// ── Algorithm-tab block definitions ────────────────────────────────────────
//
// Blocks that live on the Algorithm (flowchart) canvas:
//   WCStart, WCEnd, WCOutput, WCDecision, WCAssign, WCExpression, WCVarRef
//
// Each extends WCBlock (from wcblock.js) and provides generateOwnCode().
//
// Load order dependencies:
//   wcblock.js  → WCBlock base class
//   helpers.js  → findDataSource, resolveSourceName, escapeString, toCName,
//                 commentPrefix, refreshVarRefOptions
//   dom.js      → $id
//   error.js    → showError


// ── WCStart — program entry point ──────────────────────────────────────────

/** Program entry point. Cannot be deleted. */
class WCStart extends WCBlock {
  delete() { showError("Cannot delete the start block."); }
}


// ── WCEnd — program exit ───────────────────────────────────────────────────

/** Program exit block with errno autocomplete. At least one must return 0. */
class WCEnd extends WCBlock {
  connectedCallback() {
    super.connectedCallback();
    this._errnoItems = _ERRNO_ITEMS;
    this._selectedCode = 0;
    this._el.input = this._require(".end-errno-input");
    this._el.suggestions = this._require(".end-errno-suggestions");
    this._el.desc = this._require(".end-desc-text");

    this._el.input.addEventListener("input", () => this._onInput());
    this._el.input.addEventListener("focus", () => { if (this._el.suggestions.children.length > 0) this._showSuggestions(); });
    this._el.input.addEventListener("keydown", ev => this._onKeyDown(ev));
    this._el.suggestions.addEventListener("mousedown", ev => {
      const sug = ev.target.closest(".end-errno-suggestion");
      if (sug) {
        const code = parseInt(sug.dataset.code);
        if (!isNaN(code)) this._selectByCode(code);
      }
    });
    document.addEventListener("click", ev => {
      if (!this.contains(ev.target)) this._hideSuggestions();
    });

    this._el.input.value = "0";
    this._selectByCode(0);
  }

  _onInput() {
    const q = this._el.input.value.trim().toLowerCase();
    if (!q) {
      this._renderSuggestions(this._errnoItems);
      this._showSuggestions();
      return;
    }
    const qCode = parseInt(q);
    const matches = this._errnoItems.filter(item =>
      (!isNaN(qCode) && item.code === qCode) ||
      item.name.toLowerCase().includes(q) ||
      item.desc.toLowerCase().includes(q)
    );
    this._renderSuggestions(matches);
    this._showSuggestions();
  }

  _renderSuggestions(items) {
    this._el.suggestions.innerHTML = "";
    for (const item of items) this._addSuggestion(item);
  }

  _addSuggestion(item) {
    const div = document.createElement("div");
    div.className = "end-errno-suggestion";
    div.dataset.code = item.code;
    const codeSpan = document.createElement("span");
    codeSpan.className = "end-suggestion-code";
    codeSpan.textContent = item.code + "  " + item.name;
    div.appendChild(codeSpan);
    const descSpan = document.createElement("span");
    descSpan.className = "end-suggestion-desc";
    descSpan.textContent = item.desc;
    div.appendChild(descSpan);
    this._el.suggestions.appendChild(div);
  }

  _showSuggestions() { this._el.suggestions.style.display = "block"; }
  _hideSuggestions() { this._el.suggestions.style.display = "none"; }

  _onKeyDown(ev) {
    if (ev.key === "ArrowDown" || ev.key === "ArrowUp") {
      ev.preventDefault();
      const items = [...this._el.suggestions.querySelectorAll(".end-errno-suggestion")];
      let idx = items.findIndex(el => el.classList.contains("highlighted"));
      if (ev.key === "ArrowDown") idx = Math.min(idx + 1, items.length - 1);
      else idx = Math.max(idx - 1, 0);
      items.forEach(el => el.classList.remove("highlighted"));
      if (items[idx]) {
        items[idx].classList.add("highlighted");
        items[idx].scrollIntoView({ block: "nearest" });
      }
    }
    if (ev.key === "Enter") {
      const hl = this._el.suggestions.querySelector(".highlighted");
      if (hl) {
        ev.preventDefault();
        this._selectByCode(parseInt(hl.dataset.code));
      }
    }
    if (ev.key === "Escape") this._hideSuggestions();
  }

  _selectByCode(code) {
    this._selectedCode = code;
    const item = this._errnoItems.find(i => i.code === code);
    if (item) {
      const display = code + "  " + item.name;
      this._el.input.value = display;
      this._el.input.setAttribute("value", display);
      this._el.desc.textContent = item.desc;
      this.dataset.exitError = code !== 0 ? "true" : "";
    } else {
      const display = code + "  error";
      this._el.input.value = display;
      this._el.input.setAttribute("value", display);
      this._el.desc.textContent = "unknown error";
      this.dataset.exitError = "true";
    }
    this._hideSuggestions();
  }

