// Package matrix is the multi-corpus retrieval layer above vectord.
// Per docs/SPEC.md §3.4: the matrix indexer composes N single-corpus
// vectord indexes into one retrieve+merge surface, with corpus
// attribution preserved per result. Future work in the same package:
// relevance filter, strong-model downgrade gate, learning-loop
// integration. This file is component 2 of the dependency-ordered
// port plan — multi-corpus retrieve+merge, no filter yet.
//
// Why corpus-as-shard rather than hash-shard a single index:
// different corpora have distinct topology and distinct retrieval
// intent (workers vs candidates vs scrum_findings vs lakehouse_arch).
// Multi-corpus search merges across them by distance — that IS the
// matrix indexer's whole purpose. See feedback_meta_index_vision.md
// and project_small_model_pipeline_vision.md.
package matrix

import (
	"bytes"
	"context"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"log/slog"
	"net/http"
	"sort"
	"sync"
	"time"

	"git.agentview.dev/profit/golangLAKEHOUSE/internal/vectord"
)

// Result is one merged hit with corpus attribution. The corpus field
// is load-bearing — losing it would defeat the matrix's purpose
// (knowing WHICH corpus contributed each hit is half the signal).
type Result struct {
	ID       string          `json:"id"`
	Distance float32         `json:"distance"`
	Corpus   string          `json:"corpus"`
	Metadata json.RawMessage `json:"metadata,omitempty"`
}

// SearchRequest is the matrix search input. Either QueryText (matrix
// embeds it via embedd) or QueryVector (already embedded by caller)
// must be set; QueryVector takes precedence if both supplied.
//
// Playbook fields (component 5 — learning loop):
//   UsePlaybook=true: after normal retrieve+merge, fetch top similar
//     past queries from PlaybookCorpus and apply distance boost to
//     any current results that match a recorded answer.
//   PlaybookCorpus: index name; empty = DefaultPlaybookCorpus.
//   PlaybookTopK: number of similar past queries to consider; 0 =
//     DefaultPlaybookTopK.
//   PlaybookMaxDistance: cosine ceiling for "similar enough" on the
//     BOOST path (re-rank in place); 0 = DefaultPlaybookMaxDistance.
//   PlaybookMaxInjectDistance: tighter cosine ceiling for the SHAPE B
//     INJECT path; 0 = DefaultPlaybookMaxInjectDistance. Splitting the
//     two thresholds is intentional — boost is safe at loose thresholds
//     because it only re-ranks results that already retrieved on their
//     own merits, while inject forces results in and so cross-pollinates
//     wrong-domain answers if the threshold is too loose.
//
// Metadata filter (post-retrieval structured gate):
//   MetadataFilter: map of metadata-field → expected value. Results
//     whose metadata doesn't match every key are dropped. Addresses
//     the reality-test gap surfaced in the candidates/workers
//     experiments — pure semantic retrieval can't gate by status,
//     state, etc. Caller can compensate for filter shrinkage by
//     requesting larger PerCorpusK.
//   Each filter value can be a single value (string|number|bool —
//     whatever JSON unmarshals to `any`) or a []any meaning "any
//     of these values" (OR semantics within one key, AND across keys).
type SearchRequest struct {
	QueryText           string         `json:"query_text,omitempty"`
	QueryVector         []float32      `json:"query_vector,omitempty"`
	Corpora             []string       `json:"corpora"`
	K                   int            `json:"k"`
	PerCorpusK          int            `json:"per_corpus_k,omitempty"`
	Model               string         `json:"model,omitempty"`
	UsePlaybook         bool           `json:"use_playbook,omitempty"`
	PlaybookCorpus      string         `json:"playbook_corpus,omitempty"`
	PlaybookTopK        int            `json:"playbook_top_k,omitempty"`
	PlaybookMaxDistance       float64        `json:"playbook_max_distance,omitempty"`
	PlaybookMaxInjectDistance float64        `json:"playbook_max_inject_distance,omitempty"`
	// JudgeURL: when set, every Shape B injection candidate is
	// rated by an LLM at this Ollama-shape /api/chat endpoint
	// (chatd's /v1/chat works too). Candidates with rating <
	// JudgeMinRating are skipped. Empty = no judge gate (current
	// behavior — distance-only filter).
	JudgeURL       string `json:"judge_url,omitempty"`
	JudgeModel     string `json:"judge_model,omitempty"`
	JudgeMinRating int    `json:"judge_min_rating,omitempty"`
	// QueryRole is an optional role hint that gates Shape A boost +
	// Shape B inject on role match (real_001 cross-role bleed fix).
	// When set, a recorded playbook entry only fires for queries with
	// the same role under roleEqual's normalization. Empty here OR
	// empty on the recorded entry = gate disabled (preserves behavior
	// for callers that don't supply role — e.g. lift-suite multi-
	// constraint queries that have no clean single role).
	QueryRole      string `json:"query_role,omitempty"`
	MetadataFilter map[string]any `json:"metadata_filter,omitempty"`
	// ExcludeIDs filters out specific worker IDs post-retrieval.
	// Real-world driver: a coordinator places 200 workers at a
	// contract, then mid-day the client asks for a different set —
	// the next query should NOT return the already-placed workers.
	// Filter runs after merge but before metadata filter, so an
	// excluded ID never wastes a slot in the post-filter top-K.
	// Also applies to playbook boost + Shape B inject — excluded
	// answers are skipped at injection time.
	ExcludeIDs []string `json:"exclude_ids,omitempty"`
}

