/**
 * Investigation Overview synthesis seam — standalone domain function.
 *
 * Purpose: produce a structurally distinct two-part overview that keeps
 *   (A) evidence-backed understanding and
 *   (B) remaining plausible interpretations
 * epistemically separate.
 *
 * Input contract:
 *   { situationGraph, findings, plausibleInterpretations }
 *
 * Output contract:
 *   {
 *     "understanding":              "evidence-backed synthesis",
 *     "plausibleInterpretations":  "qualified synthesis of remaining interpretations"
 *   }
 *
 * Does NOT produce: recommendation, decision, confidence score, next action, priority, readiness.
 */

import { z } from "zod";
import { getProvider } from "../llm/provider.js";
import { filterEligibleFindings } from "./current-understanding-synthesis.js";

export { filterEligibleFindings };

// ── Overview-specific output validation schema ────────────────

const overviewResponseSchema = z.object({
  understanding: z.string().min(1),
  plausibleInterpretations: z.string().min(1),
});

const FORBIDDEN_FIELD_NAMES = new Set([
  "recommendation",
  "decision",
  "confidenceScore",
  "nextAction",
  "priority",
  "readiness",
]);

/**
 * Validate that the raw overview response has exactly two semantic fields:
 * - understanding (string)
 * - plausibleInterpretations (string)
 * and no decision/recommendation/priority/readiness/next-action leakage.
 */
export function validateOverviewResponse(raw) {
  if (raw == null) {
    return { valid: false, reason: "Provider returned null/undefined" };
  }

  let parsed;
  if (typeof raw === "string") {
    try {
      parsed = JSON.parse(raw);
    } catch {
      return { valid: false, reason: "Provider output is not valid JSON" };
    }
  } else if (typeof raw === "object") {
    parsed = raw;
  } else {
    return { valid: false, reason: "Provider output has unexpected type" };
  }

  // Reject any forbidden epistemic fields
  for (const key of Object.keys(parsed)) {
    if (FORBIDDEN_FIELD_NAMES.has(key)) {
      return { valid: false, reason: `forbidden_field: ${key}` };
    }
  }

  const result = overviewResponseSchema.safeParse(parsed);
  if (!result.success) {
    return { valid: false, reason: "Missing or invalid required fields" };
  }

  return { valid: true, data: result.data };
}

// ── Overview-specific prompt construction ─────────────────────

const KNOWN_SUPPORTED_STATUSES = new Set(["known", "supported"]);

function safeDesc(value) {
  return (value && typeof value === "string") ? value : null;
}

/**
 * Build the overview synthesis prompt from SituationGraph, eligible Findings,
 * and plausible interpretations.
 *
 * Produces three evidence sections:
 *   1. Evidence-backed understanding inputs (known + supported nodes + eligible Findings)
 *   2. Plausible interpretations inputs (kept separate from evidence)
 *   3. Epistemic boundary rules
 */
export function buildOverviewSynthesisPrompt(situationGraph, findings, plausibleInterpretations) {
  // Evidence-backed projection: reuse the existing known+supported logic
  const knownNodes = (situationGraph.nodes ?? [])
    .filter((n) => KNOWN_SUPPORTED_STATUSES.has(n.status))
    .filter((n) => n.status === "known")
    .map((n) => ({
      kind: n.kind ?? null,
      label: safeDesc(n.label),
      description: safeDesc(n.description),
      value: n.value ?? null,
      unit: n.unit ?? null,
      status: n.status ?? null,
    }));

  const supportedNodes = (situationGraph.nodes ?? [])
    .filter((n) => KNOWN_SUPPORTED_STATUSES.has(n.status))
    .filter((n) => n.status !== "known")
    .map((n) => ({
      kind: n.kind ?? null,
      label: safeDesc(n.label),
      description: safeDesc(n.description),
      value: n.value ?? null,
      unit: n.unit ?? null,
      status: n.status ?? null,
    }));

  const centralStatement = safeDesc(situationGraph.centralStatement) || "";

  // Eligible Findings (reuse existing filter)
  const eligibleFindings = filterEligibleFindings(findings);
  const agreedFindings = eligibleFindings.filter((f) => f.userDisposition === "agree");
  const workingFindings = eligibleFindings.filter((f) => f.userDisposition === null);

  // Format nodes for prompt display
  function formatNodes(nodes, title) {
    if (!nodes || nodes.length === 0) return "";
    return nodes.map(
      (n) => `  ${title}: kind=${n.kind}, label="${n.label}", value=${n.value ? n.value + (n.unit ? " (" + n.unit + ")" : "") : null} — ${n.description ?? "(no description)"} [${n.status}]`
    ).join("\n");
  }

  const knownSection = formatNodes(knownNodes, "Known");
  const supportedSection = formatNodes(supportedNodes, "Supported");

