package order

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

	"git.k6n.net/mats/go-cart-actor/pkg/flow"
)

type InventoryReservationLine struct {
	SKU        string `json:"sku"`
	LocationID string `json:"locationId"`
	Quantity   uint32 `json:"quantity"`
}

type InventoryReservationRequest struct {
	HolderID string                     `json:"holderId"`
	TTL      time.Duration              `json:"-"`
	Lines    []InventoryReservationLine `json:"lines"`
}

type InventoryReservationService interface {
	Reserve(ctx context.Context, req InventoryReservationRequest) error
	Release(ctx context.Context, req InventoryReservationRequest) error
}

type HTTPInventoryReservationService struct {
	baseURL string
	client  *http.Client
}

func NewHTTPInventoryReservationService(baseURL string, client *http.Client) (*HTTPInventoryReservationService, error) {
	baseURL = strings.TrimRight(strings.TrimSpace(baseURL), "/")
	if baseURL == "" {
		return nil, fmt.Errorf("inventory reservation service: missing base url")
	}
	if client == nil {
		client = &http.Client{Timeout: 10 * time.Second}
	}
	return &HTTPInventoryReservationService{baseURL: baseURL, client: client}, nil
}

func (s *HTTPInventoryReservationService) Reserve(ctx context.Context, req InventoryReservationRequest) error {
	return s.post(ctx, "/reservations", req)
}

func (s *HTTPInventoryReservationService) Release(ctx context.Context, req InventoryReservationRequest) error {
	return s.post(ctx, "/reservations/release", req)
}

func (s *HTTPInventoryReservationService) post(ctx context.Context, path string, req InventoryReservationRequest) error {
	body := map[string]any{
		"holderId": req.HolderID,
		"lines":    req.Lines,
	}
	if req.TTL > 0 {
		body["ttlSeconds"] = int64(req.TTL / time.Second)
	}
	raw, err := json.Marshal(body)
	if err != nil {
		return err
	}
	httpReq, err := http.NewRequestWithContext(ctx, http.MethodPost, s.baseURL+path, bytes.NewReader(raw))
	if err != nil {
		return err
	}
	httpReq.Header.Set("Content-Type", "application/json")
	resp, err := s.client.Do(httpReq)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	if resp.StatusCode >= 300 {
		return fmt.Errorf("inventory reservation service: %s returned %d", path, resp.StatusCode)
	}
	return nil
}

type reserveInventoryParams struct {
	HolderID   string `json:"holderId,omitempty"`
	TTLSeconds int64  `json:"ttlSeconds,omitempty"`
	Lines      []struct {
		Reference  string `json:"reference"`
		Quantity   int32  `json:"quantity"`
		LocationID string `json:"locationId,omitempty"`
	} `json:"lines"`
}

func RegisterInventoryReservationActions(reg *flow.Registry, app Applier, svc InventoryReservationService) {
	reg.ActionWithMeta("reserve_inventory", func(ctx context.Context, st *flow.State, params json.RawMessage) error {
		if svc == nil {
			return fmt.Errorf("reserve_inventory: no reservation service configured")
		}
		req, err := buildInventoryReservationRequest(ctx, app, st, params, "reserve_inventory")
		if err != nil {
			return err
		}
		return svc.Reserve(ctx, req)
	}, flow.CapabilityMeta{
		Description:   "Reserve inventory for specific order lines through the inventory service.",
		ExampleParams: json.RawMessage(`{"ttlSeconds":900,"lines":[{"reference":"l1","quantity":1,"locationId":"se"}]}`),
	})

	reg.ActionWithMeta("release_inventory", func(ctx context.Context, st *flow.State, params json.RawMessage) error {
		if svc == nil {
			return fmt.Errorf("release_inventory: no reservation service configured")
		}
		req, err := buildInventoryReservationRequest(ctx, app, st, params, "release_inventory")
		if err != nil {
			return err
		}
		return svc.Release(ctx, req)
	}, flow.CapabilityMeta{
		Description:   "Release a prior inventory reservation for specific order lines.",
		ExampleParams: json.RawMessage(`{"lines":[{"reference":"l1","quantity":1,"locationId":"se"}]}`),
	})
}

func buildInventoryReservationRequest(ctx context.Context, app Applier, st *flow.State, params json.RawMessage, action string) (InventoryReservationRequest, error) {
	var p reserveInventoryParams
	if err := json.Unmarshal(params, &p); err != nil {
		return InventoryReservationRequest{}, fmt.Errorf("%s: bad params: %w", action, err)
	}
	if len(p.Lines) == 0 {
		return InventoryReservationRequest{}, fmt.Errorf("%s: missing lines", action)
	}
	o, err := app.Get(ctx, st.ID)
	if err != nil {
		return InventoryReservationRequest{}, err
	}
	holderID := p.HolderID
	if holderID == "" {
		holderID = "order:" + OrderId(st.ID).String()
	}
	req := InventoryReservationRequest{HolderID: holderID}
	if p.TTLSeconds > 0 {
		req.TTL = time.Duration(p.TTLSeconds) * time.Second
	}
	for _, lineReq := range p.Lines {
		if lineReq.Reference == "" {
			return InventoryReservationRequest{}, fmt.Errorf("%s: line missing reference", action)
		}
		if lineReq.Quantity <= 0 {
			return InventoryReservationRequest{}, fmt.Errorf("%s: line %q has invalid quantity %d", action, lineReq.Reference, lineReq.Quantity)
		}
		line := o.findLine(lineReq.Reference)
		if line == nil {
			return InventoryReservationRequest{}, fmt.Errorf("%s: unknown line %q", action, lineReq.Reference)
		}
		if line.Sku == "" {
			return InventoryReservationRequest{}, fmt.Errorf("%s: line %q has no sku", action, lineReq.Reference)
		}
		remaining := line.Quantity - line.Fulfilled
		if int(lineReq.Quantity) > remaining {
			return InventoryReservationRequest{}, fmt.Errorf("%s: line %q quantity %d exceeds remaining fulfillable %d", action, lineReq.Reference, lineReq.Quantity, remaining)
		}
		locationID := strings.TrimSpace(lineReq.LocationID)
		if locationID == "" {
			locationID = strings.TrimSpace(line.Location)
		}
		if locationID == "" {
			locationID = strings.TrimSpace(o.Country)
		}
		if locationID == "" {
			return InventoryReservationRequest{}, fmt.Errorf("%s: line %q has no location", action, lineReq.Reference)
		}
		req.Lines = append(req.Lines, InventoryReservationLine{
			SKU:        line.Sku,
			LocationID: locationID,
			Quantity:   uint32(lineReq.Quantity),
		})
	}
	return req, nil
}