// SearchResponse wraps the merged results plus per-corpus return
// counts so callers can detect "this corpus returned nothing"
// without re-querying. PlaybookBoosted is the count of results that
// received a boost from playbook memory; useful for telemetry on
// "how much the learning loop influenced this query."
// MetadataFilterDropped is the count of results dropped by the
// post-retrieval structured filter (when set in the request).
type SearchResponse struct {
	Results               []Result       `json:"results"`
	PerCorpusCounts       map[string]int `json:"per_corpus_counts"`
	PlaybookBoosted       int            `json:"playbook_boosted,omitempty"`
	// PlaybookInjected is Shape B's per-query metric: synthetic
	// results inserted from playbook hits whose answer wasn't already
	// in the regular retrieval. Distinct from PlaybookBoosted (which
	// counts in-place re-ranks of results that WERE present).
	PlaybookInjected      int            `json:"playbook_injected,omitempty"`
	MetadataFilterDropped int            `json:"metadata_filter_dropped,omitempty"`
}

// Retriever holds the HTTP clients to embedd and vectord. Stateless
// otherwise — safe to share across goroutines.
type Retriever struct {
	httpClient *http.Client
	embeddURL  string
	vectordURL string
}

// New returns a Retriever configured to call embedd at embeddURL
// and vectord at vectordURL (both gateway-internal upstreams,
// usually 127.0.0.1:3216 and :3215 respectively).
func New(embeddURL, vectordURL string) *Retriever {
	return &Retriever{
		httpClient: &http.Client{Timeout: 30 * time.Second},
		embeddURL:  embeddURL,
		vectordURL: vectordURL,
	}
}

// Errors surfaced to HTTP handlers.
var (
	ErrEmptyCorpora    = errors.New("matrix: corpora must be non-empty")
	ErrEmptyQuery      = errors.New("matrix: query_text or query_vector required")
	ErrCorpus          = errors.New("matrix: corpus search failed") // wraps vectord errors
	ErrEmbed           = errors.New("matrix: embed failed")
	ErrCorpusNotFound  = errors.New("matrix: corpus not found")     // distinct sentinel for vectord 404
)

// Search runs the matrix retrieve+merge.
//
// Error policy: fail-loud on any corpus error. Silent partial results
// would lie about what was actually searched, which defeats the
// indexer's coverage guarantee. Callers that want best-effort can
// catch the error and re-issue with a smaller corpora list.
func (r *Retriever) Search(ctx context.Context, req SearchRequest) (*SearchResponse, error) {
	if len(req.Corpora) == 0 {
		return nil, ErrEmptyCorpora
	}
	if req.K <= 0 {
		return nil, errors.New("matrix: k must be > 0")
	}
	if req.PerCorpusK <= 0 {
		req.PerCorpusK = req.K
	}

