package platform

import (
	"crypto/sha256"
	"database/sql"
	"encoding/hex"
	"encoding/json"
	"net/http"
	"time"
)

func transactionRetry(w http.ResponseWriter, r *http.Request, tx *sql.Tx, project, account, board, action, key, hash string) (bool, error) {
	var previousHash string
	var status int
	var previous json.RawMessage
	err := tx.QueryRowContext(r.Context(), `SELECT payload_hash,response_status,response_body FROM canvas_transactions WHERE project=$1 AND account_id=$2 AND board_id=$3 AND action=$4 AND idempotency_key=$5 AND workspace_id=$6`, project, account, board, action, key, r.PathValue("workspace")).Scan(&previousHash, &status, &previous)
	if err == sql.ErrNoRows {
		return false, nil
	}
	if err != nil {
		return false, err
	}
	if hash != previousHash {
		reject(w, 409, "idempotency_conflict")
		return true, nil
	}
	var result struct {
		Parent canvasSnapshot `json:"parent"`
	}
	_ = json.Unmarshal(previous, &result)
	if result.Parent.Version > 0 {
		setVersion(w, result.Parent.Version)
	}
	reply(w, status, previous)
	return true, nil
}
func payloadDigest(v any) string {
	raw, _ := json.Marshal(v)
	h := sha256.Sum256(raw)
	return hex.EncodeToString(h[:])
}
func (s *service) saveCanvas(r *http.Request, tx *sql.Tx, project, workspace string, snapshot canvasSnapshot) error {
	var before json.RawMessage
	if err := tx.QueryRowContext(r.Context(), `SELECT COALESCE(canvas_document,'{"schema_version":1,"nodes":[],"edges":[],"viewport":{"x":0,"y":0,"zoom":1}}'::jsonb) FROM materials WHERE project=$1 AND workspace_id=$2 AND id=$3 FOR UPDATE`, project, workspace, snapshot.BoardID).Scan(&before); err != nil {
		return err
	}
	root, err := canonicalRoot(r.Context(), tx, project, workspace, snapshot.BoardID)
	if err != nil {
		return err
	}
	// Canonical lifecycle invalidation runs once against normalized identities.
	// Its compatibility projection must not mistake an owner move for deletion.
	if root == "" {
		if err := invalidateCanvasAITargets(r, tx, project, workspace, snapshot.BoardID, before, snapshot.Document); err != nil {
			return err
		}
	}

	if err := s.attachCanvasAssets(r, tx, project, workspace, snapshot.BoardID, snapshot.Document); err != nil {
		return err
	}
	_, err = tx.ExecContext(r.Context(), `UPDATE materials SET canvas_document=$4,canvas_version=$5 WHERE project=$1 AND workspace_id=$2 AND id=$3`, project, workspace, snapshot.BoardID, snapshot.Document, snapshot.Version)
	return err
}

