package indexer

import (
	"sync"

	"github.com/zzet/gortex/internal/clones"
	"github.com/zzet/gortex/internal/graph"
)

// incrementalCloneIndex maintains the clone-detection state (CMS +
// length-stratified LSH) live across single-file edits so a (re)index of
// one file updates EdgeSimilarTo edges in O(edited file) instead of the
// whole-graph detectClonesAndEmitEdges recompute. It is the steady-state
// counterpart of the batch pass: the batch pass re-baselines (corrects CMS
// drift) and runs diffusion; this index keeps the direct similar_to edges
// in step between batch passes.
//
// Source of truth in-session is the in-memory shingles cache; the durable
// copy lives in the CloneShingle* sidecar so Rebuild can reseed the CMS
// after a warm restart without re-parsing. Signatures are computed through
// the same kernel the batch pass uses (computeCloneSigFromShingles), so at
// a given corpus the incremental and batch edge sets are identical.
//
// It is NOT goroutine-safe beyond its own mutex — every method takes the
// lock — and is driven under the indexer's write path (one goroutine at a
// time), the same single-writer discipline the underlying clones.CMS /
// clones.StratifiedIndex assume.
type incrementalCloneIndex struct {
	mu       sync.Mutex
	cms      *clones.CMS
	lsh      *clones.StratifiedIndex
	shingles map[string][]uint64 // node id -> raw shingle set (cache)
	corpus   int
	built    bool
}

// newIncrementalCloneIndex returns an empty, un-built index. built stays
// false until a batch pass or Rebuild seeds it from the graph / sidecar;
// while un-built the indexer falls back to the whole-graph clone pass.
func newIncrementalCloneIndex() *incrementalCloneIndex {
	return &incrementalCloneIndex{
		cms:      clones.NewCMS(65536, 4),
		lsh:      clones.NewStratifiedIndex(),
		shingles: make(map[string][]uint64),
	}
}

// tokensFromMeta reads a node's stamped normalised-token count, tolerating
// the int / int64 / float64 shapes a backend round-trip may produce.
// Mirrors the switch in detectClonesAndEmitEdgesCtx so the LSH length
// classes match the batch pass.
func tokensFromMeta(n *graph.Node) int {
	if n == nil || n.Meta == nil {
		return 0
	}
	switch v := n.Meta[cloneTokensMetaKey].(type) {
	case int:
		return v
	case int64:
		return int(v)
	case float64:
		return int(v)
	}
	return 0
}

// cloneFuncNodes filters a node slice to the function/method nodes that
// participate in clone detection.
func cloneFuncNodes(nodes []*graph.Node) []*graph.Node {
	out := make([]*graph.Node, 0, len(nodes))
	for _, n := range nodes {
		if n == nil {
			continue
		}
		if n.Kind == graph.KindFunction || n.Kind == graph.KindMethod {
			out = append(out, n)
		}
	}
	return out
}

