package platform

import (
	"encoding/json"
	"net/http"
	"sort"
	"time"
)

func (s *service) dissolveSubgraph(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
	}
	key := canvasIdempotencyKey(r)
	frame := r.PathValue("frame")
	if !uuidSlugPattern.MatchString(key) || !canvasID.MatchString(frame) {
		reject(w, 400, "invalid_subgraph_request")
		return nil
	}
	var input struct {
		ExpectedVersions map[string]int64 `json:"expected_versions"`
	}
	if !decode(w, r, &input) {
		return nil
	}
	if len(input.ExpectedVersions) == 0 {
		reject(w, 428, "version_required")
		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")
	_, role, err := lockMaterial(r.Context(), tx, project, workspace, board, account)
	if err != nil {
		return err
	}
	if role == "viewer" {
		reject(w, 403, "forbidden")
		return nil
	}
	action := "dissolve_subgraph/" + frame
	hash := payloadDigest(input)
	done, err := transactionRetry(w, r, tx, project, account, board, action, key, hash)
	if err != nil {
		return err
	}
	if done {
		return nil
	}
	var child string
	err = tx.QueryRowContext(r.Context(), `SELECT child_board_id::text FROM canvas_subgraphs WHERE project=$1 AND workspace_id=$2 AND parent_board_id=$3 AND frame_id=$4 AND archived_at IS NULL`, project, workspace, board, frame).Scan(&child)
	if err != nil {
		return err
	}
	relation, err := readSubgraphRelation(r, tx, project, workspace, child)
	if err != nil {
		return err
	}
	archivedRelation := relation
	archivedRelation.Archived = true
	changes := []subgraphRelationChange{{Before: relation, After: archivedRelation}}
	participants := []string{board, child}
	rows, err := tx.QueryContext(r.Context(), `SELECT child_board_id::text FROM canvas_subgraphs WHERE project=$1 AND workspace_id=$2 AND parent_board_id=$3 AND archived_at IS NULL ORDER BY child_board_id`, project, workspace, child)
	if err != nil {
		return err
	}
	nested := []string{}
	for rows.Next() {
		var id string
		if err = rows.Scan(&id); err != nil {
			rows.Close()
			return err
		}
		nested = append(nested, id)
	}
	err = rows.Err()
	rows.Close()
	if err != nil {
		return err
	}
	for _, id := range nested {
		before, err := readSubgraphRelation(r, tx, project, workspace, id)
		if err != nil {
			return err
		}
		after := before
		after.Parent = board
		changes = append(changes, subgraphRelationChange{Before: before, After: after})
		participants = append(participants, id)
	}
	parentBefore, err := loadCanvas(r, tx, project, workspace, board)
	if err != nil {
		return err
	}
	childBefore, err := loadCanvas(r, tx, project, workspace, child)
	if err != nil {
		return err
	}
	members := []string{}
	for node := range canvasNodeData(childBefore.Document) {
		members = append(members, node)
	}
	repair, err := planAncestorPortRepair(r, tx, project, workspace, board, child, account, members, parentBefore.Document)
	if err != nil {
		return err
	}
	if repair != nil {
		participants = append(participants, repair.Ancestor)
	}
	sort.Strings(participants)
	if len(input.ExpectedVersions) != len(participants) {
		reject(w, 428, "version_required")
		return nil
	}
	snapshots := map[string]canvasSnapshot{}
	beforeSnapshots := []canvasSnapshot{}
	for _, id := range participants {
		_, role, err := lockMaterial(r.Context(), tx, project, workspace, id, account)
		if err != nil {
			return err
		}
		if role == "viewer" {
			reject(w, 403, "forbidden")
			return nil
		}
		snapshot, err := loadCanvas(r, tx, project, workspace, id)
		if err != nil {
			return err
		}
		if _, exists := input.ExpectedVersions[id]; !exists {
			reject(w, 428, "version_required")
			return nil
		}
		if input.ExpectedVersions[id] != snapshot.Version {
			reject(w, 412, "version_conflict")
			return nil
		}
		snapshots[id] = snapshot
		beforeSnapshots = append(beforeSnapshots, snapshot)
	}
	parent, childSnapshot := snapshots[board], snapshots[child]
	parentDoc, childDoc, err := dissolveDocuments(parent.Document, childSnapshot.Document, frame)
	if err != nil {
		if err == errGraphOwnership {
			reject(w, 409, "ownership_conflict")
		} else {
			reject(w, 413, "graph_limit_exceeded")
		}
		return nil
	}
	if repair != nil {
		documents := map[string]json.RawMessage{board: parentDoc, repair.Ancestor: snapshots[repair.Ancestor].Document}
		if err = applyAncestorPortRepair(repair, board, board, documents); err != nil {
			return err
		}
		parentDoc = documents[board]
		ancestor := snapshots[repair.Ancestor]
		ancestor.Document = documents[repair.Ancestor]
		snapshots[repair.Ancestor] = ancestor
	}
	parent.Document = parentDoc
	childSnapshot.Document = childDoc
	snapshots[board] = parent
	snapshots[child] = childSnapshot
	// Reparent nested children first. The archived child keeps a recovery record,
	// while live ownership immediately follows the nodes flattened into the parent.
	for i := len(changes) - 1; i >= 0; i-- {
		if err = writeSubgraphRelation(r, tx, project, workspace, changes[i].After); err != nil {
			return err
		}
	}
	updated := []canvasSnapshot{}
	versions := map[string]int64{}
	for _, id := range participants {
		snapshot := snapshots[id]
		snapshot.Version++
		if err = s.saveCanvas(r, tx, project, workspace, snapshot); err != nil {
			return err
		}
		updated = append(updated, snapshot)
		versions[id] = snapshot.Version
		snapshots[id] = snapshot
	}
	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": snapshots[board], "snapshots": updated, "archived_board_ids": []string{child}, "undo_receipt": response{"transaction_id": id, "valid_for_seconds": 604800, "expires_at": receiptExpiry}}
	encoded, _ := json.Marshal(result)
	beforeJSON, _ := json.Marshal(beforeSnapshots)
	versionsJSON, _ := json.Marshal(versions)
	relationsJSON, _ := json.Marshal(changes)
	_, 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,relation_changes) VALUES($1,$2,$3,$4,$5,$6,$7,$8,200,$9,$10,$11,$12)`, project, workspace, board, id, account, action, key, hash, encoded, beforeJSON, versionsJSON, relationsJSON)
	if err != nil {
		return err
	}
	if err = tx.Commit(); err != nil {
		return err
	}
	setVersion(w, versions[board])
	reply(w, 200, result)
	return nil
}