	// Resolve query → vector.
	qvec := req.QueryVector
	if len(qvec) == 0 {
		if req.QueryText == "" {
			return nil, ErrEmptyQuery
		}
		v, err := r.embed(ctx, req.QueryText, req.Model)
		if err != nil {
			return nil, fmt.Errorf("%w: %v", ErrEmbed, err)
		}
		qvec = v
	}

	// Parallel search across corpora. Each shard is independent;
	// fan-out + collect with WaitGroup is cleaner than channels-only.
	type shardResult struct {
		corpus string
		hits   []vectord.Result
		err    error
	}
	results := make([]shardResult, len(req.Corpora))
	var wg sync.WaitGroup
	for i, c := range req.Corpora {
		wg.Add(1)
		go func(i int, corpus string) {
			defer wg.Done()
			hits, err := r.searchCorpus(ctx, corpus, qvec, req.PerCorpusK)
			results[i] = shardResult{corpus: corpus, hits: hits, err: err}
		}(i, c)
	}
	wg.Wait()

	var allHits []Result
	perCorpus := make(map[string]int, len(req.Corpora))
	for _, s := range results {
		if s.err != nil {
			return nil, fmt.Errorf("%w: %s: %v", ErrCorpus, s.corpus, s.err)
		}
		perCorpus[s.corpus] = len(s.hits)
		for _, h := range s.hits {
			allHits = append(allHits, Result{
				ID: h.ID, Distance: h.Distance, Corpus: s.corpus, Metadata: h.Metadata,
			})
		}
	}

	// Stable sort so equal-distance ties keep input order (which is
	// per-corpus order from vectord's HNSW result heap). This matters
	// for deterministic test assertions.
	sort.SliceStable(allHits, func(i, j int) bool {
		return allHits[i].Distance < allHits[j].Distance
	})

	// ExcludeIDs filter — applied first so excluded IDs don't waste
	// a slot in the post-filter top-K. Real-world driver: coordinator
	// has placed N workers at a contract; mid-day the client asks for
	// alternatives, so this query passes ExcludeIDs=<placed_ids> and
	// gets back fresh candidates instead of the same N.
	if len(req.ExcludeIDs) > 0 {
		excludeSet := make(map[string]bool, len(req.ExcludeIDs))
		for _, id := range req.ExcludeIDs {
			excludeSet[id] = true
		}
		kept := make([]Result, 0, len(allHits))
		for _, h := range allHits {
			if !excludeSet[h.ID] {
				kept = append(kept, h)
			}
		}
		allHits = kept
	}

	// Metadata filter (component B — staffing-side structured gate).
	// Applied BEFORE top-K truncation so the filter doesn't accidentally
	// reduce coverage further. Caller can request larger PerCorpusK to
	// compensate when filters are aggressive.
	var dropped int
	if len(req.MetadataFilter) > 0 {
		filtered := make([]Result, 0, len(allHits))
		for _, h := range allHits {
			if matchesMetadataFilter(h.Metadata, req.MetadataFilter) {
				filtered = append(filtered, h)
			} else {
				dropped++
			}
		}
		allHits = filtered
	}

	if len(allHits) > req.K {
		allHits = allHits[:req.K]
	}
	resp := &SearchResponse{
		Results:               allHits,
		PerCorpusCounts:       perCorpus,
		MetadataFilterDropped: dropped,
	}

