package api

import (
	"encoding/json"
	"errors"
	"fmt"
	"net/http"
	"strconv"
	"strings"
	"time"

	"git.amiirkhl.ir/starcoach-hackathon/zarinpal-analytics-backend/internal/coach"
	"git.amiirkhl.ir/starcoach-hackathon/zarinpal-analytics-backend/internal/insight"
)

func (s *Server) growthCoachDashboard(w http.ResponseWriter, r *http.Request) {
	if s.coach == nil {
		s.problem(w, r, 404, "RESOURCE_NOT_FOUND", "Resource not found")
		return
	}
	terminalID, ok := onlyTerminalQuery(r)
	if !ok {
		s.problem(w, r, 422, "VALIDATION_FAILED", "Only terminalId is accepted")
		return
	}
	result, err := s.coach.Dashboard(r.Context(), sessionFrom(r.Context()).MerchantID, terminalID)
	if errors.Is(err, coach.ErrUnknownTerminal) {
		s.problem(w, r, 404, "RESOURCE_NOT_FOUND", "Resource not found")
		return
	}
	if err != nil {
		s.logger.Error("loading growth coach failed", "error", err)
		s.problem(w, r, 503, "GROWTH_COACH_UNAVAILABLE", "Growth coach unavailable")
		return
	}
	s.writeJSON(w, 200, result)
}

func (s *Server) growthCoachProfile(w http.ResponseWriter, r *http.Request) {
	if s.coach == nil {
		s.problem(w, r, 404, "RESOURCE_NOT_FOUND", "Resource not found")
		return
	}
	result, err := s.coach.Profile(r.Context(), sessionFrom(r.Context()).MerchantID, r.PathValue("terminalId"))
	if errors.Is(err, coach.ErrNotFound) || errors.Is(err, coach.ErrUnknownTerminal) {
		s.problem(w, r, 404, "RESOURCE_NOT_FOUND", "Resource not found")
		return
	}
	if err != nil {
		s.problem(w, r, 503, "GROWTH_COACH_UNAVAILABLE", "Growth coach unavailable")
		return
	}
	s.writeJSON(w, 200, result)
}

func (s *Server) saveGrowthCoachProfile(w http.ResponseWriter, r *http.Request) {
	if s.coach == nil {
		s.problem(w, r, 404, "RESOURCE_NOT_FOUND", "Resource not found")
		return
	}
	key := r.Header.Get("Idempotency-Key")
	if !validIdempotencyKey(key) {
		s.problem(w, r, 422, "VALIDATION_FAILED", "A valid Idempotency-Key is required")
		return
	}
	var input coach.ProfileInput
	if decodeStrictJSON(w, r, &input) != nil {
		s.problem(w, r, 422, "VALIDATION_FAILED", "Invalid business profile")
		return
	}
	session := sessionFrom(r.Context())
	profile, jobs, cached, err := s.coach.SaveProfile(r.Context(), session.MerchantID, session.UserID, r.PathValue("terminalId"), key, input)
	switch {
	case errors.Is(err, coach.ErrUnknownTerminal):
		s.problem(w, r, 404, "RESOURCE_NOT_FOUND", "Resource not found")
		return
	case errors.Is(err, coach.ErrIdempotencyConflict):
		s.problem(w, r, 409, "IDEMPOTENCY_CONFLICT", "Idempotency key was already used")
		return
	case err != nil:
		s.problem(w, r, 422, "VALIDATION_FAILED", "Invalid business profile")
		return
	}
	status := http.StatusCreated
	if cached {
		status = http.StatusOK
	}
	if jobs == nil {
		jobs = []coach.Job{}
	}
	pageJobs := []insight.Job{}
	if !cached && s.insights != nil {
		for _, module := range []insight.Module{insight.ModuleOverview, insight.ModulePayments, insight.ModuleFees, insight.ModulePeers, insight.ModuleTransactions, insight.ModuleGrowth} {
			job, _, enqueueErr := s.insights.Enqueue(r.Context(), session.MerchantID, r.PathValue("terminalId"), module, "PROFILE:"+profile.ProfileID)
			if enqueueErr != nil {
				s.logger.Error("profile-triggered page insight scheduling failed", "error", enqueueErr, "module", module)
				continue
			}
			pageJobs = append(pageJobs, job)
		}
	}
	s.writeJSON(w, status, map[string]any{"profile": profile, "generationJobs": jobs, "pageInsightJobs": pageJobs})
}

