// Package gemtext provides a variety of tools for processing gemtext files.
package gemtext

import (
	"fmt"
	"strings"
)

type ObjectType int64

const (
	TEXT ObjectType = iota
	LINK
	PREFORMATTED_TOGGLE
	PREFORMATTED_TEXT
	HEADING
	LIST
	QUOTE
)

// type GemtextObject represents a gemtext object.
type GemtextObject struct {
	Type    ObjectType
	Text    string // Contains the text of the element. For a link this is the label.
	Literal string // Contains the line as it exists in the file
	Path    string // Populated if object is a link
	Level   int    // Populated if object is a heading
}

// type GemtextPage represents a gemtext page. It is equivalent to a slice of GemtextObjects.
type GemtextPage []GemtextObject

// ParseLink takes a gemini link as a string and returns a GemtextObject and an error.
func ParseLink(l string) (GemtextObject, error) {
	if !strings.HasPrefix(l, "=>") {
		return GemtextObject{}, fmt.Errorf("Not a gemtext link!")
	} else {
		f := strings.Fields(l[2:])
		link := GemtextObject{Type: LINK, Literal: l}
		link.Path = f[0]
		link.Text = strings.TrimSpace(l[3+len(f[0]):]) // text that remains after removing the URL and link marker
		return link, nil
	}

}

// ParseHeading parses a gemtext heading, returns a HEADING GemtextObject if it is between levels 1-3 and TEXT otherwise.
func ParseHeading(l string) (GemtextObject, error) {
	switch {
	case strings.HasPrefix(l, "####"): // Fake headings
		return GemtextObject{Type: TEXT, Text: l, Literal: l}, nil
	case strings.HasPrefix(l, "###"):
		return GemtextObject{Type: HEADING, Level: 3, Text: strings.TrimSpace(l[3:]), Literal: l}, nil
	case strings.HasPrefix(l, "##"):
		return GemtextObject{Type: HEADING, Level: 2, Text: strings.TrimSpace(l[2:]), Literal: l}, nil
	case strings.HasPrefix(l, "#"):
		return GemtextObject{Type: HEADING, Level: 1, Text: strings.TrimSpace(l[1:]), Literal: l}, nil
	}
	return GemtextObject{Type: TEXT, Text: l, Literal: l}, nil

}

// ParseLine parses a gemtext line, and returns a GemtextObject representing it.
// "isPreformatted" takes a true if the line is in a preformatted block, else otherwise.
func ParseLine(line string, isPreformatted bool) (GemtextObject, error) {
	if !isPreformatted {
		switch {
		case strings.HasPrefix(line, "=>"):
			return ParseLink(line)
		case strings.HasPrefix(line, "```"):
			return GemtextObject{Type: PREFORMATTED_TOGGLE, Literal: line, Text: line[3:]}, nil
		case strings.HasPrefix(line, "#"):
			return ParseHeading(line)
		case strings.HasPrefix(line, ">"):
			return GemtextObject{Type: QUOTE, Text: strings.TrimSpace(line[1:]), Literal: line}, nil
		case strings.HasPrefix(line, "* "): // Bullets require a space in the spec
			return GemtextObject{Type: LIST, Text: line[2:], Literal: line}, nil
		}
		return GemtextObject{Type: TEXT, Text: line, Literal: line}, nil
	} else {
		if strings.HasPrefix(line, "```") { // toggles are the only special line type in preformatted mode
			return GemtextObject{Type: PREFORMATTED_TOGGLE, Literal: line, Text: line[3:]}, nil
		}
		return GemtextObject{Type: PREFORMATTED_TEXT, Text: line, Literal: line}, nil
	}

}

// ParsePage takes a string containing the contents of a gemtext page and returns a GemtextPage.
func ParsePage(p string) (GemtextPage, error) {
	preformatted := false
	lines := strings.Split(p, "\n")
	var page GemtextPage
	for _, line := range lines {
		l, err := ParseLine(line, preformatted)
		page = append(page, l)
		if err != nil {
			return GemtextPage{}, err
		}
		if l.Type == PREFORMATTED_TOGGLE {
			preformatted = !preformatted
		}
	}
	return page, nil
}