func (s *service) migrateSubgraphs(w http.ResponseWriter, r *http.Request, project, account string) error {
	if r.Method != http.MethodPost {
		reject(w, 405, "method_not_allowed")
		return nil
	}
	if !acceptsCanvasV2(r) {
		reject(w, 409, "canvas_schema_upgrade_required")
		return nil
	}
	var input struct {
		DryRun *bool  `json:"dry_run"`
		PlanID string `json:"plan_id"`
	}
	if !decode(w, r, &input) {
		return nil
	}
	if input.DryRun == nil {
		reject(w, 400, "invalid_migration_request")
		return nil
	}
	key := canvasIdempotencyKey(r)
	var expected int64
	if !*input.DryRun {
		if !uuidSlugPattern.MatchString(key) {
			reject(w, 400, "invalid_idempotency_key")
			return nil
		}
		var ok bool
		expected, ok = expectedVersion(w, r)
		if !ok {
			return nil
		}
	}
	tx, err := s.db.BeginTx(r.Context(), nil)
	if err != nil {
		return err
	}
	defer tx.Rollback()
	workspace, board := r.PathValue("workspace"), r.PathValue("material")
	kind, role, err := lockMaterial(r.Context(), tx, project, workspace, board, account)
	if err != nil {
		return err
	}
	if kind != "board" {
		reject(w, 400, "invalid_material")
		return nil
	}
	if role == "viewer" {
		reject(w, 403, "forbidden")
		return nil
	}
	if !*input.DryRun {
		done, err := transactionRetry(w, r, tx, project, account, board, "migrate_subgraphs", key, payloadDigest(input))
		if err != nil {
			return err
		}
		if done {
			return nil
		}
	}
	parent, err := loadCanvas(r, tx, project, workspace, board)
	if err != nil {
		return err
	}
	plan := legacyPlan(project, workspace, parent)
	// Preflight runs the actual transform with placeholder canonical IDs. It
	// never inserts materials or relation records.
	placeholders := map[string]string{}
	for _, f := range plan.Frames {
		placeholders[f.FrameID] = "00000000-0000-0000-0000-000000000000"
	}
	if len(placeholders) > 0 {
		if _, _, err := migrateLegacyDocument(parent.Document, placeholders); err != nil {
			plan.Issues = append(plan.Issues, "invalid_geometry_or_capacity")
		}
	}
	var depth int
	err = tx.QueryRowContext(r.Context(), `WITH RECURSIVE ancestors AS (SELECT $3::uuid AS id,0 AS depth UNION ALL SELECT s.parent_board_id,a.depth+1 FROM ancestors a JOIN canvas_subgraphs s ON s.project=$1 AND s.workspace_id=$2 AND s.child_board_id=a.id WHERE a.depth<8 AND s.archived_at IS NULL) SELECT max(depth) FROM ancestors`, project, workspace, board).Scan(&depth)
	if err != nil {
		return err
	}
	if depth >= 8 && plan.ChildCount > 0 {
		plan.Issues = append(plan.Issues, "subgraph_depth_exceeded")
	}
	if *input.DryRun {
		setVersion(w, parent.Version)
		reply(w, 200, plan)
		return nil
	}
	if expected != parent.Version || input.PlanID != plan.PlanID {
		reject(w, 412, "version_conflict")
		return nil
	}
	if len(plan.Issues) > 0 {
		reply(w, 413, response{"error": "graph_limit_exceeded", "details": plan.Issues})
		return nil
	}
	before := parent
	children := map[string]string{}
	childInfo := []any{}
	nodeData := canvasNodeData(parent.Document)
	for _, frame := range plan.Frames {
		var child, slug string
		err = tx.QueryRowContext(r.Context(), `INSERT INTO materials(project,workspace_id,kind,title,created_by) VALUES($1,$2,'board',$3,$4) RETURNING id::text,slug`, project, workspace, nodeData[frame.FrameID]["title"], account).Scan(&child, &slug)
		if err != nil {
			return err
		}
		source, _ := json.Marshal(response{"frame_id": frame.FrameID, "source_digest": plan.SourceDigest})
		_, err = tx.ExecContext(r.Context(), `INSERT INTO canvas_subgraphs(project,workspace_id,parent_board_id,frame_id,child_board_id,migration_source) VALUES($1,$2,$3,$4,$5,$6)`, project, workspace, board, frame.FrameID, child, source)
		if err != nil {
			return err
		}
		children[frame.FrameID] = child
		childInfo = append(childInfo, response{"frame_id": frame.FrameID, "id": child, "slug": slug, "workspace_id": workspace})
	}
	snapshots := []canvasSnapshot{}
	versions := map[string]int64{board: parent.Version}
	if len(children) > 0 {
		migrated, documents, err := migrateLegacyDocument(parent.Document, children)
		if err != nil {
			return err
		}
		parent.Document = migrated
		parent.Version++
		if err = s.saveCanvas(r, tx, project, workspace, parent); err != nil {
			return err
		}
		versions[board] = parent.Version
		for _, f := range plan.Frames {
			child := canvasSnapshot{BoardID: children[f.FrameID], Version: 1, Document: documents[f.FrameID]}
			if err = s.saveCanvas(r, tx, project, workspace, child); err != nil {
				return err
			}
			snapshots = append(snapshots, child)
			versions[child.BoardID] = 1
		}
	}
	var id string
	var receiptExpiry time.Time
	err = tx.QueryRowContext(r.Context(), `SELECT gen_random_uuid()::text,now()+interval '7 days'`).Scan(&id, &receiptExpiry)
	if err != nil {
		return err
	}
	result := response{"transaction_id": id, "parent": parent, "children": snapshots, "child_boards": childInfo, "plan": plan, "migrated_count": len(children), "undo_receipt": response{"transaction_id": id, "valid_for_seconds": 604800, "expires_at": receiptExpiry}}
	responseJSON, _ := json.Marshal(result)
	beforeJSON, _ := json.Marshal([]canvasSnapshot{before})
	versionsJSON, _ := json.Marshal(versions)
	_, err = tx.ExecContext(r.Context(), `INSERT INTO canvas_transactions(project,workspace_id,board_id,id,account_id,action,idempotency_key,payload_hash,response_status,response_body,before_state,after_versions) VALUES($1,$2,$3,$4,$5,'migrate_subgraphs',$6,$7,200,$8,$9,$10)`, project, workspace, board, id, account, key, payloadDigest(input), responseJSON, beforeJSON, versionsJSON)
	if err != nil {
		return err
	}
	if err = tx.Commit(); err != nil {
		return err
	}
	setVersion(w, parent.Version)
	reply(w, 200, result)
	return nil
}