func (s *Server) refreshGrowthCoach(w http.ResponseWriter, r *http.Request) {
	if s.coach == nil {
		s.problem(w, r, 404, "RESOURCE_NOT_FOUND", "Resource not found")
		return
	}
	key := r.Header.Get("Idempotency-Key")
	if !validIdempotencyKey(key) {
		s.problem(w, r, 422, "VALIDATION_FAILED", "A valid Idempotency-Key is required")
		return
	}
	var input coach.RefreshInput
	if decodeStrictJSON(w, r, &input) != nil || input.Validate() != nil {
		s.problem(w, r, 422, "VALIDATION_FAILED", "Invalid growth coach refresh cadence")
		return
	}
	job, cached, err := s.coach.Refresh(r.Context(), sessionFrom(r.Context()).MerchantID, r.PathValue("terminalId"), key, input)
	if errors.Is(err, coach.ErrNotFound) || errors.Is(err, coach.ErrUnknownTerminal) {
		s.problem(w, r, 404, "RESOURCE_NOT_FOUND", "Resource not found")
		return
	}
	if errors.Is(err, coach.ErrIdempotencyConflict) {
		s.problem(w, r, 409, "IDEMPOTENCY_CONFLICT", "Idempotency key was already used")
		return
	}
	var limit *coach.RefreshLimitError
	if errors.As(err, &limit) {
		retryAfter := max(0, int(time.Until(limit.NextRefreshAt).Seconds()))
		w.Header().Set("Retry-After", strconv.Itoa(retryAfter))
		w.Header().Set("Content-Type", "application/problem+json")
		w.WriteHeader(http.StatusTooManyRequests)
		_ = json.NewEncoder(w).Encode(map[string]any{"type": "https://zarinpal.amiirkhl.ir/docs/errors/refresh-limited", "title": "Too Many Requests", "status": 429, "code": "REFRESH_LIMITED", "detail": "Weekly suggestion refresh limit reached", "instance": r.URL.Path, "requestId": w.Header().Get("X-Request-ID"), "nextRefreshAt": limit.NextRefreshAt})
		return
	}
	if err != nil {
		s.problem(w, r, 503, "GROWTH_COACH_UNAVAILABLE", "Growth coach unavailable")
		return
	}
	status := http.StatusAccepted
	if cached {
		status = http.StatusOK
	}
	w.Header().Set("Location", "/api/v1/growth-coach/refreshes/"+job.JobID)
	s.writeJSON(w, status, job)
}

func (s *Server) growthCoachPlans(w http.ResponseWriter, r *http.Request) {
	if s.coach == nil {
		s.problem(w, r, 404, "RESOURCE_NOT_FOUND", "Resource not found")
		return
	}
	terminalID, ok := onlyTerminalQuery(r)
	if !ok {
		s.problem(w, r, 422, "VALIDATION_FAILED", "Only terminalId is accepted")
		return
	}
	result, err := s.coach.Plans(r.Context(), sessionFrom(r.Context()).MerchantID, terminalID)
	if errors.Is(err, coach.ErrUnknownTerminal) {
		s.problem(w, r, 404, "RESOURCE_NOT_FOUND", "Resource not found")
		return
	}
	if err != nil {
		s.problem(w, r, 503, "GROWTH_COACH_UNAVAILABLE", "Growth coach unavailable")
		return
	}
	s.writeJSON(w, 200, map[string]any{"plans": result})
}
func (s *Server) growthCoachActions(w http.ResponseWriter, r *http.Request) {
	if s.coach == nil {
		s.problem(w, r, 404, "RESOURCE_NOT_FOUND", "Resource not found")
		return
	}
	terminalID, ok := onlyTerminalQuery(r)
	if !ok {
		s.problem(w, r, 422, "VALIDATION_FAILED", "Only terminalId is accepted")
		return
	}
	result, err := s.coach.Actions(r.Context(), sessionFrom(r.Context()).MerchantID, terminalID)
	if errors.Is(err, coach.ErrUnknownTerminal) {
		s.problem(w, r, 404, "RESOURCE_NOT_FOUND", "Resource not found")
		return
	}
	if err != nil {
		s.problem(w, r, 503, "GROWTH_COACH_UNAVAILABLE", "Growth coach unavailable")
		return
	}
	s.writeJSON(w, 200, map[string]any{"actions": result})
}