  // Format plausible interpretations (kept separate from evidence)
  const interpSections = [];
  if (plausibleInterpretations && Array.isArray(plausibleInterpretations)) {
    for (const interp of plausibleInterpretations) {
      interpSections.push({
        id: interp.id ?? null,
        description: safeDesc(interp.description) || "Unlabelled interpretation",
        confidence: interp.confidence ?? "unknown",
        supportingEvidenceIds: interp.supportingEvidenceIds ?? [],
      });
    }
  }

  const findingsSections = [];
  if (agreedFindings.length > 0) {
    findingsSections.push({
      label: "Confirmed Evidence",
      items: agreedFindings.map((f) => ({ proposition: f.proposition, id: f.id ?? null })),
    });
  }
  if (workingFindings.length > 0) {
    findingsSections.push({
      label: "Working Premises",
      items: workingFindings.map((f) => ({ proposition: f.proposition, id: f.id ?? null })),
    });
  }

  const prompt = `You are producing an investigation overview with two structurally distinct sections.

Situation Framing:
${centralStatement ? "  Central Statement: " + centralStatement : "(none)"}

=== SECTION A INPUTS — Evidence-Backed Understanding ===

Provider-Active Evidence:
Known Facts:${knownSection || " (none)"}
Supported Inferences:${supportedSection || " (none)"}

Eligible Findings:
${findingsSections.length > 0 ? JSON.stringify(findingsSections, null, 2) : "(none)"}

=== SECTION B INPUTS — Plausible Interpretations (NOT evidence-backed) ===

Plausible Interpretations:
${interpSections.length > 0 ? JSON.stringify(interpSections, null, 2) : "(none)"}

=== EPISTEMIC BOUNDARY RULES ===

1. Section A (understanding) MUST contain only established or supported understanding from the evidence in SECTION A INPUTS above.
2. Section A MUST NOT include open questions, unresolved uncertainties, assumptions, provisional hypotheses, speculative explanations, or future investigation needs.
3. Plausible interpretations from SECTION B INPUTS MUST remain explicitly qualified as interpretations — never promoted into Section A (understanding).
4. Plausible interpretations must not be presented as established evidence or confirmed facts.
5. Produce exactly ONE coherent narrative paragraph for "understanding" from SECTION A inputs only.
6. Produce exactly ONE coherent narrative paragraph for "plausibleInterpretations" from SECTION B inputs only. Each interpretation should be clearly qualified as an interpretation.
7. Do NOT introduce any new facts not present in the supplied evidence.
8. Return ONLY a JSON object with this exact structure:
   {"understanding": "...", "plausibleInterpretations": "..."}
9. Neither field may contain recommendations, decisions, confidence scores, next actions, priorities, or readiness assessments.
10. This is a FRESH synthesis — do NOT treat any previous overview or Current Understanding as input.

Both fields must be non-empty strings.`;

  return prompt;
}

// ── Overview domain function ──────────────────────────────────

/**
 * Synthesize an investigation overview with structurally distinct sections:
 *   - understanding: evidence-backed synthesis
 *   - plausibleInterpretations: qualified remaining interpretations
 *
 * @param {{ situationGraph, findings, plausibleInterpretations }} params
 * @param {{ provider, modelName }} deps
 * @returns {Promise<{ understanding: string, plausibleInterpretations: string }>}
 */
export async function synthesizeInvestigationOverview(params, deps) {
  const { situationGraph, findings = [], plausibleInterpretations = [] } = params;

  if (!situationGraph || typeof situationGraph !== "object") {
    throw new Error("situationGraph is required");
  }
  if (!Array.isArray(findings)) {
    throw new Error("findings must be an array");
  }
  if (!Array.isArray(plausibleInterpretations)) {
    throw new Error("plausibleInterpretations must be an array");
  }

  // Provider acquisition (reuse existing pattern)
  const provider = deps?.provider ?? getProvider();
  const modelName = deps?.modelName ?? process.env.OLLAMA_MODEL;

  if (!provider || typeof provider.generateReconstruction !== "function") {
    throw new Error("Invalid dependency: provider must have generateReconstruction");
  }

  // Build overview-specific prompt (keeps evidence/interpretation separate)
  const prompt = buildOverviewSynthesisPrompt(situationGraph, findings, plausibleInterpretations);

  let rawResponse;
  try {
    rawResponse = await provider.generateReconstruction(
      prompt,
      modelName,
    );
  } catch (err) {
    throw new Error(`Overview synthesis provider call failed: ${err.message}`);
  }

  // Validate against overview-specific contract
  const validated = validateOverviewResponse(rawResponse);
  if (!validated.valid) {
    throw new Error(`Overview synthesis validation failed: ${validated.reason}`);
  }

  return validated.data;
}