package main

import (
	"bytes"
	"crypto/sha256"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"regexp"
	"strings"
	"time"
)

// Publisher handles posting items to AT Protocol PDS
type Publisher struct {
	pdsHost    string
	httpClient *http.Client
}

// PDSSession holds authentication info for a PDS account
type PDSSession struct {
	DID        string `json:"did"`
	Handle     string `json:"handle"`
	AccessJwt  string `json:"accessJwt"`
	RefreshJwt string `json:"refreshJwt"`
}

// BskyPost represents an app.bsky.feed.post record
type BskyPost struct {
	Type      string      `json:"$type"`
	Text      string      `json:"text"`
	CreatedAt string      `json:"createdAt"`
	Facets    []BskyFacet `json:"facets,omitempty"`
	Embed     *BskyEmbed  `json:"embed,omitempty"`
}

type BskyFacet struct {
	Index    BskyByteSlice `json:"index"`
	Features []BskyFeature `json:"features"`
}

type BskyByteSlice struct {
	ByteStart int `json:"byteStart"`
	ByteEnd   int `json:"byteEnd"`
}

type BskyFeature struct {
	Type string `json:"$type"`
	URI  string `json:"uri,omitempty"`
	Tag  string `json:"tag,omitempty"` // For hashtag facets
}

type BskyEmbed struct {
	Type     string        `json:"$type"`
	External *BskyExternal `json:"external,omitempty"`
	Images   []BskyImage   `json:"images,omitempty"`
}

type BskyExternal struct {
	URI         string   `json:"uri"`
	Title       string   `json:"title"`
	Description string   `json:"description"`
	Thumb       *BlobRef `json:"thumb,omitempty"`
}

type BskyImage struct {
	Alt         string           `json:"alt"`
	Image       *BlobRef         `json:"image"`
	AspectRatio *BskyAspectRatio `json:"aspectRatio,omitempty"`
}

type BskyAspectRatio struct {
	Width  int `json:"width"`
	Height int `json:"height"`
}

// NewPublisher creates a new Publisher instance
func NewPublisher(pdsHost string) *Publisher {
	return &Publisher{
		pdsHost: pdsHost,
		httpClient: &http.Client{
			Timeout: 30 * time.Second,
		},
	}
}

// TID alphabet for base32-sortable encoding
const tidAlphabet = "234567abcdefghijklmnopqrstuvwxyz"

// GenerateRkey creates a deterministic TID-format rkey from a GUID and timestamp
// TIDs are required by Bluesky relay for indexing - custom rkeys don't sync
// Format: 13 chars base32-sortable, 53 bits timestamp + 10 bits clock ID
func GenerateRkey(guid string, timestamp time.Time) string {
	if guid == "" {
		return ""
	}

	// Get microseconds since Unix epoch (53 bits)
	microsInt := timestamp.UnixMicro()
	if microsInt < 0 {
		microsInt = 0
	}
	// Convert to uint64 and mask to 53 bits
	micros := uint64(microsInt) & ((1 << 53) - 1)

	// Generate deterministic 10-bit clock ID from GUID hash
	// Use XOR of multiple hash bytes to reduce collisions
	hash := sha256.Sum256([]byte(guid))
	// XOR bytes 0-3 together, then 4-7, combine for more entropy
	h1 := uint64(hash[0]) ^ uint64(hash[2]) ^ uint64(hash[4]) ^ uint64(hash[6])
	h2 := uint64(hash[1]) ^ uint64(hash[3]) ^ uint64(hash[5]) ^ uint64(hash[7])
	clockID := (h1 << 2) | (h2 >> 6)
	clockID = clockID & ((1 << 10) - 1) // 10 bits = 0-1023

	// Combine: top bit 0, 53 bits timestamp, 10 bits clock ID
	tid := (micros << 10) | clockID

	// Encode as base32-sortable (13 characters)
	var result [13]byte
	for i := 12; i >= 0; i-- {
		result[i] = tidAlphabet[tid&0x1f]
		tid >>= 5
	}

	return string(result[:])
}

// extractURLs finds all URLs in a string
func extractURLs(text string) []string {
	// Match http:// or https:// URLs
	urlRegex := regexp.MustCompile(`https?://[^\s<>"'\)]+`)
	matches := urlRegex.FindAllString(text, -1)

	// Clean up trailing punctuation
	var urls []string
	for _, u := range matches {
		// Remove trailing punctuation that's likely not part of the URL
		u = strings.TrimRight(u, ".,;:!?")
		if u != "" {
			urls = append(urls, u)
		}
	}
	return urls
}

