package scheduling

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

// HTTPSchedulingPolicy implements SchedulingPolicy by calling the scheduling service over HTTP.
type HTTPSchedulingPolicy struct {
	baseURL string
	client  *http.Client
}

// NewHTTPSchedulingPolicy creates a client against the scheduling HTTP endpoint (e.g. "http://scheduling:8080").
func NewHTTPSchedulingPolicy(baseURL string, client *http.Client) *HTTPSchedulingPolicy {
	if client == nil {
		client = &http.Client{Timeout: 5 * time.Second}
	}
	return &HTTPSchedulingPolicy{
		baseURL: strings.TrimRight(baseURL, "/"),
		client:  client,
	}
}

func (c *HTTPSchedulingPolicy) GetAvailability(ctx context.Context, resourceID string, from, to time.Time, durationMinutes int) ([]Slot, error) {
	u := fmt.Sprintf("%s/api/scheduling/resources/%s/availability?from=%s&to=%s",
		c.baseURL,
		url.PathEscape(resourceID),
		url.QueryEscape(from.Format(time.RFC3339)),
		url.QueryEscape(to.Format(time.RFC3339)),
	)
	if durationMinutes > 0 {
		u += "&duration=" + strconv.Itoa(durationMinutes)
	}

	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u, nil)
	if err != nil {
		return nil, err
	}
	req.Header.Set("Accept", "application/json")

	resp, err := c.client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("scheduling client: GetAvailability failed: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode == http.StatusNotFound {
		return nil, ErrResourceNotFound
	}
	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return nil, fmt.Errorf("scheduling client: unexpected status %d: %s", resp.StatusCode, string(body))
	}

	var slots []Slot
	if err := json.NewDecoder(resp.Body).Decode(&slots); err != nil {
		return nil, fmt.Errorf("scheduling client: decode slots: %w", err)
	}
	return slots, nil
}

func (c *HTTPSchedulingPolicy) HoldSlot(ctx context.Context, reqData HoldRequest) (HoldResult, error) {
	data, err := json.Marshal(reqData)
	if err != nil {
		return HoldResult{}, err
	}

	u := fmt.Sprintf("%s/api/scheduling/holds", c.baseURL)
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, u, bytes.NewReader(data))
	if err != nil {
		return HoldResult{}, err
	}
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Accept", "application/json")

	resp, err := c.client.Do(req)
	if err != nil {
		return HoldResult{}, fmt.Errorf("scheduling client: HoldSlot failed: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode == http.StatusConflict {
		return HoldResult{}, ErrSlotUnavailable
	}
	if resp.StatusCode != http.StatusCreated && resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return HoldResult{}, fmt.Errorf("scheduling client: HoldSlot status %d: %s", resp.StatusCode, string(body))
	}

	var res HoldResult
	if err := json.NewDecoder(resp.Body).Decode(&res); err != nil {
		return HoldResult{}, fmt.Errorf("scheduling client: decode hold result: %w", err)
	}
	return res, nil
}

func (c *HTTPSchedulingPolicy) ReleaseHold(ctx context.Context, holdID string) error {
	u := fmt.Sprintf("%s/api/scheduling/holds/%s/release", c.baseURL, url.PathEscape(holdID))
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, u, nil)
	if err != nil {
		return err
	}

	resp, err := c.client.Do(req)
	if err != nil {
		return fmt.Errorf("scheduling client: ReleaseHold failed: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusNoContent && resp.StatusCode != http.StatusNotFound {
		body, _ := io.ReadAll(resp.Body)
		return fmt.Errorf("scheduling client: ReleaseHold status %d: %s", resp.StatusCode, string(body))
	}
	return nil
}

func (c *HTTPSchedulingPolicy) ExtendHold(ctx context.Context, holdID string, extensionSeconds int) (HoldResult, error) {
	payload := map[string]int{"extension_seconds": extensionSeconds}
	data, _ := json.Marshal(payload)

	u := fmt.Sprintf("%s/api/scheduling/holds/%s/extend", c.baseURL, url.PathEscape(holdID))
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, u, bytes.NewReader(data))
	if err != nil {
		return HoldResult{}, err
	}
	req.Header.Set("Content-Type", "application/json")

	resp, err := c.client.Do(req)
	if err != nil {
		return HoldResult{}, fmt.Errorf("scheduling client: ExtendHold failed: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode == http.StatusNotFound || resp.StatusCode == http.StatusGone {
		return HoldResult{}, ErrHoldExpired
	}
	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return HoldResult{}, fmt.Errorf("scheduling client: ExtendHold status %d: %s", resp.StatusCode, string(body))
	}

	var res HoldResult
	if err := json.NewDecoder(resp.Body).Decode(&res); err != nil {
		return HoldResult{}, fmt.Errorf("scheduling client: decode extend result: %w", err)
	}
	return res, nil
}

func (c *HTTPSchedulingPolicy) ConfirmBooking(ctx context.Context, holdID, orderID, customerEmail, customerName, notes string) (BookingDetails, error) {
	payload := map[string]string{
		"hold_id":        holdID,
		"order_id":       orderID,
		"customer_email": customerEmail,
		"customer_name":  customerName,
		"notes":          notes,
	}
	data, _ := json.Marshal(payload)

	u := fmt.Sprintf("%s/api/scheduling/bookings", c.baseURL)
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, u, bytes.NewReader(data))
	if err != nil {
		return BookingDetails{}, err
	}
	req.Header.Set("Content-Type", "application/json")

	resp, err := c.client.Do(req)
	if err != nil {
		return BookingDetails{}, fmt.Errorf("scheduling client: ConfirmBooking failed: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode == http.StatusGone || resp.StatusCode == http.StatusConflict {
		return BookingDetails{}, ErrHoldExpired
	}
	if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusCreated {
		body, _ := io.ReadAll(resp.Body)
		return BookingDetails{}, fmt.Errorf("scheduling client: ConfirmBooking status %d: %s", resp.StatusCode, string(body))
	}

	var details BookingDetails
	if err := json.NewDecoder(resp.Body).Decode(&details); err != nil {
		return BookingDetails{}, fmt.Errorf("scheduling client: decode booking details: %w", err)
	}
	return details, nil
}

func (c *HTTPSchedulingPolicy) CancelBooking(ctx context.Context, bookingID, reason string) error {
	payload := map[string]string{"reason": reason}
	data, _ := json.Marshal(payload)

	u := fmt.Sprintf("%s/api/scheduling/bookings/%s/cancel", c.baseURL, url.PathEscape(bookingID))
	req, err := http.NewRequestWithContext(ctx, http.MethodPatch, u, bytes.NewReader(data))
	if err != nil {
		return err
	}
	req.Header.Set("Content-Type", "application/json")

	resp, err := c.client.Do(req)
	if err != nil {
		return fmt.Errorf("scheduling client: CancelBooking failed: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode == http.StatusNotFound {
		return ErrBookingNotFound
	}
	if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusNoContent {
		body, _ := io.ReadAll(resp.Body)
		return fmt.Errorf("scheduling client: CancelBooking status %d: %s", resp.StatusCode, string(body))
	}
	return nil
}