// SPDX-License-Identifier: MPL-2.0

// Package cms supplies bounded classification and editorial relationship values.
// It does not define content types, layouts, authorization, or commerce policy.
// Applications own those decisions and publish exact immutable revisions.
package cms

import (
	"errors"
	"regexp"
	"strings"
	"unicode"
	"unicode/utf8"
)

var (
	ErrInvalid  = errors.New("cms: invalid value")
	ErrConflict = errors.New("cms: revision or slug conflict")
	ErrNotFound = errors.New("cms: not found")
	identifier  = regexp.MustCompile(`^[A-Za-z0-9][A-Za-z0-9_.:-]{0,127}$`)
	slug        = regexp.MustCompile(`^[a-z0-9]+(?:-[a-z0-9]+)*$`)
	kind        = regexp.MustCompile(`^[a-z][a-z0-9-]{0,39}$`)
)

const MaxTerms = 24
const MaxLinks = 16

// Reference names an application-owned resource, never a mutable URL or title.
type Reference struct {
	Kind string `json:"kind"`
	ID   string `json:"id"`
}

func ValidID(value string) bool   { return identifier.MatchString(value) }
func ValidSlug(value string) bool { return len(value) <= 80 && slug.MatchString(value) }
func ValidText(value string, max int) bool {
	return utf8.ValidString(value) && len(value) <= max && strings.TrimSpace(value) == value && !strings.ContainsFunc(value, unicode.IsControl)
}
func (r Reference) Validate() error {
	if !kind.MatchString(r.Kind) || !ValidID(r.ID) {
		return ErrInvalid
	}
	return nil
}

// Associations are an immutable revision's term memberships and explicit links.
// Reverse discovery reads the same links; callers must not store a second edge.
// Terms and Links are independently optional. The zero value is valid for a
// valid source; unclassified content never needs a placeholder taxonomy or link.
type Associations struct {
	Terms []string    `json:"terms,omitempty"`
	Links []Reference `json:"links,omitempty"`
}

func (a Associations) Validate(source Reference) error {
	if source.Validate() != nil || len(a.Terms) > MaxTerms || len(a.Links) > MaxLinks {
		return ErrInvalid
	}
	terms := map[string]bool{}
	for _, id := range a.Terms {
		if !ValidID(id) || terms[id] {
			return ErrInvalid
		}
		terms[id] = true
	}
	links := map[Reference]bool{}
	for _, ref := range a.Links {
		if ref.Validate() != nil || ref == source || links[ref] {
			return ErrInvalid
		}
		links[ref] = true
	}
	return nil
}

// Taxonomy is an editor-named vocabulary, not a database-defined content type.
// Slug is fixed after creation; Name/Description and availability may change.
type Taxonomy struct {
	ID          string `json:"id"`
	Slug        string `json:"slug"`
	Name        string `json:"name"`
	Description string `json:"description,omitempty"`
	Revision    int64  `json:"revision"`
	Active      bool   `json:"active"`
}

func (v Taxonomy) Validate() error {
	if !ValidID(v.ID) || !ValidSlug(v.Slug) || v.Name == "" || !ValidText(v.Name, 120) || !ValidText(v.Description, 500) || v.Revision < 1 {
		return ErrInvalid
	}
	return nil
}

// Term identity survives renaming and retirement. Retirement hides discovery;
// it does not rewrite old associations or imply removal of related resources.
type Term struct {
	ID          string `json:"id"`
	TaxonomyID  string `json:"taxonomy_id"`
	Slug        string `json:"slug"`
	Name        string `json:"name"`
	Description string `json:"description,omitempty"`
	Revision    int64  `json:"revision"`
	Active      bool   `json:"active"`
}

func (v Term) Validate() error {
	if !ValidID(v.ID) || !ValidID(v.TaxonomyID) || !ValidSlug(v.Slug) || v.Name == "" || !ValidText(v.Name, 120) || !ValidText(v.Description, 500) || v.Revision < 1 {
		return ErrInvalid
	}
	return nil
}

type ResourceVersion struct {
	Reference
	Revision int64 `json:"revision"`
}
type Page struct {
	Items []ResourceVersion `json:"items"`
	Next  *Reference        `json:"next,omitempty"`
}