func (s *Server) growthCoachGoals(w http.ResponseWriter, r *http.Request) {
	if s.coach == nil {
		s.problem(w, r, 404, "RESOURCE_NOT_FOUND", "Resource not found")
		return
	}
	terminalID, ok := onlyTerminalQuery(r)
	if !ok {
		s.problem(w, r, 422, "VALIDATION_FAILED", "Only terminalId is accepted")
		return
	}
	goals, err := s.coach.Goals(r.Context(), sessionFrom(r.Context()).MerchantID, terminalID)
	if errors.Is(err, coach.ErrUnknownTerminal) {
		s.problem(w, r, 404, "RESOURCE_NOT_FOUND", "Resource not found")
		return
	}
	if err != nil {
		s.problem(w, r, 503, "GROWTH_COACH_UNAVAILABLE", "Growth coach unavailable")
		return
	}
	s.writeJSON(w, 200, map[string]any{"goals": goals})
}

func (s *Server) transitionGrowthCoachSubtask(w http.ResponseWriter, r *http.Request) {
	if !requireMutationKey(s, w, r) {
		return
	}
	var input coach.SubtaskTransitionInput
	if decodeStrictJSON(w, r, &input) != nil {
		s.problem(w, r, 422, "VALIDATION_FAILED", "Invalid subtask transition")
		return
	}
	session := sessionFrom(r.Context())
	result, err := s.coach.TransitionSubtask(r.Context(), session.MerchantID, session.UserID, r.PathValue("goalId"), r.PathValue("subtaskId"), r.Header.Get("Idempotency-Key"), input)
	switch {
	case errors.Is(err, coach.ErrNotFound):
		s.problem(w, r, 404, "RESOURCE_NOT_FOUND", "Resource not found")
	case errors.Is(err, coach.ErrInvalidTransition):
		s.problem(w, r, 409, "INVALID_TRANSITION", "This subtask transition is not allowed")
	case errors.Is(err, coach.ErrIdempotencyConflict):
		s.problem(w, r, 409, "IDEMPOTENCY_CONFLICT", "Idempotency key was already used")
	case err != nil:
		s.problem(w, r, 503, "GROWTH_COACH_UNAVAILABLE", "Growth coach unavailable")
	default:
		s.writeJSON(w, 200, result)
	}
}

func (s *Server) decideGrowthCoachDeadlineProposal(w http.ResponseWriter, r *http.Request) {
	if !requireMutationKey(s, w, r) {
		return
	}
	var input coach.DeadlineDecisionInput
	if decodeStrictJSON(w, r, &input) != nil {
		s.problem(w, r, 422, "VALIDATION_FAILED", "Invalid deadline decision")
		return
	}
	session := sessionFrom(r.Context())
	result, err := s.coach.DecideDeadlineProposal(r.Context(), session.MerchantID, session.UserID, r.PathValue("proposalId"), r.Header.Get("Idempotency-Key"), input)
	switch {
	case errors.Is(err, coach.ErrNotFound):
		s.problem(w, r, 404, "RESOURCE_NOT_FOUND", "Resource not found")
	case errors.Is(err, coach.ErrInvalidTransition):
		s.problem(w, r, 409, "INVALID_TRANSITION", "This deadline decision is not allowed")
	case errors.Is(err, coach.ErrIdempotencyConflict):
		s.problem(w, r, 409, "IDEMPOTENCY_CONFLICT", "Idempotency key was already used")
	case err != nil:
		s.problem(w, r, 503, "GROWTH_COACH_UNAVAILABLE", "Growth coach unavailable")
	default:
		s.writeJSON(w, 200, result)
	}
}

