package summarizer

import (
	"context"
	"io"
	"net/http"
	"regexp"
	"strings"
	"time"

	openai "github.com/sashabaranov/go-openai"

	"sojuboy/internal/config"
	"sojuboy/internal/store"
)

type OpenAI struct {
	apiKey    string
	baseURL   string
	model     string
	maxTokens int
	// runtime cfg
	followLinks  bool
	linkTimeout  time.Duration
	linkMaxBytes int
	groupWindow  time.Duration
	maxLinks     int
}

func NewOpenAI(apiKey, baseURL, model string, maxTokens int) *OpenAI {
	return &OpenAI{apiKey: apiKey, baseURL: baseURL, model: model, maxTokens: maxTokens,
		followLinks: true, linkTimeout: 6 * time.Second, linkMaxBytes: 262144, groupWindow: 90 * time.Second, maxLinks: 5,
	}
}

// Configure from app config
func (o *OpenAI) ApplyConfig(cfg config.Config) {
	o.followLinks = cfg.SummFollowLinks
	o.linkTimeout = cfg.SummLinkTimeout
	o.linkMaxBytes = cfg.SummLinkMaxBytes
	o.groupWindow = cfg.SummGroupWindow
	o.maxLinks = cfg.SummMaxLinks
}

func (o *OpenAI) Summarize(ctx context.Context, channel string, msgs []store.Message, window time.Duration) (string, error) {
	if o == nil || o.apiKey == "" {
		return "", nil
	}
	cfg := openai.DefaultConfig(o.apiKey)
	if strings.TrimSpace(o.baseURL) != "" {
		cfg.BaseURL = o.baseURL
	}
	client := openai.NewClientWithConfig(cfg)

	// 1) Group multiline posts from same author within groupWindow
	grouped := groupMessages(msgs, o.groupWindow)

	// 2) Extract links and optionally fetch a small amount of content
	links := extractLinks(grouped)
	if o.followLinks && len(links) > 0 {
		links = fetchLinkSnippets(ctx, links, o.linkTimeout, o.linkMaxBytes, o.maxLinks)
	}

	// 3) Build a concise, natural prompt
	var b strings.Builder
	b.WriteString("Channel: ")
	b.WriteString(channel)
	b.WriteString("\nTime window: ")
	b.WriteString(window.String())
	b.WriteString("\n\nTranscript (grouped by author):\n")
	for _, g := range grouped {
		b.WriteString(g.time.Format(time.RFC3339))
		b.WriteString(" ")
		b.WriteString(g.author)
		b.WriteString(": ")
		b.WriteString(g.text)
		b.WriteString("\n")
	}
	if len(links) > 0 {
		b.WriteString("\nReferenced content (snippets):\n")
		for _, ln := range links {
			b.WriteString("- ")
			b.WriteString(ln.url)
			b.WriteString(" → ")
			b.WriteString(ln.snippet)
			b.WriteString("\n")
		}
	}
	b.WriteString("\nWrite a concise, readable summary of the conversation above.\n")
	b.WriteString("- Focus on what happened and why it matters.\n")
	b.WriteString("- Integrate linked content and pasted multi-line posts naturally.\n")
	b.WriteString("- Avoid rigid sections; use short paragraphs or light bullets if helpful.\n")
	b.WriteString("- Keep it compact but don’t omit important context.\n")
	prompt := b.String()

	sys := "You summarize IRC transcripts. Be concise, natural, and informative."

	model := o.model
	if strings.TrimSpace(model) == "" {
		model = "gpt-4o-mini"
	}
	reasoningLike := strings.HasPrefix(model, "gpt-5") || strings.HasPrefix(model, "o1") || strings.Contains(model, "reasoning")

	req := openai.ChatCompletionRequest{
		Model: model,
		Messages: []openai.ChatCompletionMessage{
			{Role: openai.ChatMessageRoleSystem, Content: sys},
			{Role: openai.ChatMessageRoleUser, Content: prompt},
		},
		MaxCompletionTokens: o.maxTokens,
	}
	if !reasoningLike {
		req.Temperature = 0.3
	}

	resp, err := client.CreateChatCompletion(ctx, req)
	if err != nil {
		return "", err
	}
	if len(resp.Choices) == 0 {
		return "", nil
	}
	return strings.TrimSpace(resp.Choices[0].Message.Content), nil
}

type linkSnippet struct {
	url     string
	snippet string
}

type groupedMsg struct {
	time   time.Time
	author string
	text   string
}

func groupMessages(msgs []store.Message, window time.Duration) []groupedMsg {
	if len(msgs) == 0 {
		return nil
	}
	var out []groupedMsg
	cur := groupedMsg{time: msgs[0].Time, author: msgs[0].Author, text: msgs[0].Body}
	for i := 1; i < len(msgs); i++ {
		m := msgs[i]
		if m.Author == cur.author && m.Time.Sub(cur.time) <= window {
			cur.text += "\n" + m.Body
			continue
		}
		out = append(out, cur)
		cur = groupedMsg{time: m.Time, author: m.Author, text: m.Body}
	}
	out = append(out, cur)
	return out
}

var linkRe = regexp.MustCompile(`https?://\S+`)

func extractLinks(msgs []groupedMsg) []linkSnippet {
	var links []linkSnippet
	for _, g := range msgs {
		for _, m := range linkRe.FindAllString(g.text, -1) {
			links = append(links, linkSnippet{url: m})
		}
	}
	return links
}

func fetchLinkSnippets(ctx context.Context, links []linkSnippet, timeout time.Duration, maxBytes int, maxLinks int) []linkSnippet {
	client := &http.Client{Timeout: timeout}
	if len(links) > maxLinks {
		links = links[:maxLinks]
	}
	out := make([]linkSnippet, 0, len(links))
	for _, ln := range links {
		req, err := http.NewRequestWithContext(ctx, http.MethodGet, ln.url, nil)
		if err != nil {
			continue
		}
		resp, err := client.Do(req)
		if err != nil {
			continue
		}
		func() {
			defer resp.Body.Close()
			if resp.StatusCode < 200 || resp.StatusCode >= 300 {
				return
			}
			limited := io.LimitedReader{R: resp.Body, N: int64(maxBytes)}
			b, err := io.ReadAll(&limited)
			if err != nil || len(b) == 0 {
				return
			}
			// naive text cleanup
			text := string(b)
			text = strings.ReplaceAll(text, "\r", "")
			text = strings.TrimSpace(text)
			if len(text) > 800 {
				text = text[:800]
			}
			out = append(out, linkSnippet{url: ln.url, snippet: text})
		}()
	}
	return out
}