package cabana

import (
	"fmt"
	"io/fs"
	"regexp"
	"strings"

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

// widgetTagPattern is a valid custom-element name restricted to lowercase
// ASCII: a letter, then at least one hyphenated segment.
var widgetTagPattern = regexp.MustCompile(`^[a-z][a-z0-9]*(-[a-z0-9]+)+$`)

// reservedWidgetTags are the hyphenated names the HTML specification reserves;
// customElements.define refuses them.
var reservedWidgetTags = map[string]bool{
	"annotation-xml": true, "color-profile": true, "font-face": true, "font-face-src": true,
	"font-face-uri": true, "font-face-format": true, "font-face-name": true, "missing-glyph": true,
}

// builtinToolbarActions are the toolbar actions the framework implements
// itself (D-14); a controller may not register an action with these names.
var builtinToolbarActions = map[string]bool{"create": true, "delete": true}

// widgetTagPrefix is the custom-element prefix a plugin's widgets must use:
// the plugin ID lowercased with dots and underscores turned into hyphens,
// plus a trailing hyphen (acme.conform -> "acme-conform-"). It keeps two
// plugins from defining the same element.
func widgetTagPrefix(pluginID string) string {
	return strings.NewReplacer(".", "-", "_", "-").Replace(strings.ToLower(pluginID)) + "-"
}

// compileExtension validates a controller's runtime admin extension points
// after its list and form are compiled and its writable fields are bound: the
// registered actions and every `type: widget` field. Every failure stops boot.
func compileExtension(pluginID string, cc *CompiledController, fsys fs.FS) error {
	if cc == nil || cc.Controller == nil {
		return nil
	}
	id := cc.Controller.ID()
	actions, err := compileActions(cc.Controller)
	if err != nil {
		return fmt.Errorf("cabana: admin controller %s/%s: %w", pluginID, id, err)
	}
	cc.Actions = actions
	if cc.Form == nil {
		return nil
	}
	file := cc.Form.fieldsPath
	if file == "" {
		file = "fields.yaml"
	}
	fields := map[string]FormField{}
	for _, field := range cc.Form.Fields {
		fields[field.Name] = field
	}
	writable := map[string]bool{}
	for _, field := range cc.Writable {
		writable[field.Name] = true
	}
	prefix := widgetTagPrefix(pluginID)
	for i := range cc.Form.Fields {
		field := &cc.Form.Fields[i]
		if field.Type != "widget" {
			continue
		}
		if err := checkWidgetTag(field.Widget, prefix); err != nil {
			return bootErr(pluginID, id, file, fmt.Errorf("field %s: %w", field.Name, err))
		}
		action, ok := actions[field.Action]
		if !ok {
			return bootErr(pluginID, id, file, fmt.Errorf("field %s: action %s is not registered by the controller (pact.HasAdminActions)", field.Name, field.Action))
		}
		for _, key := range field.Fill {
			target, exists := fields[key]
			if !exists {
				return bootErr(pluginID, id, file, fmt.Errorf("field %s: fill %s is not a field of this form", field.Name, key))
			}
			if !scalarFormField(target.Type) || !writable[key] {
				return bootErr(pluginID, id, file, fmt.Errorf("field %s: fill %s is not a writable scalar field", field.Name, key))
			}
		}
		field.ActionLabel = action.Label
	}
	return nil
}

func checkWidgetTag(tag, prefix string) error {
	if !widgetTagPattern.MatchString(tag) {
		return fmt.Errorf("widget %q is not a valid custom-element name (lowercase, with a hyphen)", tag)
	}
	if reservedWidgetTags[tag] {
		return fmt.Errorf("widget %q is a reserved element name", tag)
	}
	if !strings.HasPrefix(tag, prefix) {
		return fmt.Errorf("widget %q must start with the plugin prefix %q", tag, prefix)
	}
	return nil
}

// compileActions collects a controller's registered actions into the single
// action namespace (assumption-delta decision: create and delete are reserved).
func compileActions(ctl pact.AdminController) (map[string]pact.AdminAction, error) {
	out := map[string]pact.AdminAction{}
	src, ok := ctl.(pact.HasAdminActions)
	if !ok || src == nil {
		return out, nil
	}
	for _, action := range src.AdminActions() {
		if !identifier(action.Name) {
			return nil, fmt.Errorf("action name %q is not an identifier", action.Name)
		}
		if builtinToolbarActions[action.Name] {
			return nil, fmt.Errorf("action %s uses a reserved built-in name (create, delete)", action.Name)
		}
		if _, dup := out[action.Name]; dup {
			return nil, fmt.Errorf("duplicate action %s", action.Name)
		}
		if action.Run == nil {
			return nil, fmt.Errorf("action %s has no Run function", action.Name)
		}
		out[action.Name] = action
	}
	return out, nil
}