func (s *Server) decideGrowthCoachRecommendation(w http.ResponseWriter, r *http.Request) {
	if !requireMutationKey(s, w, r) {
		return
	}
	var input coach.DecisionInput
	if decodeStrictJSON(w, r, &input) != nil {
		s.problem(w, r, 422, "VALIDATION_FAILED", "Invalid recommendation decision")
		return
	}
	session := sessionFrom(r.Context())
	action, err := s.coach.DecideRecommendation(r.Context(), session.MerchantID, session.UserID, r.PathValue("id"), r.Header.Get("Idempotency-Key"), input)
	if errors.Is(err, coach.ErrNotFound) {
		s.problem(w, r, 404, "RESOURCE_NOT_FOUND", "Resource not found")
		return
	}
	if errors.Is(err, coach.ErrInvalidTransition) {
		s.problem(w, r, 409, "INVALID_TRANSITION", "Recommendation was already decided")
		return
	}
	if errors.Is(err, coach.ErrIdempotencyConflict) {
		s.problem(w, r, 409, "IDEMPOTENCY_CONFLICT", "Idempotency key was already used")
		return
	}
	if err != nil {
		s.problem(w, r, 503, "GROWTH_COACH_UNAVAILABLE", "Growth coach unavailable")
		return
	}
	s.writeJSON(w, 200, map[string]any{"decision": input.Decision, "action": action})
}

func (s *Server) transitionGrowthCoachAction(w http.ResponseWriter, r *http.Request) {
	if !requireMutationKey(s, w, r) {
		return
	}
	var input coach.TransitionInput
	if decodeStrictJSON(w, r, &input) != nil {
		s.problem(w, r, 422, "VALIDATION_FAILED", "Invalid action transition")
		return
	}
	session := sessionFrom(r.Context())
	action, err := s.coach.Transition(r.Context(), session.MerchantID, session.UserID, r.PathValue("id"), r.Header.Get("Idempotency-Key"), input)
	if errors.Is(err, coach.ErrNotFound) {
		s.problem(w, r, 404, "RESOURCE_NOT_FOUND", "Resource not found")
		return
	}
	if errors.Is(err, coach.ErrInvalidTransition) {
		s.problem(w, r, 409, "INVALID_TRANSITION", "This transition is not allowed")
		return
	}
	if errors.Is(err, coach.ErrIdempotencyConflict) {
		s.problem(w, r, 409, "IDEMPOTENCY_CONFLICT", "Idempotency key was already used")
		return
	}
	if err != nil {
		s.problem(w, r, 503, "GROWTH_COACH_UNAVAILABLE", "Growth coach unavailable")
		return
	}
	s.writeJSON(w, 200, action)
}

func (s *Server) decideGrowthCoachDifficulty(w http.ResponseWriter, r *http.Request) {
	if !requireMutationKey(s, w, r) {
		return
	}
	var input coach.DecisionInput
	if decodeStrictJSON(w, r, &input) != nil {
		s.problem(w, r, 422, "VALIDATION_FAILED", "Invalid difficulty decision")
		return
	}
	session := sessionFrom(r.Context())
	proposal, err := s.coach.DecideDifficulty(r.Context(), session.MerchantID, session.UserID, r.PathValue("id"), r.Header.Get("Idempotency-Key"), input)
	if errors.Is(err, coach.ErrNotFound) {
		s.problem(w, r, 404, "RESOURCE_NOT_FOUND", "Resource not found")
		return
	}
	if errors.Is(err, coach.ErrInvalidTransition) {
		s.problem(w, r, 409, "INVALID_TRANSITION", "Difficulty proposal was already decided")
		return
	}
	if errors.Is(err, coach.ErrIdempotencyConflict) {
		s.problem(w, r, 409, "IDEMPOTENCY_CONFLICT", "Idempotency key was already used")
		return
	}
	if err != nil {
		s.problem(w, r, 503, "GROWTH_COACH_UNAVAILABLE", "Growth coach unavailable")
		return
	}
	s.writeJSON(w, 200, proposal)
}

