package db

import (
	"axolotl/models"
	"axolotl/parse"
	"database/sql"
	"fmt"
	"math/rand"
	"strings"
	"time"
)

func generateID() string {
	const chars = "abcdefghijklmnopqrstuvwxyz"
	b := make([]byte, 5)
	for i := range b {
		b[i] = chars[rand.Intn(26)]
	}
	return string(b)
}

func (db *DB) generateUniqueID() string {
	//TODO: Check if all ids are reserved
	for {
		id := generateID()
		var exists bool
		db.QueryRow("SELECT EXISTS(SELECT 1 FROM nodes WHERE id = ?)", id).Scan(&exists)
		if !exists {
			return id
		}
	}
}

type CreateParams struct {
	Title     string
	Content   string
	DueDate   string
	Type      string
	Status    string
	Priority  string
	Namespace string
	Tags      []string
	Rels      map[models.RelType][]string
}

func (db *DB) CreateNode(p CreateParams) (*models.Node, error) {
	tx, err := db.Begin()
	if err != nil {
		return nil, err
	}
	defer tx.Rollback()

	now := time.Now().UTC().Format(time.RFC3339)
	id := db.generateUniqueID()

	_, err = tx.Exec(
		"INSERT INTO nodes (id, title, content, due_date, created_at, updated_at) VALUES (?, ?, ?, ?, ?, ?)",
		id, p.Title, p.Content, p.DueDate, now, now,
	)
	if err != nil {
		return nil, err
	}

	tags := p.Tags
	if p.Type != "" {
		tags = append(tags, models.PropertyTag("type", p.Type))
	} else {
		tags = append(tags, models.PropertyTag("type", "issue"))
	}
	if p.Status != "" {
		tags = append(tags, models.PropertyTag("status", p.Status))
	}
	if p.Priority != "" {
		tags = append(tags, models.PropertyTag("prio", p.Priority))
	}
	ns := p.Namespace
	if ns == "" {
		ns = GetCurrentUser()
	}
	tags = append(tags, models.PropertyTag("namespace", ns))

	for _, tag := range tags {
		if _, err := tx.Exec("INSERT INTO tags (node_id, tag) VALUES (?, ?)", id, tag); err != nil {
			return nil, err
		}
	}

	for relType, targets := range p.Rels {
		for _, target := range targets {
			if _, err := tx.Exec(
				"INSERT INTO rels (from_id, to_id, rel_type) VALUES (?, ?, ?)",
				id, target, relType,
			); err != nil {
				return nil, err
			}
		}
	}

	allText := p.Title + " " + p.Content
	for _, u := range parse.Mentions(allText) {
		tx.Exec("INSERT INTO tags (node_id, tag) VALUES (?, ?)", id, models.PropertyTag("inbox", u))
	}

	if err := tx.Commit(); err != nil {
		return nil, err
	}

	return db.NodeByID(id)
}

type UpdateParams struct {
	Title      string
	Content    string
	DueDate    string
	ClearDue   bool
	Status     string
	Priority   string
	AddTags    []string
	RemoveTags []string
	AddRels    map[models.RelType][]string
	RemoveRels map[models.RelType][]string
}

func (db *DB) UpdateNode(id string, p UpdateParams) error {
	tx, err := db.Begin()
	if err != nil {
		return err
	}
	defer tx.Rollback()

	now := time.Now().UTC().Format(time.RFC3339)
	_, err = tx.Exec("UPDATE nodes SET updated_at = ? WHERE id = ?", now, id)
	if err != nil {
		return err
	}

	if p.Title != "" {
		_, err = tx.Exec("UPDATE nodes SET title = ? WHERE id = ?", p.Title, id)
		if err != nil {
			return err
		}
	}
	if p.Content != "" {
		_, err = tx.Exec("UPDATE nodes SET content = ? WHERE id = ?", p.Content, id)
		if err != nil {
			return err
		}
	}
	if p.DueDate != "" {
		_, err = tx.Exec("UPDATE nodes SET due_date = ? WHERE id = ?", p.DueDate, id)
		if err != nil {
			return err
		}
	}
	if p.ClearDue {
		_, err = tx.Exec("UPDATE nodes SET due_date = NULL WHERE id = ?", id)
		if err != nil {
			return err
		}
	}

	for _, tag := range p.AddTags {
		tx.Exec("INSERT OR IGNORE INTO tags (node_id, tag) VALUES (?, ?)", id, tag)
	}
	for _, tag := range p.RemoveTags {
		tx.Exec("DELETE FROM tags WHERE node_id = ? AND tag = ?", id, tag)
	}

	if p.Status != "" {
		tx.Exec("DELETE FROM tags WHERE node_id = ? AND tag LIKE '_status::%'", id)
		tx.Exec("INSERT INTO tags (node_id, tag) VALUES (?, ?)", id, models.PropertyTag("status", p.Status))
	}
	if p.Priority != "" {
		tx.Exec("DELETE FROM tags WHERE node_id = ? AND tag LIKE '_prio::%'", id)
		tx.Exec("INSERT INTO tags (node_id, tag) VALUES (?, ?)", id, models.PropertyTag("prio", p.Priority))
	}

