/**
 * Turn a language-server spawn failure into an actionable message.
 *
 * A missing binary (spawn ENOENT) is the common, fixable case: the built-in
 * table assumes its servers are on PATH, and Claude Code LSP plugins ship
 * config only — never the binary (findings §18.3). The raw
 * "spawn pyright-langserver ENOENT" tells the user nothing about what to do,
 * so it is rewritten here with the install command when we know it, and with
 * PATH/plugin guidance when we don't. Every other failure passes through
 * unchanged. Enrichment happens once, where the failure is recorded, so the
 * one-time warning, /lsp, and the lsp_diagnostics tool all show the same text.
 */

/** Install commands for the built-in table's servers (and their npm siblings). */
export const INSTALL_HINTS: Record<string, string> = {
	"typescript-language-server": "npm install -g typescript-language-server typescript",
	"pyright-langserver": "npm install -g pyright",
	gopls: "go install golang.org/x/tools/gopls@latest",
	"rust-analyzer": "rustup component add rust-analyzer",
	jdtls: "brew install jdtls",
};

/** True when the failure is a spawn ENOENT — the binary itself is absent. */
export function isMissingBinary(failure: string): boolean {
	return /\bENOENT\b/.test(failure);
}

/**
 * Rewrite a missing-binary failure into install guidance; return anything
 * else verbatim. `pluginName` is set when a plugin's config (not the built-in
 * table) named the command.
 */
export function describeStartFailure(rawFailure: string, command: string, pluginName?: string): string {
	if (!isMissingBinary(rawFailure)) return rawFailure;
	const from = pluginName ? ` (configured by the ${pluginName} plugin)` : "";
	const hint = INSTALL_HINTS[command];
	if (hint) return `${command} is not installed${from}. Install it with: ${hint}`;
	if (command.startsWith("/")) {
		return `${command} does not exist${from}. ${pluginName ? "Check the plugin's installation." : "Check the configured path."}`;
	}
	const docs = pluginName ? " (the plugin's documentation should say how)" : "";
	return `${command} is not installed${from}. Install it and make sure it is on your PATH${docs}.`;
}