/**
 * Host adapter — pure answer assembly (spec §10; no PI runtime, no fs, no network).
 *
 * The shared typed core both render paths feed. A renderer captures a {@link RawSelection} per question
 * (widget-shaped); {@link assembleAnswers} turns the batch into the structured answers object keyed by
 * `question.key` (dotted for nested sections), which the engine then maps back onto the target schema.
 *
 * The only PI reference here is a *type* — the run mode for the capability gate — a type-only import,
 * fully erased at runtime, so this module stays offline-testable.
 */
import type { ExtensionContext } from "@earendil-works/pi-coding-agent"
import type { Question, Questionnaire, QuestionOption } from "../flow/questionnaire.ts"

/** PI run mode (`"tui" | "rpc" | "json" | "print"`), derived from the exported context type. */
export type ExtensionMode = ExtensionContext["mode"]

/** Sentinel option value meaning "the user took the implicit Other choice and typed free text". */
export const OTHER_VALUE = "__other__"

/** Display label for the implicit "Other" choice appended to a single-choice question. */
export const OTHER_LABEL = "Other…"

/**
 * A renderer's raw capture for one question, before typing. Both render paths (the rich `ctx.ui.custom`
 * form and the native-dialog fallback) produce this shape; {@link assembleAnswers} types it.
 */
export interface RawSelection {
	/** single: the picked option value, or {@link OTHER_VALUE} when the implicit "Other" choice was taken. */
	readonly option?: string
	/** multi: the picked option values. */
	readonly options?: readonly string[]
	/** text/chat: the entered string; also the free text when `option === OTHER_VALUE`. */
	readonly text?: string
}

/**
 * Assemble structured answers keyed by `question.key` from a renderer's raw per-question selections
 * (pure). single → the chosen value, or the "Other" free text; multi → an array; text/chat → a string.
 * A question with no capture collapses to the empty value of its shape (`""` / `[]`).
 */
export function assembleAnswers(
	questionnaire: Questionnaire,
	raw: Readonly<Record<string, RawSelection>>,
): Record<string, unknown> {
	const answers: Record<string, unknown> = {}
	for (const question of questionnaire.questions) {
		answers[question.key] = assembleOne(question, raw[question.key] ?? {})
	}
	return answers
}

function assembleOne(question: Question, selection: RawSelection): unknown {
	switch (question.kind) {
		case "single":
			return selection.option === OTHER_VALUE ? (selection.text ?? "") : (selection.option ?? "")
		case "multi":
			return [...(selection.options ?? [])]
		case "text":
		case "chat":
			return selection.text ?? ""
	}
}

/** A question's options ordered for display: recommended first (stable), original order otherwise. */
export function orderedOptions(question: Question): QuestionOption[] {
	return [...(question.options ?? [])].sort((a, b) => optionRank(b) - optionRank(a))
}

function optionRank(option: QuestionOption): number {
	return option.recommended ? 1 : 0
}

/** A question's prompt title: `"<section> — <question>"` when the question belongs to a section. */
export function questionTitle(question: Question): string {
	return question.section ? `${question.section} — ${question.question}` : question.question
}

/** A single option's display label: `label` + `(recommended)` marker + ` — description` when present. */
export function optionLabel(option: QuestionOption): string {
	const recommended = option.recommended ? " (recommended)" : ""
	const description = option.description ? ` — ${option.description}` : ""
	return `${option.label}${recommended}${description}`
}

/**
 * Capability gate (pure): render the rich `ctx.ui.custom` form only when a real terminal TUI is present.
 * Everything else (RPC / JSON / print) falls back to native per-question dialogs — which also work over
 * RPC, where `custom` cannot render.
 */
export function useRichForm(mode: ExtensionMode, hasUI: boolean): boolean {
	return hasUI && mode === "tui"
}