// Rebuild resets the index and reseeds it from the graph's current
// signatures plus the persisted shingle sidecar. It is the warmup /
// post-batch / warm-restart path: after the whole-graph clone pass has
// stamped clone_sig on the surviving bodies (and finaliseCloneSignatures
// has persisted clone_shingles for EVERY eligible body — survivors and
// boilerplate-dropped alike — to the sidecar), Rebuild walks this repo's
// bodies, rebuilds the CMS + corpus from the persisted shingles, banks
// each surviving signature into the live LSH index, and marks built=true
// so subsequent edits go incremental.
//
// The CMS and corpus MUST mirror finaliseCloneSignatures' bodies set: that
// pass builds its CMS and useFilter/threshold from ALL eligible bodies
// (every func/method node that had clone_shingles), including the ones it
// then drops as boilerplate-dominated (no clone_sig). Seeding the CMS /
// corpus only from survivors (clone_sig present) would under-count the
// sketch and shrink the corpus, so the incremental path would filter
// against a different threshold than the batch finalise and stamp
// different signatures on the edited file. We therefore seed CMS + corpus
// from every body with persisted shingles and gate ONLY the LSH Add on a
// decodable clone_sig (survivors). This makes Rebuild's CMS/corpus
// byte-match what the batch finalise produced.
//
// Repo-scoped: it walks the repo's nodes (via cloneRepoNodes) filtered to
// n.RepoPrefix == repoPrefix so each per-repo index's corpus counts only that
// repo's bodies — matching its repo-scoped LoadCloneShingles seed. An
// unfiltered walk would count every repo's bodies into a single repo's corpus
// and skew its threshold. cloneRepoNodes uses GetRepoNodes when repoPrefix is
// non-empty (the daemon multi-repo case), so a warm restart no longer decodes
// the whole graph's nodes to rebuild one repo's index; it falls back to
// AllNodes only in single-repo / in-memory mode, where repoPrefix is "" and
// those nodes are not tracked in the byRepo buckets GetRepoNodes reads (so
// GetRepoNodes("") would be empty and the "" == n.RepoPrefix filter matches
// every node instead).
//
// Tolerant of a missing/partial sidecar: a body with a clone_sig but no
// persisted shingle row still enters the LSH index (so its edges are
// maintained) — that body just contributes nothing to the CMS / corpus,
// which at the re-baseline corpus is corrected at the next batch pass.
func (ci *incrementalCloneIndex) Rebuild(g graph.Store, repoPrefix string) {
	if ci == nil || g == nil {
		return
	}
	ci.mu.Lock()
	defer ci.mu.Unlock()

	ci.cms = clones.NewCMS(65536, 4)
	ci.lsh = clones.NewStratifiedIndex()
	ci.shingles = make(map[string][]uint64)
	ci.corpus = 0

	var load map[string][]uint64
	if r, ok := g.(graph.CloneShingleReader); ok {
		if rows, err := r.LoadCloneShingles(repoPrefix); err == nil {
			load = rows
		}
	}

	for _, n := range cloneRepoNodes(g, repoPrefix) {
		if n == nil {
			continue
		}
		if n.RepoPrefix != repoPrefix {
			continue
		}
		if n.Kind != graph.KindFunction && n.Kind != graph.KindMethod {
			continue
		}
		// Seed CMS + corpus from every eligible body that has persisted
		// shingles — survivors AND boilerplate-dropped bodies — so the
		// sketch and corpus mirror finaliseCloneSignatures' bodies set.
		sh := load[n.ID]
		if len(sh) > 0 {
			for _, s := range sh {
				ci.cms.Add(s)
			}
			ci.shingles[n.ID] = sh
			ci.corpus++
		}
		// Only survivors (a decodable clone_sig) enter the LSH index —
		// dropped bodies have no signature and never produce edges.
		if n.Meta == nil {
			continue
		}
		enc, ok := n.Meta[cloneSigMetaKey].(string)
		if !ok || enc == "" {
			continue
		}
		sig, ok := clones.DecodeSignature(enc)
		if !ok {
			continue
		}
		ci.lsh.Add(clones.Item{ID: n.ID, Sig: sig, TokenCount: tokensFromMeta(n)})
	}
	ci.built = true
}

// EvictFuncs removes a set of function/method nodes from the index: it
// decrements their shingles out of the CMS, drops them from the LSH index
// and the in-memory cache, and deletes their rows from the persisted
// sidecar. Called with the OLD function ids of a file just before that
// file's fresh nodes are added (UpdateFuncs), so a re-index is an
// evict-then-add of only the edited file's bodies.
func (ci *incrementalCloneIndex) EvictFuncs(g graph.Store, ids []string) {
	if ci == nil || len(ids) == 0 {
		return
	}
	ci.mu.Lock()
	defer ci.mu.Unlock()
	for _, id := range ids {
		sh, ok := ci.shingles[id]
		if !ok {
			// Not a tracked clone body (no signature / never added) —
			// still remove from the LSH index in case it was banked,
			// then move on.
			ci.lsh.Remove(id)
			continue
		}
		for _, s := range sh {
			ci.cms.Decrement(s)
		}
		delete(ci.shingles, id)
		ci.lsh.Remove(id)
		ci.corpus--
	}
	if w, ok := g.(graph.CloneShingleWriter); ok {
		_ = w.DeleteCloneShingles(ids)
	}
}

