import * as vscode from 'vscode';
import { HAClient, HAEntity } from './haClient';

// ──────────────────────────────────────────────────────────────────────────────
//  Completion Provider
// ──────────────────────────────────────────────────────────────────────────────

export class EntityCompletionProvider implements vscode.CompletionItemProvider {
    private cachedDomains: Set<string> = new Set();

    constructor(private haClient: HAClient) {
        this.rebuildDomainCache();
        haClient.onEntitiesUpdated(() => this.rebuildDomainCache());
    }

    private rebuildDomainCache() {
        this.cachedDomains = new Set(this.haClient.getDomains());
    }

    provideCompletionItems(
        document: vscode.TextDocument,
        position: vscode.Position,
        _token: vscode.CancellationToken,
        context: vscode.CompletionContext
    ): vscode.CompletionList | undefined {
        const entities = this.haClient.getEntities();
        if (entities.length === 0) {
            return undefined;
        }

        const lineText = document.lineAt(position).text;
        const textBefore = lineText.substring(0, position.character);

        // ── Case 1: "domain.partial" — user typed a dot after a domain name ──
        const dotMatch = textBefore.match(/\b([a-z][a-z_]*)\.([a-z0-9_]*)$/);
        if (dotMatch) {
            const domain = dotMatch[1];
            const partial = dotMatch[2];
            if (this.cachedDomains.has(domain)) {
                // Range covers "domain.partial" so the full entity_id replaces it
                const replaceStart = position.translate(0, -(domain.length + 1 + partial.length));
                const replaceRange = new vscode.Range(replaceStart, position);
                const items = this.buildDomainItems(entities, domain, partial, replaceRange);
                if (items.length > 0) {
                    return new vscode.CompletionList(items, false);
                }
            }
        }

        // ── Case 2: Trigger was "." but domain is unknown — skip ─────────────
        if (context.triggerKind === vscode.CompletionTriggerKind.TriggerCharacter &&
            context.triggerCharacter === '.') {
            return undefined;
        }

        // ── Case 3: YAML value context — broad entity search ─────────────────
        if (document.languageId === 'yaml') {
            const valueMatch = textBefore.match(/(?::\s+|:\s*['"]|[-]\s+|[-]\s*['"])([a-z][a-z0-9_.]*)?$/);
            if (valueMatch) {
                const partial = valueMatch[1] || '';
                return new vscode.CompletionList(
                    this.buildAllItems(entities, partial),
                    partial.length < 3
                );
            }
        }

        // ── Case 4: Python string context — inside quotes ────────────────────
        if (document.languageId === 'python') {
            const stringMatch = textBefore.match(/['"]([a-z][a-z0-9_.]*)$/);
            if (stringMatch) {
                const partial = stringMatch[1];
                return new vscode.CompletionList(
                    this.buildAllItems(entities, partial),
                    partial.length < 3
                );
            }
        }

        return undefined;
    }

    private buildDomainItems(
        entities: HAEntity[],
        domain: string,
        partial: string,
        replaceRange: vscode.Range
    ): vscode.CompletionItem[] {
        const items: vscode.CompletionItem[] = [];
        const prefix = `${domain}.`;

        for (const entity of entities) {
            if (!entity.entity_id.startsWith(prefix)) {
                continue;
            }
            if (partial && !entity.entity_id.substring(prefix.length).includes(partial)) {
                continue;
            }

            const item = new vscode.CompletionItem(
                entity.entity_id,
                vscode.CompletionItemKind.Value
            );

            const friendly = entity.attributes?.friendly_name as string | undefined;
            item.detail = friendly
                ? `${friendly} — ${entity.state}`
                : entity.state;
            item.documentation = new vscode.MarkdownString(formatEntityMarkdown(entity));
            item.filterText = entity.entity_id;
            item.sortText = entity.entity_id;
            item.range = replaceRange;
            items.push(item);
        }
        return items;
    }

    private buildAllItems(entities: HAEntity[], partial: string): vscode.CompletionItem[] {
        const items: vscode.CompletionItem[] = [];
        const lowerPartial = partial.toLowerCase();

