/**
 * Declarative host config system.
 *
 * Each supported host (Claude, Codex, Factory, OpenCode, OpenClaw, etc.) is
 * defined as a typed HostConfig object in hosts/*.ts. This module provides
 * the interface, loader, and validator.
 *
 * Architecture:
 *   hosts/*.ts  →  hosts/index.ts  →  host-config.ts (this file)
 *        │                                    │
 *        └── typed configs ──────────────────→ consumed by gen-skill-docs.ts,
 *                                              setup (via host-config-export.ts),
 *                                              skill-check.ts, worktree.ts,
 *                                              platform-detect, uninstall
 */

import type { Model } from './models';
import { validateModel } from './models';

export type HostTier = 'full' | 'experimental' | 'instruction-only';
export const HOST_TIERS: readonly HostTier[] = ['full', 'experimental', 'instruction-only'];

export interface HostCapabilities {
  /** Runs shell commands, so bin/ helpers and preambles execute. */
  toolExecution: boolean;
  /** 'native': a structured question tool; 'prose': questions are plain text. */
  questions: 'native' | 'prose';
  /** Has plan-mode transitions (enter/exit plan mode). */
  planMode: boolean;
  /** Can delegate work to sub-agents. */
  delegation: boolean;
  /** Can drive gstack's browser (needs toolExecution). */
  browser: boolean;
  /** 'enforced': hooks can block a tool call; 'advisory': safety skills only warn. */
  safetyHooks: 'enforced' | 'advisory';
}

export interface HostConfig {
  /** Unique host identifier (e.g., 'opencode'). Must match filename in hosts/. */
  name: string;
  /** Human-readable name for UI/logs (e.g., 'OpenCode'). */
  displayName: string;
  /** Binary name for `command -v` detection (e.g., 'opencode'). */
  cliCommand: string;
  /** Alternative binary names (e.g., ['droid'] for factory). */
  cliAliases?: string[];

  /** Model overlay used when generation does not receive an explicit --model. */
  defaultModel: Model;

  // --- Support Contract (docs/ADDING_A_HOST.md "Host tiers and capabilities") ---
  /**
   * full: installs, renders, and has a dated certification record (a real
   * workflow run plus an upgrade from an existing install).
   * experimental: installs and renders; not certified by a real run.
   * instruction-only: no install arm; setup prints instructions and changes nothing.
   */
  tier: HostTier;
  /** What the host runtime offers. Rendering and docs must not claim more. */
  capabilities: HostCapabilities;

  // --- Path Configuration ---
  /** Global install path relative to $HOME (e.g., '.config/opencode/skills/gstack'). */
  globalRoot: string;
  /** Project-local skill path relative to repo root (e.g., '.opencode/skills/gstack'). */
  localSkillRoot: string;
  /** Gitignored directory under repo root for generated docs (e.g., '.opencode'). */
  hostSubdir: string;
  /** Whether preamble generates $GSTACK_ROOT env vars (true for non-Claude hosts). */
  usesEnvVars: boolean;

  // --- Frontmatter Transformation ---
  frontmatter: {
    /** 'allowlist': ONLY keepFields survive. 'denylist': strip listed fields. */
    mode: 'allowlist' | 'denylist';
    /** Fields to preserve (allowlist mode only). */
    keepFields?: string[];
    /** Fields to remove (denylist mode only). */
    stripFields?: string[];
    /** Max chars for description field. null = no limit. */
    descriptionLimit?: number | null;
    /** What to do when description exceeds limit. Default: 'error'. */
    descriptionLimitBehavior?: 'error' | 'truncate' | 'warn';
    /** Additional frontmatter fields to inject (host-wide). */
    extraFields?: Record<string, unknown>;
    /**
     * Write the installed directory name (gstack-<skill>) into `name:`. For
     * hosts that index and de-duplicate skills by frontmatter name, where a
     * bare `review` would be shadowed by any other `review` skill (#2825).
     */
    nameMatchesDirectory?: boolean;
    /** Rename fields from template (e.g., { 'voice-triggers': 'triggers' }). */
    renameFields?: Record<string, string>;
    /** Conditionally add fields based on template frontmatter values. */
    conditionalFields?: Array<{ if: Record<string, unknown>; add: Record<string, unknown> }>;
  };

  // --- Generation ---
  generation: {
    /** Whether to create a metadata file alongside skills (always openai.yaml; gen-skill-docs hardcodes the format and reads the template's `codex_default_prompt:` key for its default_prompt). */
    generateMetadata: boolean;
    /** Skill directories to exclude from generation for this host. */
    skipSkills?: string[];
    /** Skill directories to include (allowlist). Union logic: include minus skip. */
    includeSkills?: string[];
  };

  // --- Content Rewrites ---
  /** Literal string replacements on generated SKILL.md content. Order matters, replaceAll. */
  pathRewrites: Array<{ from: string; to: string }>;
  /** Tool name string replacements on content. */
  toolRewrites?: Record<string, string>;
  /** Resolver functions that return empty string for this host. */
  suppressedResolvers?: string[];

  // --- Runtime Root ---
  runtimeRoot: {
    /** Explicit asset list for global install symlinks (no globs). */
    globalSymlinks: string[];
    /** Dir → explicit file list for selective file linking. */
    globalFiles?: Record<string, string[]>;
  };
  // --- Install Behavior ---
  install: {
    /** How skills are linked into the host dir. */
    linkingStrategy: 'real-dir-symlink' | 'symlink-generated';
    /**
     * 'harness': setup's arm for this host is `gstack-harness register <host>`
     * (lib/harness-register.ts): the host's render copied into the harness's own
     * skills folder with an ownership ledger, not linked into a host skills dir.
     */
    registration?: 'harness';
  };