// toCamelCaseTag converts a tag string to camelCase hashtag format
// e.g., "Lagos News" -> "lagosNews", "AI" -> "ai", "machine learning" -> "machineLearning"
func toCamelCaseTag(tag string) string {
	tag = strings.TrimSpace(tag)
	if tag == "" {
		return ""
	}

	// Remove any # prefix if present
	tag = strings.TrimPrefix(tag, "#")

	// Split on spaces and other separators
	words := strings.FieldsFunc(tag, func(r rune) bool {
		return r == ' ' || r == '-' || r == '_'
	})

	if len(words) == 0 {
		return ""
	}

	// If single word, return lowercased
	if len(words) == 1 {
		return strings.ToLower(words[0])
	}

	// Multiple words: lowercase first word, capitalize first letter of subsequent words
	var result strings.Builder
	for i, word := range words {
		if word == "" {
			continue
		}
		runes := []rune(word)
		if len(runes) > 0 {
			if i == 0 || result.Len() == 0 {
				// First word: all lowercase
				result.WriteString(strings.ToLower(word))
			} else {
				// Subsequent words: capitalize first letter, lowercase rest
				result.WriteString(strings.ToUpper(string(runes[0])))
				if len(runes) > 1 {
					result.WriteString(strings.ToLower(string(runes[1:])))
				}
			}
		}
	}
	return result.String()
}

// formatTagsForPost converts item tags to hashtag text and facets
// Returns the hashtag line (e.g., "#AI #MachineLearning #News") and facets
func formatTagsForPost(tags []string, textOffset int) (string, []BskyFacet) {
	if len(tags) == 0 {
		return "", nil
	}

	// Dedupe and convert tags
	seen := make(map[string]bool)
	var hashtags []string
	for _, tag := range tags {
		camel := toCamelCaseTag(tag)
		if camel == "" || seen[strings.ToLower(camel)] {
			continue
		}
		seen[strings.ToLower(camel)] = true
		hashtags = append(hashtags, camel)
	}

	if len(hashtags) == 0 {
		return "", nil
	}

	// Limit to 5 tags to keep post compact
	if len(hashtags) > 5 {
		hashtags = hashtags[:5]
	}

	// Build the hashtag line and facets
	var line strings.Builder
	var facets []BskyFacet
	currentOffset := textOffset

	for i, ht := range hashtags {
		if i > 0 {
			line.WriteString(" ")
			currentOffset++
		}

		hashtagText := "#" + ht
		byteStart := currentOffset
		byteEnd := currentOffset + len(hashtagText)

		line.WriteString(hashtagText)

		facets = append(facets, BskyFacet{
			Index: BskyByteSlice{
				ByteStart: byteStart,
				ByteEnd:   byteEnd,
			},
			Features: []BskyFeature{{
				Type: "app.bsky.richtext.facet#tag",
				Tag:  ht,
			}},
		})

		currentOffset = byteEnd
	}

	return line.String(), facets
}

// PublishItem posts a feed item to the PDS
// Returns the AT URI of the created record, or error
func (p *Publisher) PublishItem(session *PDSSession, item *Item) (string, error) {
	if item.GUID == "" && item.Link == "" {
		return "", fmt.Errorf("item has no GUID or link, cannot publish")
	}

	// Collect URLs: main link + HN comments link (if applicable)
	// Limit to 2 URLs max to stay under 300 grapheme limit
	urlSet := make(map[string]bool)
	var allURLs []string

	// Add main link first
	if item.Link != "" {
		urlSet[item.Link] = true
		allURLs = append(allURLs, item.Link)
	}

	// For HN feeds, add comments link from description (looks like "https://news.ycombinator.com/item?id=...")
	descURLs := extractURLs(item.Description)
	for _, u := range descURLs {
		if strings.Contains(u, "news.ycombinator.com/item") && !urlSet[u] {
			urlSet[u] = true
			allURLs = append(allURLs, u)
			break // Only add one comments link
		}
	}

