package classes

import (
	"context"
	"fmt"
	"net/url"
	"strings"

	"git.golem15.com/golem15/summercms/modules/backpack"
	"git.golem15.com/golem15/summercms/modules/pact"
)

// The elements of the SEO field types and widgets (assets/src/elements).
const (
	ElementText         = "golem15-seo-text"
	ElementRobots       = "golem15-seo-robots"
	ElementSERP         = "golem15-seo-serp"
	ElementImage        = "golem15-seo-image"
	ElementRobotsTxt    = "golem15-seo-robotstxt"
	ElementRobotsTester = "golem15-seo-robotstester"
)

// The element bundle every SEO field type loads.
var (
	elementScripts = []string{"assets/dist/seo.js"}
	elementStyles  = []string{"assets/dist/seo.css"}
)

// errRobotsInvalid is the refusal of a malformed robots value.
const errRobotsInvalid = "golem15.seo::lang.robots.invalid"

// errRobotsTooLarge refuses a robots.txt over MaxRobotsBytes.
const errRobotsTooLarge = "golem15.seo::lang.robots.too_large"

// FieldTypes returns the SEO admin field types:
//   - seotext and mlseotext (E1): text with a live length counter; option
//     measure: title (input) or description (textarea);
//   - seorobots and mlseorobots (E2): the robots directives editor; option
//     scope: record, rule or type; Decode refuses a malformed value;
//   - seoimage (E7): an uploaded social image stored in the media bucket,
//     its URL as the value (D-100); uploads need permission;
//   - robotstxt (E4): the robots.txt editor with live lint; Decode refuses
//     a file over 500 KB (D-22).
//
// app is asked for the booted application at request time.
func FieldTypes(app func() *backpack.App, permission string) []pact.FormFieldType {
	text := func(name string, translatable bool) pact.FormFieldType {
		return pact.FormFieldType{
			Name: name, Element: ElementText, Translatable: translatable,
			Scripts: elementScripts, Styles: elementStyles,
			Options: []string{"measure"}, CheckOptions: checkMeasure, Decode: decodeText,
		}
	}
	robots := func(name string, translatable bool) pact.FormFieldType {
		return pact.FormFieldType{
			Name: name, Element: ElementRobots, Translatable: translatable,
			Scripts: elementScripts, Styles: elementStyles,
			Options: []string{"scope"}, CheckOptions: checkScope, Decode: decodeRobots,
		}
	}
	return []pact.FormFieldType{
		text("seotext", false),
		text("mlseotext", true),
		robots("seorobots", false),
		robots("mlseorobots", true),
		{
			Name: "seoimage", Element: ElementImage,
			Scripts: elementScripts, Styles: elementStyles,
			Decode: decodeImage, Upload: UploadImage(app, permission),
		},
		{
			Name: "robotstxt", Element: ElementRobotsTxt,
			Scripts: elementScripts, Styles: elementStyles,
			Decode: decodeRobotsTxt,
		},
	}
}

// decodeRobotsTxt stores a robots.txt with Unix line ends and refuses one
// over MaxRobotsBytes (robots.too_large); lint findings are warnings in
// the element and never block a save.
func decodeRobotsTxt(_ context.Context, in pact.FormFieldValue) (pact.FormFieldDecoded, error) {
	s, ok := stringValue(in.Value)
	if !ok {
		return pact.FormFieldDecoded{}, &pact.FormFieldError{Messages: []string{"The " + in.Field + " field must be text."}}
	}
	s = strings.ReplaceAll(s, "\r\n", "\n")
	if len(s) > MaxRobotsBytes {
		return pact.FormFieldDecoded{}, &pact.FormFieldError{Messages: []string{errRobotsTooLarge}}
	}
	return pact.FormFieldDecoded{Value: s}, nil
}

func checkMeasure(options map[string]any) error {
	if raw, ok := options["measure"]; ok {
		if s, _ := raw.(string); s != "title" && s != "description" {
			return fmt.Errorf("measure must be title or description, got %v", raw)
		}
	}
	return nil
}

func checkScope(options map[string]any) error {
	if raw, ok := options["scope"]; ok {
		if s, _ := raw.(string); s != "record" && s != "rule" && s != "type" {
			return fmt.Errorf("scope must be record, rule or type, got %v", raw)
		}
	}
	return nil
}

// stringValue reads a submitted value as text; nil is "".
func stringValue(v any) (string, bool) {
	switch s := v.(type) {
	case nil:
		return "", true
	case string:
		return s, true
	}
	return "", false
}

func decodeText(_ context.Context, in pact.FormFieldValue) (pact.FormFieldDecoded, error) {
	s, ok := stringValue(in.Value)
	if !ok {
		return pact.FormFieldDecoded{}, &pact.FormFieldError{Messages: []string{"The " + in.Field + " field must be text."}}
	}
	return pact.FormFieldDecoded{Value: strings.TrimSpace(s)}, nil
}

// decodeRobots stores a robots value in the fixed order; a malformed value
// (reachable only through MCP or an import) is refused.
func decodeRobots(_ context.Context, in pact.FormFieldValue) (pact.FormFieldDecoded, error) {
	s, ok := stringValue(in.Value)
	if !ok {
		return pact.FormFieldDecoded{}, &pact.FormFieldError{Messages: []string{errRobotsInvalid}}
	}
	normal, err := NormalizeRobots(s)
	if err != nil {
		return pact.FormFieldDecoded{}, &pact.FormFieldError{Messages: []string{errRobotsInvalid}}
	}
	return pact.FormFieldDecoded{Value: normal}, nil
}

// decodeImage accepts an empty value, a path or an http(s) URL.
func decodeImage(_ context.Context, in pact.FormFieldValue) (pact.FormFieldDecoded, error) {
	s, ok := stringValue(in.Value)
	s = strings.TrimSpace(s)
	if !ok || !ValidImageURL(s) {
		return pact.FormFieldDecoded{}, &pact.FormFieldError{Messages: []string{errImageURL}}
	}
	return pact.FormFieldDecoded{Value: s}, nil
}

// ValidURLRef reports whether v is a path ("/x", not "//x") or an absolute
// http(s) URL with a host, without spaces or control characters.
func ValidURLRef(v string) bool {
	if v == "" || strings.ContainsFunc(v, func(r rune) bool { return r <= ' ' || r == 0x7f }) {
		return false
	}
	if strings.HasPrefix(v, "/") {
		return !strings.HasPrefix(v, "//")
	}
	u, err := url.Parse(v)
	return err == nil && (u.Scheme == "http" || u.Scheme == "https") && u.Host != ""
}