// UpdateFuncs banks the freshly-parsed function/method nodes of one file
// into the index and emits the EdgeSimilarTo edges their signatures imply.
// funcNodes carry the raw shingle set on Meta (cloneShinglesMetaKey,
// stamped by applyCloneSignatures during parse) — this method computes
// their signatures through the same kernel the batch pass uses, so the two
// paths agree exactly.
//
// Two phases. First every new body's shingles are folded into the CMS,
// cached, persisted, and the corpus count bumped — so the boilerplate
// threshold the signature kernel sees reflects the new corpus, matching
// finaliseCloneSignatures. Then each body's signature is computed, stamped
// on the node, banked into the LSH index, and queried for clone pairs;
// surviving pairs are materialised as symmetric EdgeSimilarTo edges (both
// directions, mirroring detectClonesAndEmitEdgesCtx).
func (ci *incrementalCloneIndex) UpdateFuncs(g graph.Store, repoPrefix string, funcNodes []*graph.Node, threshold float64) {
	if ci == nil || g == nil {
		return
	}
	ci.mu.Lock()
	defer ci.mu.Unlock()

	// Phase 1: fold every new body into the CMS + cache + sidecar and
	// bump the corpus count, so the boilerplate gate below sees the same
	// corpus the batch finalise would.
	rows := make(map[string][]uint64)
	type pending struct {
		node     *graph.Node
		shingles []uint64
	}
	var todo []pending
	for _, n := range funcNodes {
		if n == nil || n.Meta == nil {
			continue
		}
		if n.Kind != graph.KindFunction && n.Kind != graph.KindMethod {
			continue
		}
		sh, ok := n.Meta[cloneShinglesMetaKey].([]uint64)
		if !ok {
			continue
		}
		for _, s := range sh {
			ci.cms.Add(s)
		}
		ci.shingles[n.ID] = sh
		ci.corpus++
		rows[n.ID] = sh
		todo = append(todo, pending{node: n, shingles: sh})
	}
	if w, ok := g.(graph.CloneShingleWriter); ok && len(rows) > 0 {
		_ = w.BulkSetCloneShingles(repoPrefix, rows)
	}

	// Corpus-based gate, matching finaliseCloneSignatures exactly.
	useFilter := ci.corpus >= cmsMinCorpus
	var thr uint32
	if useFilter {
		thr = uint32(float64(ci.corpus) * cmsBoilerplateRatio)
		if thr < 1 {
			thr = 1
		}
	}

	// Phase 2: compute each signature, stamp it, bank it into the LSH
	// index, and remember the banked Item so we can query for pairs once
	// every new body is in the index. clone_shingles is removed from Meta
	// (the sidecar holds the durable copy) — mirrors finalise.
	added := make([]clones.Item, 0, len(todo))
	for _, p := range todo {
		n := p.node
		sig, ok := computeCloneSigFromShingles(ci.cms, thr, useFilter, p.shingles)
		delete(n.Meta, cloneShinglesMetaKey)
		if !ok {
			delete(n.Meta, cloneSigMetaKey)
			continue
		}
		n.Meta[cloneSigMetaKey] = clones.EncodeSignature(sig)
		item := clones.Item{ID: n.ID, Sig: sig, TokenCount: tokensFromMeta(n)}
		ci.lsh.Add(item)
		added = append(added, item)
	}

	// Emit edges for every clone pair touching a newly-added body. Both
	// endpoints are looked up and a symmetric EdgeSimilarTo pair is
	// emitted, mirroring detectClonesAndEmitEdgesCtx's emit. AddEdge
	// dedupes by edge key, so a pair surfaced from both of its endpoints
	// (when two new bodies in the same file are clones of each other)
	// collapses to one symmetric pair.
	for _, item := range added {
		for _, p := range ci.lsh.QueryPairs(item, threshold) {
			from := g.GetNode(p.A)
			to := g.GetNode(p.B)
			if from == nil || to == nil {
				continue
			}
			emitSimilarEdge(g, from, to, p.Similarity)
			emitSimilarEdge(g, to, from, p.Similarity)
		}
	}
}