  _enforceZeroEnd() {
    if (this._selectedCode === 0) return;
    const others = document.querySelectorAll("wc-end");
    for (const other of others) {
      if (other !== this && other._selectedCode === 0) return;
    }
    this._selectByCode(0);
  }

  _hasOtherZero() {
    const others = document.querySelectorAll("wc-end");
    for (const other of others) {
      if (other !== this && other._selectedCode === 0) return true;
    }
    return false;
  }

  delete() {
    if (this.id === "main-end") { showError("Cannot delete the default end block."); return; }
    if (!this._hasOtherZero()) { showError("At least one end block must return 0."); return; }
    super.delete();
    setTimeout(() => {
      for (const end of document.querySelectorAll("wc-end")) end._enforceZeroEnd();
    }, 0);
  }

  _genStringFrees() {
    const freed = new Set();
    let code = "";
    for (const el of document.querySelectorAll("#variable-area > [data-block]")) {
      if (el.dataType === "string") {
        const name = resolveSourceName(el);
        if (name && !freed.has(name)) {
          freed.add(name);
          code += `  free(${name}.data);\n`;
        }
      }
    }
    return code;
  }

  generateOwnCode() {
    const code = this._selectedCode;
    if (code === 0) {
      const frees = this._genStringFrees();
      if (frees) return `\n${frees}  return 0;\n`;
      return "\n  return 0;\n";
    }
    return `\n  exit(${code});\n`;
  }

  saveData() { return { exitCode: this._selectedCode }; }
  restoreData(d) {
    this._selectByCode(d.exitCode !== undefined ? d.exitCode : 0);
  }
}

function _buildErrnoItems() {
  const items = [
    { code: 0,   name: "success",       desc: "success" },
    { code: 255, name: "error",         desc: "generic error" },
  ];
  for (const e of ERRNO_LIST) {
    items.push({ code: e.code, name: e.name, desc: e.desc });
  }
  return items;
}
const _ERRNO_ITEMS = _buildErrnoItems();


// ── WCOutput — printf statement ────────────────────────────────────────────

/** Output description block. Provides inline documentation without generating code. */
class WCOutput extends WCBlock {
  connectedCallback() {
    super.connectedCallback();
    this._el.textarea = this.querySelector("textarea");
  }

  saveData() { return { textarea: this._el.textarea.value }; }
  restoreData(d) { this.querySelector("textarea").value = d.textarea || ""; }

  generateOwnCode() {
    const msg = escapeString(this._el.textarea.value || "");
    return `\nprintf("${msg}");\n`;
  }
}


// ── WCDecision — conditional branch ────────────────────────────────────────

/** Conditional branch block; splits flow into yes/no branches and emits if/else C code. */
class WCDecision extends WCBlock {
  connectedCallback() {
    super.connectedCallback();
    this._el.boolIn = this.querySelector(".decision-data-in");
  }

  _getBoolName(block) {
    return resolveSourceName(block) || "flag";
  }

  _branchDescendants(roots) {
    const d = new Set(), q = [...roots];
    for (const el of q) {
      if (d.has(el)) continue;
      d.add(el);
      if (el instanceof WCDecision) continue;
      for (const p of el.wcNextFlow) {
        if (!d.has(p.toElement)) q.push(p.toElement);
      }
    }
    return d;
  }

  _emitBranch(roots, stop, visited) {
    const v = new Set(visited);
    let c = "";
    const walk = el => {
      if (v.has(el) || stop.has(el)) return;
      v.add(el);
      if (el instanceof WCDecision) {
        c += el.generateCode(v);
      } else {
        c += el.generateOwnCode();
        for (const p of el.wcNextFlow) walk(p.toElement);
      }
    };
    for (const el of roots) walk(el);
    return c;
  }

  generateCode(visited = new Set()) {
    const yesTargets = [], noTargets = [];
    for (const path of this.wcNextFlow) {
      const hook = path.fromHook;
      if (!hook || hook.id === "hook-out1") {
        yesTargets.push(path.toElement);
      } else if (hook.id === "hook-out0") {
        noTargets.push(path.toElement);
      }
    }

    const yesAll = this._branchDescendants(yesTargets);
    const noAll  = this._branchDescendants(noTargets);
    const shared = new Set([...yesAll].filter(el => noAll.has(el) && el !== this));

    const yesCode = this._emitBranch(yesTargets, shared, visited);
    const noCode  = this._emitBranch(noTargets, shared, visited);
    const sharedCode = this._emitBranch([...shared], new Set(), visited);

    for (const el of yesAll) visited.add(el);
    for (const el of noAll)  visited.add(el);

    const source = findDataSource(this._el.boolIn);
    const cond = source ? this._getBoolName(source) : "0";
    let out = "";
    if (yesCode || noCode) {
      if (yesCode) out += `if (${cond}) {\n${yesCode}}`;
      if (noCode) {
        out += yesCode
          ? ` else {\n${noCode}}`
          : `if (!(${cond})) {\n${noCode}}`;
      }
    }
    out += sharedCode;
    return out ? `\n${out}\n` : "";
  }
}


