package soko

import (
	"errors"
	"fmt"
	"io"

	"opslag.de/schobers/krampus19/gut"
)

func ParseLevel(r io.Reader) (Level, error) {
	var l Level
	ctx := levelContext{&l}
	err := gut.ParseLines(r, ctx.parse)
	if err != nil {
		return Level{}, err
	}
	return l, nil
}

type levelContext struct {
	level *Level
}

func (c *levelContext) parse(p *gut.LineParser) gut.ParseLineFn {
	if p.EOF() {
		return nil
	}
	switch p.Peek() {
	case "level:":
		return c.parseContent
	case "":
		p.Next() // skip
		return c.parse
	default:
		return nil
	}
}

func (c *levelContext) parseContent(p *gut.LineParser) gut.ParseLineFn {
	if p.Next() != "level:" {
		return p.EmitErr(errors.New("expected level start"))
	}
	return c.parseRow
}

func (c *levelContext) parseRow(p *gut.LineParser) gut.ParseLineFn {
	if p.EOF() {
		return p.EmitErr(errors.New("unexpected end of file"))
	}
	line := p.Next()
	if line == ":level" {
		return c.parse
	}
	if c.level.Height == 0 {
		c.level.Width = len(line) / 2
	}
	return c.addRow(p, line)
}

func (c *levelContext) addRow(p *gut.LineParser, line string) gut.ParseLineFn {
	var tiles []Tile
	var entities []EntityType
	for i := 0; i < len(line); i += 2 {
		tiles = append(tiles, Tile(line[i]))
		entities = append(entities, EntityType(line[i+1]))
	}

	for i, t := range tiles {
		if !t.IsValid() {
			return p.EmitErr(fmt.Errorf("level contains invalid Tile at (%d, %d)", i, c.level.Height))
		}
	}
	for i, e := range entities {
		if !e.IsValid() {
			return p.EmitErr(fmt.Errorf("level contains invalid entity type at (%d, %d)", i, c.level.Height))
		}
	}

	c.level.Height++
	c.level.Tiles = append(c.level.Tiles, tiles...)
	c.level.Entities = append(c.level.Entities, entities...)

	return c.parseRow
}