package cpmstar

import (
	"encoding/json"
	"fmt"
	"net/http"

	"github.com/prebid/openrtb/v20/openrtb2"
	"github.com/prebid/prebid-server/v4/adapters"
	"github.com/prebid/prebid-server/v4/config"
	"github.com/prebid/prebid-server/v4/errortypes"
	"github.com/prebid/prebid-server/v4/openrtb_ext"
	"github.com/prebid/prebid-server/v4/util/jsonutil"
)

type Adapter struct {
	endpoint string
}

func (a *Adapter) MakeRequests(request *openrtb2.BidRequest, unused *adapters.ExtraRequestInfo) ([]*adapters.RequestData, []error) {
	var errs []error
	var adapterRequests []*adapters.RequestData

	if err := preprocess(request); err != nil {
		errs = append(errs, err)
		return nil, errs
	}

	adapterReq, err := a.makeRequest(request)
	if err != nil {
		errs = append(errs, err)
		return nil, errs
	}

	adapterRequests = append(adapterRequests, adapterReq)

	return adapterRequests, errs
}

func (a *Adapter) makeRequest(request *openrtb2.BidRequest) (*adapters.RequestData, error) {
	var err error

	jsonBody, err := json.Marshal(request)
	if err != nil {
		return nil, err
	}

	headers := http.Header{}
	headers.Add("Content-Type", "application/json;charset=utf-8")

	return &adapters.RequestData{
		Method:  "POST",
		Uri:     a.endpoint,
		Body:    jsonBody,
		Headers: headers,
		ImpIDs:  openrtb_ext.GetImpIDs(request.Imp),
	}, nil
}

func preprocess(request *openrtb2.BidRequest) error {
	if len(request.Imp) == 0 {
		return &errortypes.BadInput{
			Message: "No Imps in Bid Request",
		}
	}

	// Process each impression in the bid request
	//
	// FIELD HANDLING BEHAVIOR:
	// - PRESERVES: All non-bidder fields (gpid, prebid, schain, custom fields, etc.)
	// - TRANSFORMS: Extracts bidder config from nested structure and flattens to root level
	// - EXPLICITLY REMOVES: Only the 'bidder' wrapper key (contents are preserved but flattened)
	//
	// Example transformation:
	// Input:  {"gpid": "/path", "bidder": {"placementId": 123}, "custom": "value"}
	// Output: {"gpid": "/path", "placementId": 123, "custom": "value"}
	for i := range request.Imp {
		var imp = &request.Imp[i]

		// Parse the original extension into a generic map to preserve all fields
		var originalExt map[string]json.RawMessage
		if err := jsonutil.Unmarshal(imp.Ext, &originalExt); err != nil {
			return &errortypes.BadInput{
				Message: err.Error(),
			}
		}

		// Extract the "bidder" field from the already parsed extension
		bidderRaw, exists := originalExt["bidder"]
		if !exists {
			return &errortypes.BadInput{
				Message: "bidder field not found in impression extension",
			}
		}

		if err := validateImp(imp); err != nil {
			return err
		}

		// Create new extension object that preserves all original fields except 'bidder'
		newExt := make(map[string]json.RawMessage)
		for key, value := range originalExt {
			if key != "bidder" {
				newExt[key] = value
			}
		}

		// Add bidder configuration fields directly to the root level
		var bidderConfig map[string]interface{}
		if err := jsonutil.Unmarshal(bidderRaw, &bidderConfig); err != nil {
			return &errortypes.BadInput{
				Message: err.Error(),
			}
		}

		for key, value := range bidderConfig {
			valueBytes, err := json.Marshal(value)
			if err != nil {
				return &errortypes.BadInput{
					Message: err.Error(),
				}
			}
			newExt[key] = valueBytes
		}

		// Marshal the new extension object
		modifiedExt, err := json.Marshal(newExt)
		if err != nil {
			return &errortypes.BadInput{
				Message: err.Error(),
			}
		}
		imp.Ext = modifiedExt
	}

	return nil
}

func validateImp(imp *openrtb2.Imp) error {
	if imp.Banner == nil && imp.Video == nil {
		return &errortypes.BadInput{
			Message: "Only Banner and Video bid-types are supported at this time",
		}
	}
	return nil
}

// MakeBids based on cpmstar server response
func (a *Adapter) MakeBids(bidRequest *openrtb2.BidRequest, unused *adapters.RequestData, responseData *adapters.ResponseData) (*adapters.BidderResponse, []error) {
	if responseData.StatusCode == http.StatusNoContent {
		return nil, nil
	}

	if responseData.StatusCode != http.StatusOK {
		return nil, []error{&errortypes.BadServerResponse{
			Message: fmt.Sprintf("Unexpected HTTP status code: %d. Run with request.debug = 1 for more info", responseData.StatusCode),
		}}
	}

	var bidResponse openrtb2.BidResponse

	if err := jsonutil.Unmarshal(responseData.Body, &bidResponse); err != nil {
		return nil, []error{&errortypes.BadServerResponse{
			Message: err.Error(),
		}}
	}

	if len(bidResponse.SeatBid) == 0 {
		return nil, nil
	}

	rv := adapters.NewBidderResponseWithBidsCapacity(len(bidResponse.SeatBid[0].Bid))
	var errors []error

	for _, seatbid := range bidResponse.SeatBid {
		for i := range seatbid.Bid {
			foundMatchingBid := false
			bidType := openrtb_ext.BidTypeBanner
			for _, imp := range bidRequest.Imp {
				if imp.ID == seatbid.Bid[i].ImpID {
					foundMatchingBid = true
					if imp.Banner != nil {
						bidType = openrtb_ext.BidTypeBanner
					} else if imp.Video != nil {
						bidType = openrtb_ext.BidTypeVideo
					}
					break
				}
			}

			if foundMatchingBid {
				rv.Bids = append(rv.Bids, &adapters.TypedBid{
					Bid:     &seatbid.Bid[i],
					BidType: bidType,
				})
			} else {
				errors = append(errors, &errortypes.BadServerResponse{
					Message: fmt.Sprintf("bid id='%s' could not find valid impid='%s'", seatbid.Bid[i].ID, seatbid.Bid[i].ImpID),
				})
			}
		}
	}
	return rv, errors
}

// Builder builds a new instance of the Cpmstar adapter for the given bidder with the given config.
func Builder(bidderName openrtb_ext.BidderName, config config.Adapter, server config.Server) (adapters.Bidder, error) {
	bidder := &Adapter{
		endpoint: config.Endpoint,
	}
	return bidder, nil
}