package fetchers

import (
	"encoding/json"
	"fmt"
	"io"
	"llostre/backend/general"
	"log/slog"
	"net"
	"net/http"
	"strings"
)

type DIDDocument struct {
	AlsoKnownAs []string `json:"alsoKnownAs"`
	Service     []struct {
		ID              string `json:"id"`
		Type            string `json:"type"`
		ServiceEndpoint string `json:"serviceEndpoint"`
	} `json:"service"`
}

func FetchDID(handle string) (string, error) {
	// return if it's a DID already
	if strings.HasPrefix(handle, "did:") {
		return handle, nil
	}

	// resolve DNS record first
	txtRecords, err := net.LookupTXT("_atproto." + handle)
	if err == nil {
		for _, txt := range txtRecords {
			if after, ok := strings.CutPrefix(txt, "did="); ok {
				return after, nil
			}
		}
	}

	// fallback to HTTPS well-known
	resp, err := http.Get(fmt.Sprintf("https://%s/.well-known/atproto-did", handle))
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return "", err
	}

	did := strings.TrimSpace(string(body))
	if !strings.HasPrefix(did, "did:") {
		return "", fmt.Errorf("invalid DID returned: %s", did)
	}

	return did, nil
}

func FetchDidDoc(did string) (*DIDDocument, error) {
	didDocURL := fmt.Sprintf("https://plc.directory/%s", did)

	resp, err := http.Get(didDocURL)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	if resp.StatusCode != 200 {
		return nil, fmt.Errorf("DID resolution failed: %d", resp.StatusCode)
	}

	var didDoc DIDDocument
	if err := json.NewDecoder(resp.Body).Decode(&didDoc); err != nil {
		return nil, err
	}

	return &didDoc, nil
}

func FetchHandle(did string) (string, error) {
	var didDoc, err = FetchDidDoc(did)
	if err != nil {
		return "", err
	}

	if len(didDoc.AlsoKnownAs) == 0 {
		return "", fmt.Errorf("no handle found")
	}

	handle := strings.TrimPrefix(didDoc.AlsoKnownAs[0], "at://")
	return handle, nil
}

func FetchPDS(did string) (string, error) {
	var didDoc, err = FetchDidDoc(did)
	if err != nil {
		return "", err
	}

	for _, svc := range didDoc.Service {
		if svc.Type == "AtprotoPersonalDataServer" {
			return svc.ServiceEndpoint, nil
		}
	}

	return "", fmt.Errorf("no PDS found for DID %s", did)
}

func FetchHandleAndPDS(did string) (string, string, error) {
	var didDoc, err = FetchDidDoc(did)
	if err != nil {
		return "", "", err
	}

	if len(didDoc.AlsoKnownAs) == 0 {
		return "", "", fmt.Errorf("no handle found")
	}

	var pds string
	for _, svc := range didDoc.Service {
		if svc.Type == "AtprotoPersonalDataServer" {
			pds = svc.ServiceEndpoint
			break
		}
	}

	handle := strings.TrimPrefix(didDoc.AlsoKnownAs[0], "at://")

	return handle, pds, nil
}

func FetchProfile(logger *slog.Logger, did, pdsURL, slingshotURL string, cache *Cache) (*general.Profile, error) {
	// construct profile record URI
	uri := fmt.Sprintf("at://%s/app.bsky.actor.profile/self", did)

	// try slingshot first
	if slingshotURL != "" {
		rawRecord, err := general.FetchRawRecordByURI(logger, uri, slingshotURL)
		if err != nil {
			logger.Warn("slingshot profile fetch failed", "did", did, "error", err)
		} else {
			return parseProfile(did, rawRecord, cache)
		}
	}

	// fallback to PDS
	rawRecord, err := general.FetchRawRecordByURI(logger, uri, pdsURL)
	if err != nil {
		return nil, err
	}

	return parseProfile(did, rawRecord, cache)
}

func FetchProfiles(logger *slog.Logger, dids []string, pdsURL, slingshotURL string, cache *Cache) map[string]general.Profile {
	profiles := make(map[string]general.Profile)
	for _, did := range dids {
		profile, err := FetchProfile(logger, did, pdsURL, slingshotURL, cache)
		if err == nil {
			profiles[did] = *profile
		}
	}
	return profiles
}

func parseProfile(did string, rawRecord *general.RawRecord, cache *Cache) (*general.Profile, error) {
	var profileData general.ProfileRecord
	if err := json.Unmarshal(rawRecord.Value, &profileData); err != nil {
		return nil, err
	}

	var avatarURL, bannerURL string
	if profileData.Avatar != nil {
		avatarURL = fmt.Sprintf("https://cdn.bsky.app/img/avatar/plain/%s/%s@jpeg", did, profileData.Avatar.Ref.Link)
	}
	if profileData.Banner != nil {
		bannerURL = fmt.Sprintf("https://cdn.bsky.app/img/banner/plain/%s/%s@jpeg", did, profileData.Banner.Ref.Link)
	}

	handle, err := FetchHandle(did)
	if err != nil {
		handle = "handle.invalid"
	}

	profile := &general.Profile{
		Handle:      handle,
		DisplayName: profileData.DisplayName,
		AvatarURL:   avatarURL,
		BannerURL:   bannerURL,
		Pronouns:    profileData.Pronouns,
	}

	cache.SetProfile(did, profile)
	return profile, nil
}