncodeToString(mac.Sum(nil))
	return hmac.Equal([]byte(strings.ToLower(got)), []byte(want))
}

// WebhookHandler authenticates the request before decoding or appending it.
func (g Gitea) WebhookHandler(sink Sink) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodPost {
			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
			return
		}
		body, err := io.ReadAll(io.LimitReader(r.Body, 4<<20))
		if err != nil {
			http.Error(w, "invalid body", http.StatusBadRequest)
			return
		}
		if err = g.IngestWebhook(body, r.Header.Get("X-Gitea-Signature"), sink); err != nil {
			http.Error(w, err.Error(), http.StatusUnauthorized)
			return
		}
		w.WriteHeader(http.StatusAccepted)
	})
}
func (g Gitea) Poll(ctx context.Context, sink Sink) (int, error) {
	u := strings.TrimRight(g.BaseURL, "/") + "/api/v1/repos/" + g.Owner + "/" + g.Repo + "/issues?state=open"
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u, nil)
	if err != nil {
		return 0, err
	}
	if g.Token != "" {
		req.Header.Set("Authorization", "token "+g.Token)
	}
	resp, err := g.client().Do(req)
	if err != nil {
		return 0, err
	}
	defer resp.Body.Close()
	if resp.StatusCode/100 != 2 {
		return 0, fmt.Errorf("gitea poll: %s", resp.Status)
	}
	var issues []giteaIssue
	if err = json.NewDecoder(resp.Body).Decode(&issues); err != nil {
		return 0, err
	}
	for _, i := range issues {
		if err := sink.Append(g.event(i, "gitea", g.Repo)); err != nil {
			return 0, err
		}
	}
	return len(issues), nil
}
func (g Gitea) Reflect(e domain.Event) error {
	if e.Type != "TaskCompleted" && e.Type != "TaskBlocked" && e.Type != "TaskFailed" {
		return nil
	}
	var p struct {
		ExternalID string `json:"external_id"`
	}
	_ = json.Unmarshal(e.Payload, &p)
	if p.ExternalID == "" {
		return nil
	}
	u := strings.TrimRight(g.BaseURL, "/") + "/api/v1/repos/" + g.Owner + "/" + g.Repo + "/issues/" + p.ExternalID
	body, _ := json.Marshal(map[string]any{"state": "closed"})
	req, err := http.NewRequest(http.MethodPatch, u, bytes.NewReader(body))
	if err != nil {
		return err
	}
	req.Header.Set("Content-Type", "application/json")
	if g.Token != "" {
		req.Header.Set("Authorization", "token "+g.Token)
	}
	resp, err := g.client().Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	if resp.StatusCode/100 != 2 {
		return fmt.Errorf("gitea reflect: %s", resp.Status)
	}
	return nil
}

// ReflectTask is the preferred reflection entry point because lifecycle events
// identify the internal task, while the external key lives on the task.
func (g Gitea) ReflectTask(task domain.Task, e domain.Event) error {
	if e.Type != "TaskCompleted" && e.Type != "TaskBlocked" && e.Type != "TaskFailed" {
		return nil
	}
	e.Payload, _ = json.Marshal(map[string]any{"external_id": task.ExternalID})
	return g.Reflect(e)
}