package api

import (
	"context"
	"errors"
	"fmt"
	"time"
	"unicode/utf8"

	"git.wntrmute.dev/kyle/sift/internal/auth"
	"git.wntrmute.dev/kyle/sift/internal/batch"
	"git.wntrmute.dev/kyle/sift/internal/clean"
	"git.wntrmute.dev/kyle/sift/internal/digest"
	"git.wntrmute.dev/kyle/sift/internal/fetch"
	"git.wntrmute.dev/kyle/sift/internal/fleetctx"
	"git.wntrmute.dev/kyle/sift/internal/pdfdoc"
	"git.wntrmute.dev/kyle/sift/internal/recover"
)

// fetchTarget runs one target's per-target pipeline: fetch → recover → PDF render or clean →
// question limit → digest → context → log line → envelope. It is the single body both /v1/fetch
// and the batch worker drive, so it must not change what v1fetch returned.
func (s *Server) fetchTarget(ctx context.Context, c *auth.Caller, t batch.Target) (batch.Result, error) {
	q := t.Options.Question
	if len([]rune(q)) > 500 {
		rns := []rune(q)
		q = string(rns[:500])
	}
	mode := t.Options.Mode
	if mode == "" {
		if q != "" {
			mode = "digest"
		} else {
			mode = "clean"
		}
	}
	if mode != "clean" && mode != "raw" && mode != "digest" {
		return batch.Result{}, &fetch.Error{Status: 400, Msg: "invalid url"}
	}
	wantCtx := q != ""
	if t.Options.Context != nil {
		wantCtx = *t.Options.Context
	}

	t0 := time.Now()
	onlyMain := true
	res, cl, doc, ferr := s.doFetch(ctx, c, t.URL, t.Options.JQ, onlyMain)
	var snap *recover.Result
	if ferr != nil && t.Options.Recover && recoverWorthy(ferr) {
		sr, rerr := recover.Try(ctx, s.Fetch, t.URL)
		if rerr == nil && sr != nil && sr.Res != nil {
			res, cl, doc, ferr = s.cleanFetched(sr.Res, t.Options.JQ, onlyMain)
			snap = sr
		}
	}
	if ferr != nil {
		return batch.Result{}, ferr
	}
	fetchMS := time.Since(t0).Milliseconds()

	if doc == nil && (t.Options.Pages != "" || t.Options.Grep != "") {
		return batch.Result{}, &fetch.Error{Status: 400, Msg: "pages and grep apply to PDFs only"}
	}

	var docLen, pdfPages int
	var content string
	var pdfMap map[string]any
	if doc != nil {
		pdfPages = doc.Pages
		if mode == "raw" {
			return batch.Result{}, &fetch.Error{Status: 400, Msg: "raw mode does not apply to PDFs"}
		}
		rp, err := s.renderPDF(doc, pdfdoc.Options{Pages: t.Options.Pages, Grep: t.Options.Grep, OutCap: s.OutCap})
		if err != nil {
			if errors.Is(err, pdfdoc.ErrBadPages) || errors.Is(err, pdfdoc.ErrBadGrep) {
				return batch.Result{}, &fetch.Error{Status: 400, Msg: err.Error()}
			}
			return batch.Result{}, err
		}
		full := pdfdoc.Full(doc)
		docLen = utf8.RuneCountInString(full)
		if mode == "digest" {
			content = full
		} else {
			content = rp.Content
		}
		pdfMap = map[string]any{
			"pages":     doc.Pages,
			"title":     doc.Title,
			"outline":   doc.Outline,
			"extracted": len(doc.Text),
			"first":     rp.First,
			"last":      rp.Last,
			"map":       rp.Map,
			"grep_hits": rp.GrepHits,
			"note":      rp.Note,
		}
	} else {
		content = cl.Markdown
		if cl.Kind == "json" {
			content = cl.HTML
		}
		if mode == "raw" {
			content = string(res.Body)
			if len(content) > s.OutCap {
				content = clean.TruncateUTF8(content, s.OutCap)
				cl.Trunc = true
				cl.Warning = "truncated to output cap"
			}
		}
	}
	warn := []string{}
	if cl.Warning != "" {
		warn = append(warn, cl.Warning)
	}