// ── WCAssign — variable assignment block ───────────────────────────────────

/** Variable assignment block; writes to scalar/array/vector/string targets with data hooks. */
class WCAssign extends WCBlock {
  connectedCallback() {
    super.connectedCallback();
    this._el.target = this.querySelector(".assign-target");
    this._el.value = this.querySelector(".assign-value");
    this._el.dataIn = this.querySelector(".assign-row .hook");
    this._el.indexArea = this.querySelector(".assign-index-area");
    this._el.indexInput = this.querySelector(".assign-index");
    this._el.indexHook = this.querySelector(".assign-index-area .hook");

    this._el.target.addEventListener("change", () => this._syncType());
    setTimeout(() => {
      refreshVarRefOptions();
      this._syncType();
      this._updateValueVisibility();
    }, 0);
  }

  _updateValueVisibility() {
    const hasConn = findDataSource(this._el.dataIn) !== null;
    this._el.value.classList.toggle("hidden", hasConn);
    const hasIdxConn = findDataSource(this._el.indexHook) !== null;
    this._el.indexInput.classList.toggle("hidden", hasIdxConn);
  }

  _syncType() {
    const id = this._el.target.value;
    const target = id ? $id(id) : null;
    const type = target ? target.dataType : "scalar";
    this._el.dataIn.dataset.type = type;
    this._el.dataIn.title = "expects " + type;
    this._el.indexArea.style.display = type === "array" ? "flex" : "none";
  }

  _getSourceVarName(block) {
    return resolveSourceName(block) || "x";
  }

  _genStringLiteral(name, raw) {
    const escaped = escapeString(raw);
    const len = raw.length;
    return "\n" + [
      `free(${name}.data);`,
      `${name}.length = ${len};`,
      `${name}.data = malloc(${len} + 1);`,
      `memcpy(${name}.data, "${escaped}", ${len});`,
      `${name}.data[${len}] = 0;`,
    ].join("\n") + "\n";
  }

  _genStringCopy(dst, src) {
    return "\n" + [
      `free(${dst}.data);`,
      `${dst}.length = ${src}.length;`,
      `${dst}.data = malloc(${src}.length + 1);`,
      `memcpy(${dst}.data, ${src}.data, ${src}.length);`,
      `${dst}.data[${dst}.length] = 0;`,
    ].join("\n") + "\n";
  }

  saveData() { return { target: this._el.target.value, value: this._el.value.value, index: this._el.indexInput.value }; }
  restoreData(d) {
    const tgt = this.querySelector(".assign-target");
    tgt.dataset.restoredValue = d.target || "";
    tgt.value = d.target || "";
    this.querySelector(".assign-value").value = d.value || "";
    this.querySelector(".assign-index").value = d.index || "0";
    this._syncType();
    this._updateValueVisibility();
  }

  generateOwnCode() {
    const targetId = this._el.target.value;
    if (!targetId) return "";
    const target = $id(targetId);
    if (!target) return "";
    const targetName = resolveSourceName(target) || "x";
    const targetType = target.dataType || "scalar";

    const source = findDataSource(this._el.dataIn);

    if (targetType === "array") {
      const idxSource = findDataSource(this._el.indexHook);
      const idxExpr = idxSource ? this._getSourceVarName(idxSource) : (this._el.indexInput.value || "0");
      if (!source) {
        const raw = this._el.value.value || "0";
        return `\n${targetName}[${idxExpr}] = ${raw};\n`;
      }
      const srcName = this._getSourceVarName(source);
      return `\n${targetName}[${idxExpr}] = ${srcName};\n`;
    }

    if (!source) {
      const raw = this._el.value.value || "0";
      if (targetType === "string") return this._genStringLiteral(targetName, raw);
      return `\n${targetName} = ${raw};\n`;
    }

    const srcName = this._getSourceVarName(source);
    if (targetType === "string" && source.dataType === "string") {
      return this._genStringCopy(targetName, srcName);
    }
    return `\n${targetName} = ${srcName};\n`;
  }
}


// ── WCVarRef — read-only variable reference with data output hook ──────────

/** Read-only variable reference with data output hook; syncs type from selected variable. */
class WCVarRef extends WCBlock {
  connectedCallback() {
    super.connectedCallback();
    this._el.select = this.querySelector(".varref-select");
    this._el.select.addEventListener("change", () => {
      this._syncType();
    });
  }