  // --- Host-Specific Behavioral Config ---
  /** Git co-author trailer string. */
  coAuthorTrailer?: string;
  /** Learnings implementation: 'full' = cross-project, 'basic' = simple. */
  learningsMode?: 'full' | 'basic';
  /** Anti-prompt-injection boundary instruction for cross-model invocations. */
  boundaryInstruction?: string;

  // --- Session transcripts ---
  /**
   * Where this host keeps its own chat transcripts on disk, read by
   * /context-restore's no-checkpoint fallback (sections/transcripts.md).
   * `root` is the path pattern shown to the user; `layout` says how the
   * current workspace's files are told apart from another project's. Absent:
   * the host declares no transcript store, and the skill says so and falls
   * back to the shared record and git.
   */
  transcripts?: { root: string; layout: string };
}

// --- Validation ---

const NAME_REGEX = /^[a-z][a-z0-9-]*$/;
const PATH_REGEX = /^[a-zA-Z0-9_.\/${}~-]+$/;
const CLI_REGEX = /^[a-z][a-z0-9_-]*$/;

export function validateHostConfig(config: HostConfig, validResolverNames?: ReadonlySet<string>): string[] {
  const errors: string[] = [];

  if (!NAME_REGEX.test(config.name)) {
    errors.push(`name '${config.name}' must be lowercase alphanumeric with hyphens`);
  }
  if (!config.displayName) {
    errors.push('displayName is required');
  }
  if (!CLI_REGEX.test(config.cliCommand)) {
    errors.push(`cliCommand '${config.cliCommand}' contains invalid characters`);
  }
  if (config.cliAliases) {
    for (const alias of config.cliAliases) {
      if (!CLI_REGEX.test(alias)) {
        errors.push(`cliAlias '${alias}' contains invalid characters`);
      }
    }
  }
  if (!HOST_TIERS.includes(config.tier)) {
    errors.push(`tier '${config.tier}' must be one of ${HOST_TIERS.join(', ')}`);
  }
  const caps = config.capabilities;
  if (!caps) {
    errors.push('capabilities are required');
  } else {
    if (caps.browser && !caps.toolExecution) errors.push('capabilities.browser requires toolExecution');
    if (!['native', 'prose'].includes(caps.questions)) errors.push(`capabilities.questions must be 'native' or 'prose'`);
    if (!['enforced', 'advisory'].includes(caps.safetyHooks)) errors.push(`capabilities.safetyHooks must be 'enforced' or 'advisory'`);
  }
  if (config.install.registration === 'harness' && config.tier !== 'experimental') {
    errors.push('install.registration harness needs tier experimental (setup registers it through gstack-harness)');
  }
  const modelError = validateModel(config.defaultModel);
  if (modelError) {
    errors.push(`defaultModel ${modelError}`);
  }
  if (!PATH_REGEX.test(config.globalRoot)) {
    errors.push(`globalRoot '${config.globalRoot}' contains invalid characters`);
  }
  if (!PATH_REGEX.test(config.localSkillRoot)) {
    errors.push(`localSkillRoot '${config.localSkillRoot}' contains invalid characters`);
  }
  if (!PATH_REGEX.test(config.hostSubdir)) {
    errors.push(`hostSubdir '${config.hostSubdir}' contains invalid characters`);
  }
  if (!['allowlist', 'denylist'].includes(config.frontmatter.mode)) {
    errors.push(`frontmatter.mode must be 'allowlist' or 'denylist'`);
  }
  if (!['real-dir-symlink', 'symlink-generated'].includes(config.install.linkingStrategy)) {
    errors.push(`install.linkingStrategy must be 'real-dir-symlink' or 'symlink-generated'`);
  }

  // Cross-check suppressedResolvers against the known resolver names (injected to avoid a
  // circular import on the resolver registry). A typo would otherwise silently no-op: the
  // generator short-circuits suppressed names before the "unknown placeholder" throw, so an
  // unknown entry never surfaces at generation time either.
  if (validResolverNames && config.suppressedResolvers) {
    for (const name of config.suppressedResolvers) {
      if (!validResolverNames.has(name)) {
        errors.push(`suppressedResolvers entry '${name}' is not a known resolver`);
      }
    }
  }

  return errors;
}

export function validateAllConfigs(configs: HostConfig[], validResolverNames?: ReadonlySet<string>): string[] {
  const errors: string[] = [];

  // Per-config validation
  for (const config of configs) {
    const configErrors = validateHostConfig(config, validResolverNames);
    errors.push(...configErrors.map(e => `[${config.name}] ${e}`));
  }

  // Cross-config uniqueness checks
  const hostSubdirs = new Map<string, string>();
  const globalRoots = new Map<string, string>();
  const names = new Map<string, string>();

  for (const config of configs) {
    if (names.has(config.name)) {
      errors.push(`Duplicate name '${config.name}' (also used by ${names.get(config.name)})`);
    }
    names.set(config.name, config.name);

    if (hostSubdirs.has(config.hostSubdir)) {
      errors.push(`Duplicate hostSubdir '${config.hostSubdir}' (${config.name} and ${hostSubdirs.get(config.hostSubdir)})`);
    }
    hostSubdirs.set(config.hostSubdir, config.name);

    if (globalRoots.has(config.globalRoot)) {
      errors.push(`Duplicate globalRoot '${config.globalRoot}' (${config.name} and ${globalRoots.get(config.globalRoot)})`);
    }
    globalRoots.set(config.globalRoot, config.name);
  }

  return errors;
}