package com.megatim.manuel.core.theme;

import javafx.scene.Parent;

import java.io.IOException;
import java.io.InputStream;
import java.io.UncheckedIOException;
import java.net.URL;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

/**
 * Charte graphique du manuel : couleurs du viewer JavaFX, identité (titre, logo),
 * feuilles de style additionnelles et variables des pages HTML générées.
 *
 * <p>Immuable ; se construit via {@link #builder()} (pré-rempli avec les valeurs par
 * défaut, charte Sirius-FT) ou {@link #defaultTheme()}.</p>
 *
 * <p>Mécanique côté viewer : la CSS embarquée déclare des <em>looked-up colors</em>
 * ({@code -mgt-accent}, {@code -mgt-button}, ...) sur la classe {@code .help-viewer}
 * et les référence partout ; {@link #applyTo(Parent)} injecte les valeurs du thème
 * via {@code setStyle} puis attache les feuilles de style. Une application hôte peut
 * donc changer la charte sans fournir de CSS, ou surcharger finement via
 * {@code extraViewerStylesheets} (les {@code styleClass} du viewer sont un contrat
 * stable : {@code help-viewer}, {@code button-primary}, {@code help-left-panel},
 * {@code help-project-title}, {@code help-status}, ...).</p>
 *
 * <p>Mécanique côté pages HTML : {@link #renderHtmlStyles()} rend le template
 * {@code styles.css} (embarqué ou fourni via {@code htmlStylesTemplate}) en
 * substituant les variables {@code ${html.*}} (surchargeables une à une via
 * {@code htmlVar(...)}).</p>
 */
public final class ManuelTheme {

    /** Feuille de style par défaut du viewer (looked-up colors), embarquée dans la lib. */
    public static final String DEFAULT_VIEWER_CSS =
            "/com/megatim/manuel/core/viewer/help-viewer.css";
    /** Template par défaut du styles.css des pages HTML générées. */
    public static final String DEFAULT_HTML_TEMPLATE =
            "/com/megatim/manuel/core/theme/html-styles-template.css";

    // --- Couleurs viewer (défauts = charte Sirius) ---
    private final String accentColor;
    private final String buttonColor;
    private final String buttonBorderColor;
    private final String panelBorderColor;
    private final String selectionColor;
    private final String hoverColor;
    private final String textColor;
    private final String backgroundColor;

    // --- Identité ---
    private final String appTitle;
    private final URL logo;

    // --- CSS viewer ---
    private final String viewerStylesheet;
    private final List<String> extraViewerStylesheets;

    // --- CSS HTML ---
    private final String htmlStylesTemplate;
    private final Map<String, String> htmlVars;

    private ManuelTheme(Builder b) {
        this.accentColor = b.accentColor;
        this.buttonColor = b.buttonColor;
        this.buttonBorderColor = b.buttonBorderColor;
        this.panelBorderColor = b.panelBorderColor;
        this.selectionColor = b.selectionColor;
        this.hoverColor = b.hoverColor;
        this.textColor = b.textColor;
        this.backgroundColor = b.backgroundColor;
        this.appTitle = b.appTitle;
        this.logo = b.logo;
        this.viewerStylesheet = b.viewerStylesheet;
        this.extraViewerStylesheets = Collections.unmodifiableList(new ArrayList<>(b.extraViewerStylesheets));
        this.htmlStylesTemplate = b.htmlStylesTemplate;
        this.htmlVars = Collections.unmodifiableMap(new LinkedHashMap<>(b.htmlVars));
    }

    /** Thème par défaut : charte Sirius-FT. */
    public static ManuelTheme defaultTheme() {
        return builder().build();
    }

    /** Builder pré-rempli avec les valeurs par défaut (charte Sirius-FT). */
    public static Builder builder() {
        return new Builder();
    }

    /**
     * Applique le thème à la racine du viewer : injection des looked-up colors puis
     * attachement de la CSS par défaut (ou de remplacement) et des surcharges.
     */
    public void applyTo(Parent root) {
        root.setStyle("-mgt-accent: " + accentColor + ";"
                + " -mgt-button: " + buttonColor + ";"
                + " -mgt-button-border: " + buttonBorderColor + ";"
                + " -mgt-panel-border: " + panelBorderColor + ";"
                + " -mgt-selection: " + selectionColor + ";"
                + " -mgt-hover: " + hoverColor + ";"
                + " -mgt-text: " + textColor + ";"
                + " -mgt-bg: " + backgroundColor + ";");
        if (viewerStylesheet != null) {
            root.getStylesheets().add(viewerStylesheet);
        } else {
            URL css = ManuelTheme.class.getResource(DEFAULT_VIEWER_CSS);
            if (css != null) {
                root.getStylesheets().add(css.toExternalForm());
            }
        }
        root.getStylesheets().addAll(extraViewerStylesheets);
    }

