package main

import (
	"context"
	"encoding/json"
	"fmt"
	"strings"

	"github.com/breel-render/spoc-bot-vr/model"
)

type Storage struct {
	driver Driver
}

func NewStorage(ctx context.Context, driver Driver) (Storage, error) {
	if _, err := driver.ExecContext(ctx, `
		CREATE TABLE IF NOT EXISTS events (ID TEXT UNIQUE);
		CREATE TABLE IF NOT EXISTS messages (ID TEXT UNIQUE);
		CREATE TABLE IF NOT EXISTS threads (ID TEXT UNIQUE);
	`); err != nil {
		return Storage{}, err
	}

	for table, v := range map[string]any{
		"events":   model.Event{},
		"messages": model.Message{},
		"threads":  model.Thread{},
	} {
		b, _ := json.Marshal(v)
		var m map[string]struct{}
		json.Unmarshal(b, &m)
		for k := range m {
			if k == `ID` {
				continue
			}
			driver.ExecContext(ctx, fmt.Sprintf(`ALTER TABLE %s ADD COLUMN %s TEXT`, table, k))
		}
	}

	return Storage{driver: driver}, nil
}

func (s Storage) GetEvent(ctx context.Context, ID string) (model.Event, error) {
	v := model.Event{}
	err := s.selectOne(ctx, "events", &v, "ID = $1", ID)
	return v, err
}

func (s Storage) UpsertEvent(ctx context.Context, event model.Event) error {
	return s.upsert(ctx, "events", event)
}

func (s Storage) GetMessage(ctx context.Context, ID string) (model.Message, error) {
	v := model.Message{}
	err := s.selectOne(ctx, "messages", &v, "ID = $1", ID)
	return v, err
}

func (s Storage) UpsertMessage(ctx context.Context, message model.Message) error {
	return s.upsert(ctx, "messages", message)
}

func (s Storage) GetThread(ctx context.Context, ID string) (model.Thread, error) {
	v := model.Thread{}
	err := s.selectOne(ctx, "threads", &v, "ID = $1", ID)
	return v, err
}

func (s Storage) UpsertThread(ctx context.Context, thread model.Thread) error {
	return s.upsert(ctx, "threads", thread)
}

func (s Storage) selectOne(ctx context.Context, table string, v any, clause string, args ...any) error {
	if questions := strings.Count(clause, "$"); questions != len(args) {
		return fmt.Errorf("expected %v args for clause but found %v", questions, len(args))
	}

	keys, _, _, _, err := keysArgsKeyargsValues(v)
	if err != nil {
		return err
	}

	for i := range args {
		args[i], _ = json.Marshal(args[i])
	}

	q := fmt.Sprintf(`
		SELECT %s FROM %s WHERE %s
	`, strings.Join(keys, ", "), table, clause)
	row := s.driver.QueryRowContext(ctx, q, args...)
	if err := row.Err(); err != nil {
		return err
	}

	scanTargets := make([]any, len(keys))
	for i := range scanTargets {
		scanTargets[i] = &[]byte{}
	}
	if err := row.Scan(scanTargets...); err != nil {
		return err
	}

	m := map[string]json.RawMessage{}
	for i, k := range keys {
		m[k] = *scanTargets[i].(*[]byte)
	}
	b, _ := json.Marshal(m)
	return json.Unmarshal(b, v)
}

func (s Storage) upsert(ctx context.Context, table string, v any) error {
	keys, args, keyArgs, values, err := keysArgsKeyargsValues(v)
	if err != nil || len(keys) == 0 {
		return err
	}

	q := fmt.Sprintf(`
		INSERT INTO %s (%s) VALUES (%s)
		ON CONFLICT (ID) DO UPDATE SET %s
	`, table, strings.Join(keys, ", "), strings.Join(args, ", "), strings.Join(keyArgs, ", "))
	if result, err := s.driver.ExecContext(ctx, q, values...); err != nil {
		return err
	} else if n, err := result.RowsAffected(); err != nil {
		return err
	} else if n != 1 {
		return fmt.Errorf("UpsertMessage affected %v rows", n)
	}
	return nil
}

func keysArgsKeyargsValues(v any) ([]string, []string, []string, []any, error) {
	b, _ := json.Marshal(v)
	var m map[string]json.RawMessage
	err := json.Unmarshal(b, &m)

	keys := []string{}
	for k := range m {
		keys = append(keys, k)
	}
	args := make([]string, len(keys))
	for i := range args {
		args[i] = fmt.Sprintf("$%d", i+1)
	}
	keyArgs := make([]string, len(keys))
	for i := range keyArgs {
		keyArgs[i] = fmt.Sprintf("%s=$%d", keys[i], i+1)
	}
	values := make([]any, len(keys))
	for i := range values {
		values[i] = []byte(m[keys[i]])
	}

	return keys, args, keyArgs, values, err
}