	// Playbook (component 5) — both boost (re-rank existing) and
	// inject (Shape B: bring in answers that aren't in regular
	// retrieval). Reuses the query vector — no extra embed call.
	// Missing playbook corpus is a legitimate cold-start no-op.
	if req.UsePlaybook {
		hits, err := r.fetchPlaybookHits(ctx, qvec, req)
		if err != nil {
			slog.Warn("matrix: playbook lookup failed; skipping boost+inject", "err", err)
		} else if len(hits) > 0 {
			// Filter playbook hits to honor ExcludeIDs — without this,
			// an excluded answer in a playbook recording would re-enter
			// the result set via Shape B inject, defeating the swap
			// semantics that the exclude list exists to enforce.
			if len(req.ExcludeIDs) > 0 {
				excludeSet := make(map[string]bool, len(req.ExcludeIDs))
				for _, id := range req.ExcludeIDs {
					excludeSet[id] = true
				}
				keptHits := make([]PlaybookHit, 0, len(hits))
				for _, h := range hits {
					if !excludeSet[h.Entry.AnswerID] {
						keptHits = append(keptHits, h)
					}
				}
				hits = keptHits
			}
			resp.PlaybookBoosted = ApplyPlaybookBoost(req.QueryRole, resp.Results, hits)
			maxInjectDist := float32(req.PlaybookMaxInjectDistance)
			if maxInjectDist <= 0 {
				maxInjectDist = float32(DefaultPlaybookMaxInjectDistance)
			}
			// Optional LLM judge gate (per OPEN item #1). nil when
			// JudgeURL/JudgeModel are unset → distance-only filter.
			var gate InjectGate
			if g := NewLLMJudgeGate(req.JudgeURL, req.JudgeModel, req.JudgeMinRating, nil); g != nil {
				gate = g
			}
			var injected int
			resp.Results, injected = InjectPlaybookMisses(req.QueryText, req.QueryRole, resp.Results, hits, maxInjectDist, gate)
			resp.PlaybookInjected = injected
			if injected > 0 {
				// Re-sort + truncate after injection. ApplyPlaybookBoost
				// already sorted, but injection appends past the end —
				// resort to merge, then enforce K.
				sort.SliceStable(resp.Results, func(i, j int) bool {
					return resp.Results[i].Distance < resp.Results[j].Distance
				})
				if len(resp.Results) > req.K {
					resp.Results = resp.Results[:req.K]
				}
			}
		}
	}

	return resp, nil
}

// fetchPlaybookHits queries the playbook corpus with the same query
// vector and returns hits whose decoded entries are within
// PlaybookMaxDistance. A missing playbook corpus returns nil + nil
// (legitimate no-op state for a system before any Record call).
func (r *Retriever) fetchPlaybookHits(ctx context.Context, qvec []float32, req SearchRequest) ([]PlaybookHit, error) {
	corpus := req.PlaybookCorpus
	if corpus == "" {
		corpus = DefaultPlaybookCorpus
	}
	topK := req.PlaybookTopK
	if topK <= 0 {
		topK = DefaultPlaybookTopK
	}
	maxDist := req.PlaybookMaxDistance
	if maxDist <= 0 {
		maxDist = DefaultPlaybookMaxDistance
	}

	rawHits, err := r.searchCorpus(ctx, corpus, qvec, topK)
	if errors.Is(err, ErrCorpusNotFound) {
		// Cold-start state: no Record call has happened yet, so the
		// playbook corpus doesn't exist. Legit no-op, not an error.
		return nil, nil
	}
	if err != nil {
		return nil, err
	}

	out := make([]PlaybookHit, 0, len(rawHits))
	for _, h := range rawHits {
		if float64(h.Distance) > maxDist {
			continue
		}
		entry, err := UnmarshalPlaybookMetadata(h.Metadata)
		if err != nil {
			slog.Warn("matrix: skip malformed playbook entry", "id", h.ID, "err", err)
			continue
		}
		out = append(out, PlaybookHit{
			PlaybookID: h.ID,
			Distance:   h.Distance,
			Entry:      entry,
		})
	}
	return out, nil
}

// Record stores a (query → answer_id) playbook entry in the
// playbook corpus. Embeds the query via embedd, ensures the corpus
// exists (idempotent create), and writes the entry as one vectord
// item with the entry's JSON in metadata.
//
// Uses a deterministic ID derived from (query_text, answer_id,
// answer_corpus) so re-recording the same triple upserts (last
// score wins). Callers wanting to accumulate distinct samples can
// vary one of the three.
//
// corpus="" defaults to DefaultPlaybookCorpus.
func (r *Retriever) Record(ctx context.Context, entry PlaybookEntry, corpus string) (string, error) {
	if err := entry.Validate(); err != nil {
		return "", err
	}
	if corpus == "" {
		corpus = DefaultPlaybookCorpus
	}

