package tokenengine

import (
	"sort"
	"strings"

	"github.com/urpi/go-bananas/internal/domain"
)

// ResolvedTheme is the JSON payload served to runtime consumers. It carries
// both a flat variable map (what a browser or a design tool wants) and the
// nested resolved document (what an application that maps tokens onto component
// props wants), so consumers never have to choose.
type ResolvedTheme struct {
	Theme    ThemeRef          `json:"theme"`
	Tokens   domain.TokenDoc   `json:"tokens"`
	Variable map[string]string `json:"variables"`
	Meta     domain.ThemeMeta  `json:"meta,omitempty"`
}

// ThemeRef is the identity block repeated in every runtime payload.
type ThemeRef struct {
	Slug              string            `json:"slug"`
	Name              string            `json:"name"`
	Description       string            `json:"description,omitempty"`
	Version           int64             `json:"version"`
	Appearance        domain.Appearance `json:"appearance"`
	DefaultAppearance domain.Appearance `json:"defaultAppearance"`
	UpdatedAt         string            `json:"updatedAt"`
}

// JSONPayload builds the runtime JSON payload for one appearance.
func JSONPayload(theme *domain.Theme, appearance domain.Appearance) ResolvedTheme {
	if appearance == "" {
		appearance = theme.DefaultAppearance
	}
	doc := Resolve(theme, appearance)
	return ResolvedTheme{
		Theme: ThemeRef{
			Slug:              theme.Slug,
			Name:              theme.Name,
			Description:       theme.Description,
			Version:           theme.Version,
			Appearance:        appearance,
			DefaultAppearance: theme.DefaultAppearance,
			UpdatedAt:         theme.UpdatedAt.UTC().Format(domain.TimeFormat),
		},
		Tokens:   resolvedDocument(doc),
		Variable: doc.Variables(),
		Meta:     theme.Meta,
	}
}

// resolvedDocument renders the resolved tokens back into nested form, keeping
// the DTCG `$type`/`$value` shape so that the output can be fed straight into
// any DTCG-aware tool.
func resolvedDocument(doc *Doc) domain.TokenDoc {
	out := make(domain.TokenDoc, len(Groups)+1)
	for _, t := range doc.Tokens {
		insertResolved(out, strings.Split(t.Path, "."), t)
	}
	return out
}

// insertResolved places a token into the nested output document, creating the
// intermediate group objects on the way down.
func insertResolved(root domain.TokenDoc, segments []string, t FlatToken) {
	current := root
	for _, seg := range segments[:len(segments)-1] {
		child, ok := current[seg].(map[string]any)
		if !ok {
			child = map[string]any{}
			current[seg] = child
		}
		// Re-widen so that the next iteration can index it as a TokenDoc.
		current = child
	}
	leaf := map[string]any{ValueKey: t.Value, TypeKey: string(t.Kind)}
	if t.Description != "" {
		leaf[DescKey] = t.Description
	}
	current[segments[len(segments)-1]] = leaf
}

// ExportDocument produces a portable, self-describing token document for a
// theme. Unlike the runtime payload it keeps the appearance overrides intact,
// because the point of an export is that it can be re-imported losslessly.
func ExportDocument(theme *domain.Theme) domain.TokenDoc {
	out := domain.TokenDoc{SchemaKey: SchemaID}
	merged := make(domain.TokenDoc, len(theme.Tokens)+1)
	for k, v := range theme.Tokens {
		merged[k] = v
	}
	if _, ok := merged[SchemaKey]; !ok {
		out[SchemaKey] = SchemaID
	}
	delete(merged, SchemaKey)
	for k, v := range merged {
		out[k] = v
	}
	return out
}

// ManifestEntry describes one theme in the runtime manifest: the small payload
// a loader needs in order to build a theme picker without fetching every theme.
type ManifestEntry struct {
	Slug              string            `json:"slug"`
	Name              string            `json:"name"`
	Description       string            `json:"description,omitempty"`
	DefaultAppearance domain.Appearance `json:"defaultAppearance"`
	Version           int64             `json:"version"`
	Tags              []string          `json:"tags,omitempty"`
	CSS               string            `json:"css"`
	Tokens            string            `json:"tokens"`
}

// Manifest is the discovery document served from the runtime API.
type Manifest struct {
	// APIVersion is the runtime contract version. Consumers should refuse to
	// load a manifest whose major version they do not understand.
	APIVersion string `json:"apiVersion"`
	// Default is the slug applied when a consumer does not choose.
	Default string `json:"default,omitempty"`
	// BaseURL is the absolute runtime base the entries are relative to.
	BaseURL string            `json:"baseUrl"`
	Themes  []ManifestEntry   `json:"themes"`
	Extra   map[string]string `json:"extra,omitempty"`
}

// RuntimeAPIVersion is the current runtime contract version.
const RuntimeAPIVersion = "1"

// Tags extracts theme tags from the opaque meta block. Tags are the one piece
// of meta the engine understands, because the manifest needs them.
func Tags(meta domain.ThemeMeta) []string {
	raw, ok := meta["tags"]
	if !ok {
		return nil
	}
	switch t := raw.(type) {
	case []string:
		return t
	case []any:
		out := make([]string, 0, len(t))
		for _, v := range t {
			if s, ok := v.(string); ok && strings.TrimSpace(s) != "" {
				out = append(out, strings.TrimSpace(s))
			}
		}
		sort.Strings(out)
		return out
	case string:
		parts := strings.Split(t, ",")
		out := make([]string, 0, len(parts))
		for _, p := range parts {
			if s := strings.TrimSpace(p); s != "" {
				out = append(out, s)
			}
		}
		sort.Strings(out)
		return out
	default:
		return nil
	}
}