	var digMeta map[string]any
	var digestMS int64
	if mode == "digest" {
		if doc != nil {
			n := len(digest.Split(pdfdoc.Full(doc), digest.ChunkTokens))
			limit := s.PDFMaxQuestionChunks
			if limit == 0 {
				limit = DefaultPDFMaxQuestionChunks
			}
			if n > limit {
				return batch.Result{}, &fetch.Error{Status: 422, Msg: fmt.Sprintf("document too long for question (%d chunks); use grep or pages", n)}
			}
		}
		if s.Digest == nil {
			warn = append(warn, "digest fell back to clean: unset")
			mode = "clean"
			content, warn = capDigestFallback(content, warn)
			digMeta = map[string]any{"fallback": "unset"}
		} else {
			dr := s.Digest.Run(ctx, content, q, res.FinalURL, s.callerClass(c))
			digestMS = dr.DigestMS
			if !dr.Cached {
				s.Prom.ObserveDigest(time.Duration(dr.DigestMS) * time.Millisecond)
			}
			if dr.Fallback != "" {
				warn = append(warn, "digest fell back to clean: "+dr.Fallback)
				mode = "clean"
				content, warn = capDigestFallback(content, warn)
				digMeta = map[string]any{"fallback": dr.Fallback, "model": dr.Model}
			} else {
				content = dr.Text
				digMeta = map[string]any{
					"model":        dr.Model,
					"chunks_used":  dr.ChunksUsed,
					"chunks_total": dr.ChunksTotal,
					"retrieval":    dr.Retrieval,
					"embedded":     dr.Embedded,
					"fallback":     false,
					"cached":       dr.Cached,
				}
			}
		}
	}

	var ctxItems []fleetctx.Item
	var ctxMS int64
	if wantCtx && s.Ctx != nil {
		ct0 := time.Now()
		query := fleetctx.Query(q, cl.Title, headings(cl.Markdown))
		items, cw := s.Ctx.Search(ctx, c.Workspace, c.Name, query)
		ctxMS = time.Since(ct0).Milliseconds()
		if cw != "" {
			warn = append(warn, cw)
		}
		ctxItems = items
	}

	qLen := len(q)
	if qLen > 80 {
		qLen = 80
	}
	fb, _ := "", false
	if digMeta != nil {
		if s, ok := digMeta["fallback"].(string); ok {
			fb = s
		}
	}
	s.Log.Info("fetch", "caller", c.Name, "host", s.logHost(c, res.FinalURL), "mode", mode,
		"q_len", qLen, "raw_tokens", len(res.Body)/4, "returned_tokens", len(content)/4,
		"pdf_pages", pdfPages, "digest_ms", digestMS, "fallback", fb)

	src := map[string]any{
		"url":          res.URL,
		"final_url":    res.FinalURL,
		"status":       res.Status,
		"content_type": res.ContentType,
		"fetched_at":   res.FetchedAt.Format(time.RFC3339),
		"hash":         res.SHA256(),
		"bytes":        len(res.Body),
		"cached":       len(res.Body) == 0,
		"kind":         "live",
	}
	if snap != nil {
		src["kind"] = "snapshot"
		src["via"] = string(snap.Via)
		src["original_url"] = snap.OriginalURL
		if snap.SnapshotAt != "" {
			src["snapshot_at"] = snap.SnapshotAt
		} else {
			src["snapshot_at"] = nil
			warn = append(warn, "snapshot date unknown")
		}
	}
	m := map[string]any{
		"mode":      mode,
		"untrusted": true,
		"source":    src,
		"warnings":  warn,
		"sizes": map[string]int{
			"raw_tokens":      docLen / 4,
			"clean_tokens":    digest.EstTokens(cl.Markdown),
			"returned_tokens": digest.EstTokens(content),
		},
		"timings": map[string]int64{"fetch_ms": fetchMS, "digest_ms": digestMS, "context_ms": ctxMS},
	}
	if pdfMap != nil {
		m["pdf"] = pdfMap
	}
	if digMeta != nil {
		m["digest"] = digMeta
	}
	if wantCtx {
		m["context"] = ctxItems
	}
	return batch.Result{Content: content, Meta: m}, nil
}