/**
 * Direct GitLab TemplateIR → `.gitlab-ci.yml` text emission.
 *
 * We deliberately bypass the existing `gitlabSerializer.serialize()` because
 * that path consumes `Map<string, Declarable>` (entity instances built by
 * user TS code), not a raw IR. Going through entity instances would require
 * runtime construction of typed objects we don't have. Direct emission is
 * ~60 LOC.
 */

import type { TemplateIR } from "@intentius/chant/import/parser";
import { emitYAML } from "@intentius/chant/yaml";

const RESERVED_TOP_LEVEL_ORDER = [
  "spec",
  "include",
  "default",
  "stages",
  "variables",
  "workflow",
  "image",
  "services",
  "before_script",
  "after_script",
  "cache",
  "pages",
];

function isReservedTopLevelKey(key: string): boolean {
  return RESERVED_TOP_LEVEL_ORDER.includes(key);
}

function emitKeyValue(key: string, value: unknown, indent: number): string {
  const prefix = "  ".repeat(indent);
  if (value === null || value === undefined) return `${prefix}${key}: null`;
  if (typeof value === "boolean" || typeof value === "number") return `${prefix}${key}: ${value}`;
  if (typeof value === "string") return `${prefix}${key}: ${emitYAML(value, indent + 1)}`;
  if (Array.isArray(value)) {
    if (value.length === 0) return `${prefix}${key}: []`;
    return `${prefix}${key}:${emitYAML(value, indent + 1)}`;
  }
  if (typeof value === "object") {
    if (Object.keys(value).length === 0) return `${prefix}${key}: {}`;
    return `${prefix}${key}:${emitYAML(value, indent + 1)}`;
  }
  return `${prefix}${key}: ${String(value)}`;
}

function emitBlock(obj: Record<string, unknown>, indent: number): string {
  return Object.entries(obj)
    .filter(([, v]) => v !== undefined)
    .map(([k, v]) => emitKeyValue(k, v, indent))
    .join("\n");
}

/**
 * Convert a GitLab `TemplateIR` (produced by the GH→GL transformer) into
 * `.gitlab-ci.yml` text.
 */
export function emitGitlabYaml(ir: TemplateIR): string {
  const top: Record<string, unknown> = {};

  // Stages from metadata
  const meta = (ir.metadata ?? {}) as Record<string, unknown>;
  if (Array.isArray(meta.stages) && meta.stages.length > 0) {
    top.stages = meta.stages;
  }

  // Top-level variables from metadata.variables
  if (meta.variables && typeof meta.variables === "object" && Object.keys(meta.variables).length > 0) {
    top.variables = meta.variables;
  }

  // Workflow / Default / Include resources go into reserved top-level keys
  for (const r of ir.resources) {
    if (r.type === "GitLab::CI::Workflow") {
      top.workflow = r.properties;
    } else if (r.type === "GitLab::CI::Default") {
      top.default = r.properties;
    } else if (r.type === "GitLab::CI::Include") {
      top.include = r.properties;
    }
  }

  // Job resources go at the top level keyed by logicalId (kebab-cased)
  const jobs: Record<string, unknown> = {};
  for (const r of ir.resources) {
    if (r.type === "GitLab::CI::Job") {
      const key = (r.metadata?.originalName as string) ?? r.logicalId;
      if (isReservedTopLevelKey(key)) {
        // Avoid colliding with reserved keywords; prefix
        jobs[`job-${key}`] = r.properties;
      } else {
        jobs[key] = r.properties;
      }
    }
  }

  // Emit ordered top-level keys (reserved first, then jobs)
  const lines: string[] = [];

  for (const key of RESERVED_TOP_LEVEL_ORDER) {
    if (top[key] !== undefined) {
      lines.push(emitKeyValue(key, top[key], 0));
    }
  }

  // Migration banner comment
  if (meta.migration && typeof meta.migration === "object") {
    const m = meta.migration as Record<string, unknown>;
    if (lines.length === 0) {
      lines.push(`# Generated by chant migrate from ${m.sourceFile ?? "(unknown)"}`);
      lines.push("");
    } else {
      lines.unshift("");
      lines.unshift(`# Generated by chant migrate from ${m.sourceFile ?? "(unknown)"}`);
    }
  }

  // Jobs (sorted by logicalId for determinism)
  const jobKeys = Object.keys(jobs).sort();
  for (const key of jobKeys) {
    lines.push("");
    lines.push(emitKeyValue(key, jobs[key], 0));
  }

  return lines.join("\n") + "\n";
}