package db

import (
	"context"
	"database/sql"
	"errors"

	"mind/internal/models"
)

type Repo struct { db *sql.DB }

func NewRepo(db *sql.DB) *Repo { return &Repo{db: db} }

// Conversations
func (r *Repo) CreateConversation(ctx context.Context, ownerID int64, title string) (int64, error) {
	res, err := r.db.ExecContext(ctx, `INSERT INTO conversations(owner_id,title) VALUES(?,?)`, ownerID, title)
	if err != nil { return 0, err }
	return res.LastInsertId()
}

func (r *Repo) ListConversations(ctx context.Context, ownerID int64) ([]models.Conversation, error) {
	rows, err := r.db.QueryContext(ctx, `SELECT id, owner_id, title, created_at FROM conversations WHERE owner_id=? ORDER BY id DESC`, ownerID)
	if err != nil { return nil, err }
	defer rows.Close()
	var out []models.Conversation
	for rows.Next() {
		var c models.Conversation
		if err := rows.Scan(&c.ID, &c.OwnerID, &c.Title, &c.Created); err != nil { return nil, err }
		out = append(out, c)
	}
	return out, nil
}

// Nodes & Edges
func (r *Repo) CreateNode(ctx context.Context, convID int64, authorKind, content string) (int64, error) {
	res, err := r.db.ExecContext(ctx, `INSERT INTO nodes(conversation_id,author_kind,content) VALUES(?,?,?)`, convID, authorKind, content)
	if err != nil { return 0, err }
	return res.LastInsertId()
}

func (r *Repo) Link(ctx context.Context, parentID, childID int64) error {
	_, err := r.db.ExecContext(ctx, `INSERT INTO edges(parent_id,child_id) VALUES(?,?)`, parentID, childID)
	return err
}

func (r *Repo) GetNode(ctx context.Context, id int64) (models.Node, error) {
	var n models.Node
	err := r.db.QueryRowContext(ctx, `SELECT id,conversation_id,author_kind,content,created_at FROM nodes WHERE id=?`, id).
		Scan(&n.ID, &n.ConversationID, &n.AuthorKind, &n.Content, &n.Created)
	return n, err
}

// Branches
func (r *Repo) CreateOrGetBranch(ctx context.Context, convID int64, name string, headNodeID int64) (models.Branch, error) {
	// Try insert
	_, _ = r.db.ExecContext(ctx, `INSERT INTO branches(conversation_id,name,head_node_id) VALUES(?,?,?)`, convID, name, headNodeID)
	return r.GetBranch(ctx, convID, name)
}

func (r *Repo) GetBranch(ctx context.Context, convID int64, name string) (models.Branch, error) {
	var b models.Branch
	err := r.db.QueryRowContext(ctx, `SELECT id,conversation_id,name,head_node_id FROM branches WHERE conversation_id=? AND name=?`, convID, name).
		Scan(&b.ID, &b.ConversationID, &b.Name, &b.HeadNodeID)
	return b, err
}

func (r *Repo) MoveBranchHead(ctx context.Context, branchID, newHeadID int64) error {
	_, err := r.db.ExecContext(ctx, `UPDATE branches SET head_node_id=? WHERE id=?`, newHeadID, branchID)
	return err
}

// Latest-parent walk for linearize
func (r *Repo) LatestParent(ctx context.Context, childID int64) (models.Node, bool, error) {
	row := r.db.QueryRowContext(ctx, `
		SELECT n.id,n.conversation_id,n.author_kind,n.content,n.created_at
		FROM edges e
		JOIN nodes n ON n.id=e.parent_id
		WHERE e.child_id=?
		ORDER BY n.created_at DESC
		LIMIT 1`, childID)
	var n models.Node
	if err := row.Scan(&n.ID, &n.ConversationID, &n.AuthorKind, &n.Content, &n.Created); err != nil {
		if errors.Is(err, sql.ErrNoRows) { return models.Node{}, false, nil }
		return models.Node{}, false, err
	}
	return n, true, nil
}

func (r *Repo) DeleteBranch(ctx context.Context, convID int64, name string) error {
    _, err := r.db.ExecContext(ctx, `DELETE FROM branches WHERE conversation_id=? AND name=?`, convID, name)
    return err
}

// ListBranches returns all branches for a conversation, newest first.
func (r *Repo) ListBranches(ctx context.Context, convID int64) ([]models.Branch, error) {
	rows, err := r.db.QueryContext(ctx, `
		SELECT id, conversation_id, name, head_node_id
		FROM branches
		WHERE conversation_id=?
		ORDER BY id DESC`, convID)
	if err != nil { return nil, err }
	defer rows.Close()

	var out []models.Branch
	for rows.Next() {
		var b models.Branch
		if err := rows.Scan(&b.ID, &b.ConversationID, &b.Name, &b.HeadNodeID); err != nil {
			return nil, err
		}
		out = append(out, b)
	}
	return out, nil
}