package platform

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

type canvasSnapshot struct {
	BoardID  string          `json:"board_id"`
	Version  int64           `json:"version"`
	Document json.RawMessage `json:"document"`
}

func loadCanvas(r *http.Request, tx *sql.Tx, project, workspace, board string) (canvasSnapshot, error) {
	result := canvasSnapshot{BoardID: board}
	err := tx.QueryRowContext(r.Context(), `SELECT canvas_version,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, board).Scan(&result.Version, &result.Document)
	return result, err
}

func (s *service) createSubgraph(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)
	if !uuidSlugPattern.MatchString(key) {
		reject(w, 400, "invalid_idempotency_key")
		return nil
	}
	expected, ok := expectedVersion(w, r)
	if !ok {
		return nil
	}
	var input struct {
		Frame struct {
			ID        string         `json:"id"`
			Title     string         `json:"title"`
			Position  map[string]any `json:"position"`
			Width     float64        `json:"width"`
			Height    float64        `json:"height"`
			LabelMode string         `json:"labelMode"`
		} `json:"frame"`
	}
	if !decode(w, r, &input) {
		return nil
	}
	f := input.Frame
	if !canvasID.MatchString(f.ID) || !canvasString(f.Title, 300) || !canvasPoint(f.Position) || !canvasNumber(f.Width, 32, 100000) || !canvasNumber(f.Height, 32, 100000) || !canvasChoice(f.LabelMode, "hidden", "fixed", "scaled") {
		reject(w, 400, "invalid_canvas")
		return nil
	}
	payload, _ := json.Marshal(input)
	digest := sha256.Sum256(payload)
	hash := hex.EncodeToString(digest[:])
	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
	}
	var previousHash string
	var previous json.RawMessage
	var status int
	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='create_subgraph' AND idempotency_key=$4 AND workspace_id=$5`, project, account, board, key, workspace).Scan(&previousHash, &status, &previous)
	if err == nil {
		if previousHash != hash {
			reject(w, 409, "idempotency_conflict")
			return nil
		}
		var result struct {
			Parent canvasSnapshot `json:"parent"`
		}
		_ = json.Unmarshal(previous, &result)
		setVersion(w, result.Parent.Version)
		reply(w, status, previous)
		return nil
	}
	if err != sql.ErrNoRows {
		return err
	}
	parent, err := loadCanvas(r, tx, project, workspace, board)
	if err != nil {
		return err
	}
	if expected != parent.Version {
		reject(w, 412, "version_conflict")
		return nil
	}
	var doc map[string]any
	if err = json.Unmarshal(parent.Document, &doc); err != nil {
		return err
	}
	nodes := doc["nodes"].([]any)
	for _, v := range nodes {
		if v.(map[string]any)["id"] == f.ID {
			reject(w, 409, "ownership_conflict")
			return nil
		}
	}
	if len(nodes) >= 500 {
		reject(w, 413, "graph_limit_exceeded")
		return nil
	}
	var childID, slug string
	err = tx.QueryRowContext(r.Context(), `INSERT INTO materials(project,workspace_id,kind,title,created_by,canvas_document) VALUES($1,$2,'board',$3,$4,'{"schema_version":2,"nodes":[],"edges":[],"viewport":{"x":0,"y":0,"zoom":1}}') RETURNING id::text,slug`, project, workspace, f.Title, account).Scan(&childID, &slug)
	if err != nil {
		return err
	}
	if err = validateSubgraphPlacement(r, tx, project, workspace, board, childID); err != nil {
		return err
	}
	_, err = tx.ExecContext(r.Context(), `INSERT INTO canvas_subgraphs(project,workspace_id,parent_board_id,frame_id,child_board_id) VALUES($1,$2,$3,$4,$5)`, project, workspace, board, f.ID, childID)
	if err != nil {
		return err
	}
	node := map[string]any{"id": f.ID, "type": "frame", "position": f.Position, "width": f.Width, "height": f.Height, "data": map[string]any{
		"kind": "frame", "title": f.Title, "text": "", "rotation": 0, "labelMode": f.LabelMode,
		"subgraph": map[string]any{"boardId": childID}, "ports": []any{},
		"presentation": map[string]any{"collapsed": false, "contentScale": 1, "expandedSize": map[string]any{"width": f.Width, "height": f.Height}, "collapsedSize": map[string]any{"width": 240, "height": 140}},
	}}
	doc["nodes"] = append(nodes, node)
	doc["schema_version"] = 2
	raw, _ := json.Marshal(doc)
	if len(raw) > canvasLimit {
		reject(w, 413, "canvas_too_large")
		return nil
	}
	normalized, ok := normalizeCanvas(raw)
	if !ok {
		reject(w, 400, "invalid_canvas")
		return nil
	}
	before := parent
	parent.Document = normalized
	parent.Version++
	_, 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, board, parent.Document, parent.Version)
	if err != nil {
		return err
	}
	child, err := loadCanvas(r, tx, project, workspace, childID)
	if err != nil {
		return err
	}
	var transaction string
	var receiptExpiry time.Time
	err = tx.QueryRowContext(r.Context(), `SELECT gen_random_uuid()::text,now()+interval '7 days'`).Scan(&transaction, &receiptExpiry)
	if err != nil {
		return err
	}
	result := response{"transaction_id": transaction, "frame_id": f.ID, "child_board": response{"id": childID, "slug": slug, "workspace_id": workspace}, "parent": parent, "child": child, "undo_receipt": response{"transaction_id": transaction, "valid_for_seconds": 604800, "expires_at": receiptExpiry}}
	encoded, _ := json.Marshal(result)
	savedBefore, _ := json.Marshal([]canvasSnapshot{before})
	versions, _ := json.Marshal(map[string]int64{board: parent.Version, childID: child.Version})
	_, 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,'create_subgraph',$6,$7,201,$8,$9,$10)`, project, workspace, board, transaction, account, key, hash, encoded, savedBefore, versions)
	if err != nil {
		return err
	}
	if err = tx.Commit(); err != nil {
		return err
	}
	setVersion(w, parent.Version)
	reply(w, 201, result)
	return nil
}