func (s *Server) growthCoachJob(w http.ResponseWriter, r *http.Request) {
	if s.coach == nil {
		s.problem(w, r, 404, "RESOURCE_NOT_FOUND", "Resource not found")
		return
	}
	job, err := s.coach.GetJob(r.Context(), sessionFrom(r.Context()).MerchantID, r.PathValue("jobId"))
	if errors.Is(err, coach.ErrNotFound) {
		s.problem(w, r, 404, "RESOURCE_NOT_FOUND", "Resource not found")
		return
	}
	if err != nil {
		s.problem(w, r, 503, "GROWTH_COACH_UNAVAILABLE", "Growth coach unavailable")
		return
	}
	s.writeJSON(w, 200, job)
}

func (s *Server) growthCoachEvents(w http.ResponseWriter, r *http.Request) {
	if s.coach == nil {
		s.problem(w, r, 404, "RESOURCE_NOT_FOUND", "Resource not found")
		return
	}
	flusher, ok := w.(http.Flusher)
	if !ok {
		s.problem(w, r, 500, "INTERNAL_ERROR", "Streaming unavailable")
		return
	}
	merchantID := sessionFrom(r.Context()).MerchantID
	jobID := r.PathValue("jobId")
	if _, err := s.coach.GetJob(r.Context(), merchantID, jobID); errors.Is(err, coach.ErrNotFound) {
		s.problem(w, r, 404, "RESOURCE_NOT_FOUND", "Resource not found")
		return
	} else if err != nil {
		s.problem(w, r, 503, "GROWTH_COACH_UNAVAILABLE", "Growth coach unavailable")
		return
	}
	w.Header().Set("Content-Type", "text/event-stream; charset=utf-8")
	w.Header().Set("Cache-Control", "no-cache, no-transform")
	w.Header().Set("X-Accel-Buffering", "no")
	poll, heartbeat := time.NewTicker(2*time.Second), time.NewTicker(15*time.Second)
	defer poll.Stop()
	defer heartbeat.Stop()
	last, _ := strconv.ParseInt(r.Header.Get("Last-Event-ID"), 10, 64)
	for {
		events, err := s.coach.EventsAfter(r.Context(), merchantID, jobID, last)
		if err != nil {
			return
		}
		for _, event := range events {
			payload, _ := json.Marshal(event)
			_, _ = fmt.Fprintf(w, "id: %d\nevent: %s\ndata: %s\n\n", event.ID, event.Type, payload)
			last = event.ID
			flusher.Flush()
		}
		job, err := s.coach.GetJob(r.Context(), merchantID, jobID)
		if err != nil {
			return
		}
		if job.State == "COMPLETED" || job.State == "FAILED" {
			return
		}
		select {
		case <-r.Context().Done():
			return
		case <-poll.C:
		case <-heartbeat.C:
			_, _ = fmt.Fprint(w, ": heartbeat\n\n")
			flusher.Flush()
		}
	}
}

func onlyTerminalQuery(r *http.Request) (string, bool) {
	for key := range r.URL.Query() {
		if key != "terminalId" {
			return "", false
		}
	}
	value := r.URL.Query().Get("terminalId")
	return value, len(value) <= 128
}
func requireMutationKey(s *Server, w http.ResponseWriter, r *http.Request) bool {
	if s.coach == nil {
		s.problem(w, r, 404, "RESOURCE_NOT_FOUND", "Resource not found")
		return false
	}
	if !validIdempotencyKey(strings.TrimSpace(r.Header.Get("Idempotency-Key"))) {
		s.problem(w, r, 422, "VALIDATION_FAILED", "A valid Idempotency-Key is required")
		return false
	}
	return true
}