// Copyright 2014 The Cayley Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package sexp

// Defines a running session of the sexp query language.

import (
	"context"
	"errors"
	"fmt"
	"sort"

	"github.com/cayleygraph/cayley/graph"
	"github.com/cayleygraph/cayley/query"
)

const Name = "sexp"

func init() {
	query.RegisterLanguage(query.Language{
		Name: Name,
		Session: func(qs graph.QuadStore) query.Session {
			return NewSession(qs)
		},
		REPL: func(qs graph.QuadStore) query.REPLSession {
			return NewSession(qs)
		},
	})
}

type Session struct {
	qs graph.QuadStore
}

func NewSession(qs graph.QuadStore) *Session {
	return &Session{qs: qs}
}

func (s *Session) Parse(input string) error {
	var parenDepth int
	for i, x := range input {
		if x == '(' {
			parenDepth++
		}
		if x == ')' {
			parenDepth--
			if parenDepth < 0 {
				min := 0
				if (i - 10) > min {
					min = i - 10
				}
				return fmt.Errorf("too many close parentheses at char %d: %s", i, input[min:i])
			}
		}
	}
	if parenDepth > 0 {
		return query.ErrParseMore
	}
	if len(ParseString(input)) > 0 {
		return nil
	}
	return errors.New("invalid syntax")
}

func (s *Session) Execute(ctx context.Context, input string, out chan query.Result, limit int) {
	defer close(out)
	it := BuildIteratorTreeForQuery(s.qs, input)
	err := graph.Iterate(ctx, it).Paths(true).Limit(limit).TagEach(func(tags map[string]graph.Value) {
		select {
		case out <- query.TagMapResult(tags):
		case <-ctx.Done():
		}
	})
	if err != nil {
		select {
		case out <- query.ErrorResult(err):
		case <-ctx.Done():
		}
	}
}

func (s *Session) FormatREPL(result query.Result) string {
	out := fmt.Sprintln("****")
	tags, ok := result.Result().(map[string]graph.Value)
	if !ok {
		return ""
	}
	tagKeys := make([]string, len(tags))
	i := 0
	for k := range tags {
		tagKeys[i] = k
		i++
	}
	sort.Strings(tagKeys)
	for _, k := range tagKeys {
		if k == "$_" {
			continue
		}
		out += fmt.Sprintf("%s : %s\n", k, s.qs.NameOf(tags[k]))
	}
	return out
}