	// Add enclosure URL for podcasts/media (audio/video) if we have room
	// Bluesky has 300 char limit, so only add if total URLs + minimal title fits
	if len(allURLs) < 2 && item.Enclosure != nil && item.Enclosure.URL != "" {
		encType := strings.ToLower(item.Enclosure.Type)
		if strings.HasPrefix(encType, "audio/") || strings.HasPrefix(encType, "video/") {
			if !urlSet[item.Enclosure.URL] {
				// Calculate if enclosure would fit (need ~60 chars for title + separators)
				currentURLLen := 0
				for _, u := range allURLs {
					currentURLLen += len(u) + 2 // +2 for \n\n
				}
				enclosureLen := len(item.Enclosure.URL) + 2
				if currentURLLen+enclosureLen < 235 { // Leave 60 chars for title
					urlSet[item.Enclosure.URL] = true
					allURLs = append(allURLs, item.Enclosure.URL)
				}
			}
		}
	}

	// Get the primary URL (article link)
	primaryURL := ""
	if len(allURLs) > 0 {
		primaryURL = allURLs[0]
	}

	// Use original publication date if available, otherwise current time
	createdAt := time.Now()
	if !item.PubDate.IsZero() {
		createdAt = item.PubDate
	}

	// Build post text with hashtags if available
	// The link card shows the title, description, and thumbnail
	// Clicking the card doesn't trigger the "leaving Bluesky" warning
	postText := ""
	var facets []BskyFacet

	if len(item.Tags) > 0 {
		tagLine, tagFacets := formatTagsForPost(item.Tags, 0)
		postText = tagLine
		facets = tagFacets
	}

	post := BskyPost{
		Type:      "app.bsky.feed.post",
		Text:      postText,
		CreatedAt: createdAt.Format(time.RFC3339),
		Facets:    facets,
	}

	// Always use external embed (link card) - clicking the card doesn't show "leaving" warning
	if primaryURL != "" {
		external := &BskyExternal{
			URI:         primaryURL,
			Title:       item.Title,
			Description: truncate(stripHTML(item.Description), 300),
		}

		// Add thumbnail from first image if available
		if len(item.ImageURLs) > 0 {
			if thumb := p.fetchAndUploadImage(session, item.ImageURLs[0]); thumb != nil {
				external.Thumb = thumb
			}
		}

		post.Embed = &BskyEmbed{
			Type:     "app.bsky.embed.external",
			External: external,
		}
	}

	// Use GUID + discoveredAt for deterministic rkey
	// This allows regenerating a new rkey by updating discoveredAt if needed
	guidForRkey := item.GUID
	if guidForRkey == "" {
		guidForRkey = item.Link
	}
	// Use PubDate for rkey to match createdAt ordering, fall back to DiscoveredAt
	rkeyTime := item.PubDate
	if rkeyTime.IsZero() {
		rkeyTime = item.DiscoveredAt
	}
	rkey := GenerateRkey(guidForRkey, rkeyTime)

	// Create the record with deterministic rkey
	payload := map[string]interface{}{
		"repo":       session.DID,
		"collection": "app.bsky.feed.post",
		"rkey":       rkey,
		"record":     post,
	}

	body, err := json.Marshal(payload)
	if err != nil {
		return "", err
	}

	req, err := http.NewRequest("POST", p.pdsHost+"/xrpc/com.atproto.repo.createRecord", bytes.NewReader(body))
	if err != nil {
		return "", err
	}
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Authorization", "Bearer "+session.AccessJwt)

	resp, err := p.httpClient.Do(req)
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()

	respBody, _ := io.ReadAll(resp.Body)

	if resp.StatusCode != http.StatusOK {
		return "", fmt.Errorf("create record failed: %s - %s", resp.Status, string(respBody))
	}

	var result struct {
		URI string `json:"uri"`
		CID string `json:"cid"`
	}
	if err := json.Unmarshal(respBody, &result); err != nil {
		return "", err
	}

	return result.URI, nil
}

func truncate(s string, maxLen int) string {
	if len(s) <= maxLen {
		return s
	}
	return s[:maxLen-3] + "..."
}

// stripHTML removes HTML tags from a string
func stripHTML(s string) string {
	// Remove HTML tags
	tagRegex := regexp.MustCompile(`<[^>]*>`)
	s = tagRegex.ReplaceAllString(s, "")

	// Decode common HTML entities
	s = strings.ReplaceAll(s, "&amp;", "&")
	s = strings.ReplaceAll(s, "&lt;", "<")
	s = strings.ReplaceAll(s, "&gt;", ">")
	s = strings.ReplaceAll(s, "&quot;", "\"")
	s = strings.ReplaceAll(s, "&#39;", "'")
	s = strings.ReplaceAll(s, "&nbsp;", " ")

	// Collapse whitespace
	spaceRegex := regexp.MustCompile(`\s+`)
	s = spaceRegex.ReplaceAllString(s, " ")

	return strings.TrimSpace(s)
}