package mark

import (
	"bufio"
	"bytes"
	"fmt"
	"regexp"
	"strings"

	"github.com/reconquest/pkg/log"
)

const (
	HeaderParent     = `Parent`
	HeaderSpace      = `Space`
	HeaderType       = `Type`
	HeaderTitle      = `Title`
	HeaderLayout     = `Layout`
	HeaderAttachment = `Attachment`
	HeaderLabel      = `Label`
	HeaderInclude    = `Include`
)

type Meta struct {
	Parents     []string
	Space       string
	Type        string
	Title       string
	Layout      string
	Attachments map[string]string
	Labels      []string
}

var (
	reHeaderPatternV1 = regexp.MustCompile(`\[\]:\s*#\s*\(([^:]+):\s*(.*)\)`)
	reHeaderPatternV2 = regexp.MustCompile(`<!--\s*([^:]+):\s*(.*)\s*-->`)
)

func ExtractMeta(data []byte) (*Meta, []byte, error) {
	var (
		meta   *Meta
		offset int
	)

	scanner := bufio.NewScanner(bytes.NewBuffer(data))
	for scanner.Scan() {
		line := scanner.Text()

		if err := scanner.Err(); err != nil {
			return nil, nil, err
		}

		offset += len(line) + 1

		matches := reHeaderPatternV2.FindStringSubmatch(line)
		if matches == nil {
			matches = reHeaderPatternV1.FindStringSubmatch(line)
			if matches == nil {
				break
			}

			log.Warningf(
				fmt.Errorf(`legacy header usage found: %s`, line),
				"please use new header format: <!-- %s: %s -->",
				matches[1],
				matches[2],
			)
		}

		if meta == nil {
			meta = &Meta{}
			meta.Type = "page" //Default if not specified
			meta.Attachments = make(map[string]string)
		}

		header := strings.Title(matches[1])

		var value string
		if len(matches) > 1 {
			value = strings.TrimSpace(matches[2])
		}

		switch header {
		case HeaderParent:
			meta.Parents = append(meta.Parents, value)

		case HeaderSpace:
			meta.Space = strings.TrimSpace(value)

		case HeaderType:
			meta.Type = strings.TrimSpace(value)

		case HeaderTitle:
			meta.Title = strings.TrimSpace(value)

		case HeaderLayout:
			meta.Layout = strings.TrimSpace(value)

		case HeaderAttachment:
			meta.Attachments[value] = value

		case HeaderLabel:
			meta.Labels = append(meta.Labels, value)

		case HeaderInclude:
			// Includes are parsed by a different func
			continue

		default:
			log.Errorf(
				nil,
				`encountered unknown header %q line: %#v`,
				header,
				line,
			)

			continue
		}
	}

	if meta == nil {
		return nil, data, nil
	}

	if meta.Space == "" {
		return nil, nil, fmt.Errorf(
			"space key is not set (%s header is not set)",
			HeaderSpace,
		)
	}

	if meta.Title == "" {
		return nil, nil, fmt.Errorf(
			"page title is not set (%s header is not set)",
			HeaderTitle,
		)
	}

	return meta, data[offset:], nil
}