	qvec, err := r.embed(ctx, entry.QueryText, "")
	if err != nil {
		return "", fmt.Errorf("playbook record embed: %w", err)
	}

	if err := r.ensureCorpus(ctx, corpus, len(qvec)); err != nil {
		return "", fmt.Errorf("playbook ensure corpus: %w", err)
	}

	if entry.RecordedAtNs == 0 {
		entry.RecordedAtNs = time.Now().UnixNano()
	}

	pbID := playbookID(entry.QueryText, entry.AnswerID, entry.AnswerCorpus)

	meta, err := entry.MarshalMetadata()
	if err != nil {
		return "", err
	}

	if err := r.addItem(ctx, corpus, pbID, qvec, meta); err != nil {
		return "", fmt.Errorf("playbook add: %w", err)
	}
	return pbID, nil
}

// playbookID is sha256-truncated 8 bytes (16 hex chars) prefixed
// with "pb-". Deterministic on (query, answer_id, answer_corpus).
func playbookID(query, answerID, answerCorpus string) string {
	h := sha256.Sum256([]byte(query + "|" + answerID + "|" + answerCorpus))
	return "pb-" + hex.EncodeToString(h[:8])
}

// ensureCorpus creates a vectord index if it doesn't exist.
// 201 = created; 409 = already exists; both fine for idempotent use.
func (r *Retriever) ensureCorpus(ctx context.Context, name string, dim int) error {
	body, err := json.Marshal(map[string]any{
		"name": name, "dimension": dim, "distance": "cosine",
	})
	if err != nil {
		return err
	}
	httpReq, err := http.NewRequestWithContext(ctx, http.MethodPost,
		r.vectordURL+"/vectors/index", bytes.NewReader(body))
	if err != nil {
		return err
	}
	httpReq.Header.Set("Content-Type", "application/json")
	resp, err := r.httpClient.Do(httpReq)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	io.Copy(io.Discard, resp.Body)
	if resp.StatusCode == http.StatusCreated || resp.StatusCode == http.StatusConflict {
		return nil
	}
	return fmt.Errorf("ensure %q: status %d", name, resp.StatusCode)
}

// addItem POSTs a single-item batch to /vectors/index/{name}/add.
func (r *Retriever) addItem(ctx context.Context, corpus, id string, vec []float32, meta json.RawMessage) error {
	body, err := json.Marshal(map[string]any{
		"items": []map[string]any{
			{"id": id, "vector": vec, "metadata": meta},
		},
	})
	if err != nil {
		return err
	}
	url := r.vectordURL + "/vectors/index/" + corpus + "/add"
	httpReq, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(body))
	if err != nil {
		return err
	}
	httpReq.Header.Set("Content-Type", "application/json")
	resp, err := r.httpClient.Do(httpReq)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		b, _ := io.ReadAll(resp.Body)
		return fmt.Errorf("add %q: status %d: %s", corpus, resp.StatusCode, b)
	}
	return nil
}

// matchesMetadataFilter reports whether a result's metadata satisfies
// the filter. Each filter key must be present in the metadata; the
// value must equal (or for a list filter, contain) the metadata
// value. Missing key = drop. Type mismatches are JSON-equality
// checked (e.g. filter wants 1 but metadata has 1.0 → match via
// canonical JSON form).
//
// Filter value semantics:
//   string|number|bool → exact equality (after JSON normalization)
//   []any              → OR within key (any element matching wins)
//
// AND across keys: every filter key must match.
func matchesMetadataFilter(rawMeta json.RawMessage, filter map[string]any) bool {
	if len(filter) == 0 {
		return true
	}
	if len(rawMeta) == 0 {
		return false // no metadata can't satisfy any filter
	}
	var meta map[string]any
	if err := json.Unmarshal(rawMeta, &meta); err != nil {
		return false
	}
	for k, expected := range filter {
		got, present := meta[k]
		if !present {
			return false
		}
		if !valueMatches(got, expected) {
			return false
		}
	}
	return true
}

