// Package brainstore is the concrete BrainStore: the single shared
// implementation of the #45 write/update/get verbs, used by BOTH the MCP
// handlers and the capture use-case so there is one implementation, not
// two (the Clean-Architecture / DRY payoff of #51).
//
// It composes the file-level primitives in package api (WriteNote,
// UpdateNote, ReadNote — the read-after-write contract) with the wiki
// upkeep that must accompany a write: wing _index rebuild, cross-wing
// auto-tunnel, and graph re-index. Embedding refresh is intentionally
// out-of-band (mtime-driven vectorstore.Sync) and not triggered here —
// see the brain note on out-of-band sync.
package brainstore

import (
	"context"
	"log/slog"
	"strings"

	"github.com/mathiasbq/hyperguild/ingestion/internal/api"
	"github.com/mathiasbq/hyperguild/ingestion/internal/brain"
	"github.com/mathiasbq/hyperguild/ingestion/internal/capture"
	"github.com/mathiasbq/hyperguild/ingestion/internal/graphsync"
)

// Store implements capture.BrainStore against a brain directory on disk,
// optionally re-indexing each write into the knowledge graph.
type Store struct {
	brainDir string
	graph    graphsync.Store // nil = graph re-index disabled
}

// New constructs a Store bound to brainDir with graph indexing disabled.
func New(brainDir string) *Store {
	return &Store{brainDir: brainDir}
}

// WithGraph enables graph re-index on every write/update. nil disables it.
func (s *Store) WithGraph(g graphsync.Store) *Store {
	s.graph = g
	return s
}

// Write creates a brain note and returns its read-after-write handle.
func (s *Store) Write(ctx context.Context, n capture.Note) (capture.Ref, error) {
	relPath, err := api.WriteNote(s.brainDir, api.WriteNoteOptions{
		Content:  n.Content,
		Filename: n.Filename,
		Type:     n.Type,
		Domain:   n.Domain,
		Wing:     n.Wing,
		Hall:     n.Hall,
	})
	if err != nil {
		return capture.Ref{}, err
	}
	s.wikiUpkeep(relPath, n.Wing, n.Content)
	s.indexInGraph(ctx, "brain_write", relPath)

	_, _, hash, _ := api.ReadNote(s.brainDir, relPath)
	return capture.Ref{ID: relPath, Path: relPath, ContentHash: hash}, nil
}

// Update supersedes an existing note in place. slug may be a bare slug
// (resolved against n.Wing/n.Hall) or a full brain-relative path (when it
// contains a slash). It never creates — a missing target is an error.
func (s *Store) Update(ctx context.Context, slug string, n capture.Note) (capture.Ref, error) {
	opts := api.UpdateNoteOptions{Content: n.Content, Reason: n.Reason}
	if strings.Contains(slug, "/") {
		opts.Path = slug
	} else {
		opts.Wing, opts.Hall, opts.Slug = n.Wing, n.Hall, slug
	}

	relPath, hash, _, err := api.UpdateNote(s.brainDir, opts)
	if err != nil {
		return capture.Ref{}, err
	}
	if wing := wingFromRelPath(relPath); wing != "" {
		s.wikiUpkeep(relPath, wing, n.Content)
	}
	s.indexInGraph(ctx, "brain_update", relPath)

	return capture.Ref{ID: relPath, Path: relPath, ContentHash: hash, Superseded: true}, nil
}

// Get fetches a note by id/path — the read-after-write confirmation
// primitive (a direct fetch, never a semantic query).
func (s *Store) Get(_ context.Context, id string) (capture.StoredNote, error) {
	fm, body, hash, err := api.ReadNote(s.brainDir, id)
	if err != nil {
		return capture.StoredNote{}, err
	}
	return capture.StoredNote{ID: id, Path: id, ContentHash: hash, Frontmatter: fm, Body: body}, nil
}

// wikiUpkeep rebuilds the wing _index and re-tunnels cross-wing matches
// when a note lands in the structured wiki. Both are best-effort: the
// note is already written, so a failure here is logged, not propagated.
func (s *Store) wikiUpkeep(relPath, wing, content string) {
	if wing == "" {
		return
	}
	if err := brain.BuildWingIndex(s.brainDir, wing); err != nil {
		slog.Warn("brainstore: auto-index failed", "wing", wing, "err", err)
	}
	if err := brain.AutoTunnel(s.brainDir, relPath, content); err != nil {
		slog.Warn("brainstore: auto-tunnel failed", "src", relPath, "err", err)
	}
}

// indexInGraph re-indexes a written doc into the graph, best-effort.
func (s *Store) indexInGraph(ctx context.Context, op, relPath string) {
	if s.graph == nil || relPath == "" {
		return
	}
	if err := graphsync.IndexDoc(ctx, s.graph, s.brainDir, relPath); err != nil {
		slog.Warn(op+": graph index failed", "path", relPath, "err", err)
	}
}

// wingFromRelPath extracts the wing from a structured wiki path
// (wiki/<wing>/<hall>/<slug>.md). Returns "" for legacy/non-wiki paths.
func wingFromRelPath(relPath string) string {
	parts := strings.Split(relPath, "/")
	if len(parts) >= 4 && parts[0] == "wiki" {
		return parts[1]
	}
	return ""
}