        for (const entity of entities) {
            if (lowerPartial && !entity.entity_id.includes(lowerPartial)) {
                const friendly = (entity.attributes?.friendly_name as string || '').toLowerCase();
                if (!friendly.includes(lowerPartial)) {
                    continue;
                }
            }

            const item = new vscode.CompletionItem(
                entity.entity_id,
                vscode.CompletionItemKind.Value
            );

            const friendly = entity.attributes?.friendly_name as string | undefined;
            item.detail = friendly
                ? `${friendly} — ${entity.state}`
                : entity.state;
            item.documentation = new vscode.MarkdownString(formatEntityMarkdown(entity));
            item.filterText = entity.entity_id;
            item.sortText = entity.entity_id;
            items.push(item);
        }
        return items;
    }
}

// ──────────────────────────────────────────────────────────────────────────────
//  Hover Provider
// ──────────────────────────────────────────────────────────────────────────────

const ENTITY_ID_PATTERN = /[a-z][a-z_]*\.[a-z0-9][a-z0-9_]*/;

export class EntityHoverProvider implements vscode.HoverProvider {
    constructor(private haClient: HAClient) {}

    provideHover(
        document: vscode.TextDocument,
        position: vscode.Position
    ): vscode.Hover | undefined {
        const range = document.getWordRangeAtPosition(position, ENTITY_ID_PATTERN);
        if (!range) {
            return undefined;
        }

        const word = document.getText(range);
        const entity = this.haClient.getEntity(word);
        if (!entity) {
            return undefined;
        }

        const md = new vscode.MarkdownString();
        md.supportHtml = true;
        md.isTrusted = true;

        const friendly = entity.attributes?.friendly_name as string | undefined;
        md.appendMarkdown(`### ${friendly || entity.entity_id}\n\n`);
        md.appendMarkdown(`| | |\n|---|---|\n`);
        md.appendMarkdown(`| **Entity** | \`${entity.entity_id}\` |\n`);
        md.appendMarkdown(`| **State** | **\`${entity.state}\`** |\n`);

        if (entity.attributes) {
            const skip = new Set(['friendly_name', 'icon', 'entity_picture', 'supported_features', 'supported_color_modes']);
            const attrs = Object.entries(entity.attributes)
                .filter(([k]) => !skip.has(k))
                .slice(0, 12);

            for (const [key, value] of attrs) {
                const display = typeof value === 'object' ? JSON.stringify(value) : String(value);
                const truncated = display.length > 60 ? display.substring(0, 57) + '...' : display;
                const safeKey = key.replace(/\|/g, '\\|');
                const safeVal = truncated.replace(/\|/g, '\\|');
                md.appendMarkdown(`| ${safeKey} | \`${safeVal}\` |\n`);
            }
        }

        md.appendMarkdown(`\n*Last changed: ${entity.last_changed}*`);

        return new vscode.Hover(md, range);
    }
}

// ──────────────────────────────────────────────────────────────────────────────
//  Helpers
// ──────────────────────────────────────────────────────────────────────────────

function formatEntityMarkdown(entity: HAEntity): string {
    const lines: string[] = [];
    const friendly = entity.attributes?.friendly_name as string | undefined;
    lines.push(`**${friendly || entity.entity_id}**\n`);
    lines.push(`- **State:** \`${entity.state}\``);
    lines.push(`- **Entity ID:** \`${entity.entity_id}\``);

    if (entity.attributes) {
        const skip = new Set(['friendly_name', 'icon', 'entity_picture']);
        const attrs = Object.entries(entity.attributes)
            .filter(([k]) => !skip.has(k))
            .slice(0, 8);

        if (attrs.length > 0) {
            lines.push('\n**Attributes:**');
            for (const [key, value] of attrs) {
                const val = typeof value === 'object' ? JSON.stringify(value) : String(value);
                lines.push(`- ${key}: \`${val}\``);
            }
        }
    }

    lines.push(`\n*Last changed: ${entity.last_changed}*`);
    return lines.join('\n');
}