    /** Rend le contenu du styles.css des pages HTML (template + variables du thème). */
    public String renderHtmlStyles() {
        String template = htmlStylesTemplate != null ? htmlStylesTemplate : loadDefaultHtmlTemplate();
        Map<String, String> vars = defaultHtmlVars();
        vars.putAll(htmlVars);
        String out = template;
        for (Map.Entry<String, String> e : vars.entrySet()) {
            out = out.replace("${" + e.getKey() + "}", e.getValue());
        }
        return out;
    }

    /** Variables HTML par défaut (charte Sirius) ; base de la substitution du template. */
    public static Map<String, String> defaultHtmlVars() {
        Map<String, String> v = new LinkedHashMap<>();
        v.put("html.font", "'Segoe UI',Tahoma,Arial,sans-serif");
        v.put("html.text", "#1a1a1a");
        v.put("html.bg", "#ffffff");
        // Charte Sirius-FT : anthracite/violet, aucun bleu
        v.put("html.h1", "#3d4d5c");
        v.put("html.h2", "#5d4a75");
        v.put("html.h3", "#756784");
        v.put("html.link", "#756784");
        v.put("html.caption", "#444444");
        v.put("html.muted", "#555555");
        v.put("html.rule", "#d0d0d0");
        v.put("html.navbar.bg", "#f1edf5");
        v.put("html.navbar.border", "#d5cbdf");
        v.put("html.navbar.disabled", "#a8b0ba");
        v.put("html.table.border", "#b0b8c4");
        v.put("html.img.border", "#c0c0c0");
        return v;
    }

    private static String loadDefaultHtmlTemplate() {
        try (InputStream in = ManuelTheme.class.getResourceAsStream(DEFAULT_HTML_TEMPLATE)) {
            if (in == null) {
                throw new IOException("Resource introuvable : " + DEFAULT_HTML_TEMPLATE);
            }
            return new String(in.readAllBytes(), StandardCharsets.UTF_8);
        } catch (IOException e) {
            throw new UncheckedIOException(e);
        }
    }

    public String getAccentColor() { return accentColor; }
    public String getButtonColor() { return buttonColor; }
    public String getButtonBorderColor() { return buttonBorderColor; }
    public String getPanelBorderColor() { return panelBorderColor; }
    public String getSelectionColor() { return selectionColor; }
    public String getHoverColor() { return hoverColor; }
    public String getTextColor() { return textColor; }
    public String getBackgroundColor() { return backgroundColor; }
    public String getAppTitle() { return appTitle; }
    public URL getLogo() { return logo; }
    public String getViewerStylesheet() { return viewerStylesheet; }
    public List<String> getExtraViewerStylesheets() { return extraViewerStylesheets; }
    public String getHtmlStylesTemplate() { return htmlStylesTemplate; }
    public Map<String, String> getHtmlVars() { return htmlVars; }

    /** Builder mutable ; toutes les valeurs sont pré-remplies charte Sirius. */
    public static final class Builder {
        private String accentColor = "#e9e4ef";
        private String buttonColor = "#f0f0f0";
        private String buttonBorderColor = "#bac0c0";
        private String panelBorderColor = "#d1d1d1";
        private String selectionColor = "#D6ECDB";
        private String hoverColor = "#f0f6f2";
        private String textColor = "#323232";
        private String backgroundColor = "#ffffff";
        private String appTitle;
        private URL logo;
        private String viewerStylesheet;
        private final List<String> extraViewerStylesheets = new ArrayList<>();
        private String htmlStylesTemplate;
        private final Map<String, String> htmlVars = new LinkedHashMap<>();

        public Builder accentColor(String v) { this.accentColor = v; return this; }
        public Builder buttonColor(String v) { this.buttonColor = v; return this; }
        public Builder buttonBorderColor(String v) { this.buttonBorderColor = v; return this; }
        public Builder panelBorderColor(String v) { this.panelBorderColor = v; return this; }
        public Builder selectionColor(String v) { this.selectionColor = v; return this; }
        public Builder hoverColor(String v) { this.hoverColor = v; return this; }
        public Builder textColor(String v) { this.textColor = v; return this; }
        public Builder backgroundColor(String v) { this.backgroundColor = v; return this; }
        public Builder appTitle(String v) { this.appTitle = v; return this; }
        public Builder logo(URL v) { this.logo = v; return this; }
        /** Remplace entièrement la CSS embarquée du viewer (URI de feuille de style). */
        public Builder viewerStylesheet(String uri) { this.viewerStylesheet = uri; return this; }
        /** Ajoute une CSS de surcharge, chargée après la CSS par défaut. */
        public Builder extraViewerStylesheet(String uri) { this.extraViewerStylesheets.add(uri); return this; }
        /** Remplace entièrement le template styles.css des pages HTML. */
        public Builder htmlStylesTemplate(String template) { this.htmlStylesTemplate = template; return this; }
        /** Surcharge une variable du template HTML (ex. {@code html.h1}, {@code html.link}). */
        public Builder htmlVar(String key, String value) { this.htmlVars.put(key, value); return this; }

        public ManuelTheme build() {
            return new ManuelTheme(this);
        }
    }
}