// valueMatches handles single-value and list-value filter semantics.
// JSON-canonical equality so 1 ≡ 1.0 and "true" != true.
func valueMatches(got, expected any) bool {
	if list, ok := expected.([]any); ok {
		for _, e := range list {
			if jsonEqual(got, e) {
				return true
			}
		}
		return false
	}
	return jsonEqual(got, expected)
}

// jsonEqual marshals both sides and compares the canonical forms.
// Handles the float64-vs-int problem inherent to encoding/json
// (which decodes all numbers as float64) — both sides go through
// the same encoder so 1 == 1.0 if both came in as numbers.
func jsonEqual(a, b any) bool {
	ab, errA := json.Marshal(a)
	bb, errB := json.Marshal(b)
	if errA != nil || errB != nil {
		return false
	}
	return string(ab) == string(bb)
}

// Corpora returns the list of vectord index names. Thin proxy to
// GET /vectors/index — exposed at the matrix layer so callers don't
// need direct vectord access.
func (r *Retriever) Corpora(ctx context.Context) ([]string, error) {
	url := r.vectordURL + "/vectors/index"
	httpReq, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
	if err != nil {
		return nil, err
	}
	resp, err := r.httpClient.Do(httpReq)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		b, _ := io.ReadAll(resp.Body)
		return nil, fmt.Errorf("vectord index list: status %d: %s", resp.StatusCode, b)
	}
	var out struct {
		Names []string `json:"names"`
	}
	if err := json.NewDecoder(resp.Body).Decode(&out); err != nil {
		return nil, err
	}
	return out.Names, nil
}

// embed POSTs a single-text /embed call. Reuses embedd's batched
// /embed shape with len(texts)==1; embedd's LRU cache absorbs
// repeat queries (commit 56844c3).
func (r *Retriever) embed(ctx context.Context, text, model string) ([]float32, error) {
	body, err := json.Marshal(map[string]any{"texts": []string{text}, "model": model})
	if err != nil {
		return nil, err
	}
	httpReq, err := http.NewRequestWithContext(ctx, http.MethodPost, r.embeddURL+"/embed", bytes.NewReader(body))
	if err != nil {
		return nil, err
	}
	httpReq.Header.Set("Content-Type", "application/json")
	resp, err := r.httpClient.Do(httpReq)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		b, _ := io.ReadAll(resp.Body)
		return nil, fmt.Errorf("embed status %d: %s", resp.StatusCode, b)
	}
	var out struct {
		Vectors [][]float32 `json:"vectors"`
	}
	if err := json.NewDecoder(resp.Body).Decode(&out); err != nil {
		return nil, err
	}
	if len(out.Vectors) == 0 {
		return nil, errors.New("embed returned no vectors")
	}
	return out.Vectors[0], nil
}

// searchCorpus calls vectord /vectors/index/{name}/search. Returns
// ErrCorpusNotFound (wrapped) on HTTP 404 so callers can distinguish
// "this corpus doesn't exist" from "this corpus errored." Per
// 2026-04-29 cross-lineage scrum (Opus + Kimi convergent): caught
// the original strings.Contains "status 404" detection that would
// silently break if the error format changed.
func (r *Retriever) searchCorpus(ctx context.Context, corpus string, vec []float32, k int) ([]vectord.Result, error) {
	body, err := json.Marshal(map[string]any{"vector": vec, "k": k})
	if err != nil {
		return nil, err
	}
	url := r.vectordURL + "/vectors/index/" + corpus + "/search"
	httpReq, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(body))
	if err != nil {
		return nil, err
	}
	httpReq.Header.Set("Content-Type", "application/json")
	resp, err := r.httpClient.Do(httpReq)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()
	if resp.StatusCode == http.StatusNotFound {
		return nil, fmt.Errorf("%w: %s", ErrCorpusNotFound, corpus)
	}
	if resp.StatusCode != http.StatusOK {
		b, _ := io.ReadAll(resp.Body)
		return nil, fmt.Errorf("status %d: %s", resp.StatusCode, b)
	}
	var out struct {
		Results []vectord.Result `json:"results"`
	}
	if err := json.NewDecoder(resp.Body).Decode(&out); err != nil {
		return nil, err
	}
	return out.Results, nil
}