//  Copyright (c) 2016 Couchbase, Inc.
//  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 camelcase_filter

import (
	"github.com/blevesearch/bleve/analysis"
)

func buildTokenFromTerm(buffer []rune) *analysis.Token {
	return &analysis.Token{
		Term: analysis.BuildTermFromRunes(buffer),
	}
}

// Parser accepts a symbol and passes it to the current state (representing a class).
// The state can accept it (and accumulate it). Otherwise, the parser creates a new state that
// starts with the pushed symbol.
//
// Parser accumulates a new resulting token every time it switches state.
// Use FlushTokens() to get the results after the last symbol was pushed.
type Parser struct {
	bufferLen int
	buffer    []rune
	current   State
	tokens    []*analysis.Token
}

func NewParser(len int) *Parser {
	return &Parser{
		bufferLen: len,
		buffer:    make([]rune, 0, len),
		tokens:    make([]*analysis.Token, 0, len),
	}
}

func (p *Parser) Push(sym rune, peek *rune) {
	if p.current == nil {
		// the start of parsing
		p.current = p.NewState(sym)
		p.buffer = append(p.buffer, sym)

	} else if p.current.Member(sym, peek) {
		// same state, just accumulate
		p.buffer = append(p.buffer, sym)

	} else {
		// the old state is no more, thus convert the buffer
		p.tokens = append(p.tokens, buildTokenFromTerm(p.buffer))

		// let the new state begin
		p.current = p.NewState(sym)
		p.buffer = make([]rune, 0, p.bufferLen)
		p.buffer = append(p.buffer, sym)
	}
}

// Note. States have to have different starting symbols.
func (p *Parser) NewState(sym rune) State {
	var found State

	found = &LowerCaseState{}
	if found.StartSym(sym) {
		return found
	}

	found = &UpperCaseState{}
	if found.StartSym(sym) {
		return found
	}

	found = &NumberCaseState{}
	if found.StartSym(sym) {
		return found
	}

	return &NonAlphaNumericCaseState{}
}

func (p *Parser) FlushTokens() []*analysis.Token {
	p.tokens = append(p.tokens, buildTokenFromTerm(p.buffer))
	return p.tokens
}