	for relType, targets := range p.AddRels {
		for _, target := range targets {
			tx.Exec("INSERT OR IGNORE INTO rels (from_id, to_id, rel_type) VALUES (?, ?, ?)", id, target, relType)
		}
	}
	for relType, targets := range p.RemoveRels {
		for _, target := range targets {
			tx.Exec("DELETE FROM rels WHERE from_id = ? AND to_id = ? AND rel_type = ?", id, target, relType)
		}
	}

	return tx.Commit()
}

func (db *DB) DeleteNode(id string) error {
	_, err := db.Exec("DELETE FROM nodes WHERE id = ?", id)
	return err
}

type ListFilter struct {
	Type      string
	Status    string
	Priority  string
	Namespace string
	Tag       string
	Inbox     string
	Assignee  string
}

func (db *DB) ListNodes(f ListFilter) ([]*models.Node, error) {
	q := "SELECT DISTINCT n.id FROM nodes n"
	args := []interface{}{}
	joins := []string{}
	conds := []string{}

	if f.Type != "" {
		joins = append(joins, "JOIN tags t_type ON n.id = t_type.node_id")
		conds = append(conds, "t_type.tag = ?")
		args = append(args, models.PropertyTag("type", f.Type))
	}
	if f.Status != "" {
		joins = append(joins, "JOIN tags t_status ON n.id = t_status.node_id")
		conds = append(conds, "t_status.tag = ?")
		args = append(args, models.PropertyTag("status", f.Status))
	}
	if f.Priority != "" {
		joins = append(joins, "JOIN tags t_prio ON n.id = t_prio.node_id")
		conds = append(conds, "t_prio.tag = ?")
		args = append(args, models.PropertyTag("prio", f.Priority))
	}
	if f.Namespace != "" {
		joins = append(joins, "JOIN tags t_ns ON n.id = t_ns.node_id")
		conds = append(conds, "t_ns.tag = ?")
		args = append(args, models.PropertyTag("namespace", f.Namespace))
	}
	if f.Tag != "" {
		joins = append(joins, "JOIN tags t_tag ON n.id = t_tag.node_id")
		conds = append(conds, "t_tag.tag = ?")
		args = append(args, f.Tag)
	}
	if f.Inbox != "" {
		joins = append(joins, "JOIN tags t_inbox ON n.id = t_inbox.node_id")
		conds = append(conds, "t_inbox.tag = ?")
		args = append(args, models.PropertyTag("inbox", f.Inbox))
	}
	if f.Assignee != "" {
		joins = append(joins, "JOIN rels r_assign ON n.id = r_assign.from_id")
		conds = append(conds, "r_assign.to_id = ? AND r_assign.rel_type = ?")
		args = append(args, f.Assignee, models.RelAssignee)
	}

	if len(joins) > 0 {
		q += " " + strings.Join(joins, " ")
	}
	if len(conds) > 0 {
		q += " WHERE " + strings.Join(conds, " AND ")
	}
	q += " ORDER BY n.created_at DESC"

	rows, err := db.Query(q, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var nodes []*models.Node
	for rows.Next() {
		var id string
		if err := rows.Scan(&id); err != nil {
			return nil, err
		}
		n, err := db.NodeByID(id)
		if err != nil {
			return nil, err
		}
		nodes = append(nodes, n)
	}
	return nodes, nil
}

func (db *DB) CanClose(id string) (bool, []string, error) {
	rows, err := db.Query(
		"SELECT to_id FROM rels WHERE from_id = ? AND rel_type = ?",
		id, models.RelBlocks,
	)
	if err != nil {
		return false, nil, err
	}
	defer rows.Close()

	var blocking []string
	for rows.Next() {
		var blockerID string
		if err := rows.Scan(&blockerID); err != nil {
			return false, nil, err
		}
		var tag string
		err := db.QueryRow(
			"SELECT tag FROM tags WHERE node_id = ? AND tag LIKE '_status::%'",
			blockerID,
		).Scan(&tag)
		if err == sql.ErrNoRows {
			blocking = append(blocking, blockerID)
			continue
		}
		if err != nil {
			return false, nil, err
		}
		if strings.HasSuffix(tag, "::open") {
			blocking = append(blocking, blockerID)
		}
	}
	return len(blocking) == 0, blocking, nil
}

func (db *DB) GetAllUsers() ([]string, error) {
	rows, err := db.Query("SELECT n.id FROM nodes n JOIN tags t ON n.id = t.node_id WHERE t.tag = ?", models.PropertyTag("type", "user"))
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var users []string
	for rows.Next() {
		var id string
		rows.Scan(&id)
		users = append(users, id)
	}
	return users, nil
}

func (db *DB) GetSubtasks(parentID string) ([]*models.Node, error) {
	rows, err := db.Query(
		"SELECT to_id FROM rels WHERE from_id = ? AND rel_type = ?",
		parentID, models.RelSubtask,
	)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var nodes []*models.Node
	for rows.Next() {
		var id string
		rows.Scan(&id)
		n, err := db.NodeByID(id)
		if err != nil {
			return nil, err
		}
		nodes = append(nodes, n)
	}
	return nodes, nil
}

func ParseRelFlag(s string) (models.RelType, string, error) {
	parts := strings.SplitN(s, ":", 2)
	if len(parts) != 2 {
		return "", "", fmt.Errorf("invalid relation format: %s (expected type:id)", s)
	}
	return models.RelType(parts[0]), parts[1], nil
}