  _syncType() {
    const id = this._el.select.value;
    const target = id ? $id(id) : null;
    const hook = this.querySelector(".hook-out");
    hook.dataset.type = target ? target.dataType : "scalar";
  }

  saveData() { return { selected: this._el.select.value }; }
  restoreData(d) {
    const sel = this.querySelector(".varref-select");
    sel.dataset.restoredValue = d.selected || "";
    sel.value = d.selected || "";
    const id = sel.value;
    const target = id ? $id(id) : null;
    const hook = this.querySelector(".hook-out");
    hook.dataset.type = target ? target.dataType : "scalar";
  }

  generateOwnCode() { return ""; }
}


// ── WCExpression — mathematical expression with MathJax rendering & data hooks ──

/** Math expression block with LaTeX rendering via MathJax and dynamic variable data hooks. */
class WCExpression extends WCBlock {
  get dataType() {
    const el = this._el?.latex || this.querySelector(".expr-latex");
    const latex = el?.value || "";
    return /[<>]|==|!=|\\(?:ge|le|ne|neq|geq|leq|land|lor|wedge|vee|neg|lnot)\b/.test(latex) ? "boolean" : "scalar";
  }

  connectedCallback() {
    super.connectedCallback();
    this._el.name = this.querySelector(".expr-name");
    this._el.latex = this.querySelector(".expr-latex");
    this._el.rendered = this.querySelector(".expr-rendered");
    this._el.varhooks = this.querySelector(".expr-varhooks");

    this._el.latex.addEventListener("input", () => this._renderFormula());
    setTimeout(() => this._renderFormula(), 0);
  }

  saveData() { return { name: this._el.name.value, latex: this._el.latex.value }; }
  restoreData(d) {
    this._el.name.value = d.name || "";
    this._el.latex.value = d.latex || "";
    this._renderFormula();
  }

  _parseVariables(latex) {
    const tokens = latex
      .replace(/\\[a-zA-Z]+/g, "")
      .replace(/[{}\[\]()]/g, " ")
      .replace(/[\d+*\/^_=,;:!?<>|~`@#\$%&'-]/g, " ")
      .split(/\s+/)
      .filter(t => t.length > 0 && t.length <= 8)
      .filter(t => ![
        "sin","cos","tan","cot","sec","csc","arcsin","arccos","arctan",
        "log","ln","lg","exp","sqrt","lim","inf","sum","int","prod","det",
        "gcd","lcm","max","min","arg","mod","Re","Im","deg","Pr","var",
        "alpha","beta","gamma","delta","epsilon","zeta","eta","theta",
        "iota","kappa","lambda","mu","nu","xi","omicron","rho","sigma",
        "tau","upsilon","phi","chi","psi","omega","varepsilon","vartheta",
        "varpi","varphi","varrho","varsigma","varUpsilon"
      ].includes(t.toLowerCase()));
    return [...new Set(tokens)];
  }

  _rebuildVarHooks(vars) {
    this._el.varhooks.innerHTML = "";
    for (const v of vars) {
      const hook = document.createElement("button");
      hook.className = "hook";
      hook.id = this.id + "-vh-" + v;
      hook.title = v;
      hook.textContent = v;
      hook.dataset.direction = "in";
      hook.dataset.linkType = "data";
      hook.dataset.type = "scalar";
      hook.dataset.exit = "left";
      this._setupHook(hook);
      this._el.varhooks.appendChild(hook);
    }
  }

  _renderFormula() {
    const latex = this._el.latex.value;
    const outHook = this.querySelector(".hook-out");
    if (outHook) outHook.dataset.type = this.dataType;
    this._el.rendered.innerHTML = "";
    const vars = latex.trim() ? this._parseVariables(latex) : [];
    this._rebuildVarHooks(vars);
    if (!latex.trim()) return;
    if (window.MathJax && MathJax.typesetPromise) {
      const wrapper = document.createElement("div");
      wrapper.textContent = "$$" + latex + "$$";
      const typeset = () => {
        MathJax.typesetPromise([wrapper]).then(() => {
          this._el.rendered.innerHTML = wrapper.innerHTML;
        }).catch(() => {
          this._el.rendered.textContent = "\u26A0 error";
        });
      };
      if (MathJax.startup && MathJax.startup.promise && MathJax.startup.promise.then) {
        MathJax.startup.promise.then(typeset);
      } else {
        typeset();
      }
    } else {
      this._el.rendered.textContent = latex;
    }
  }

  generateCode(visited = new Set()) {
    if (visited.has(this)) return "";
    visited.add(this);
    return this.generateOwnCode();
  }

  generateOwnCode() {
    const name = this._el.name.value || "res";
    const formula = this._el.latex.value || "0";
    const type = this.dataType === "boolean" ? "int" : "double";
    return `${type} ${name} = ${formula};`;
  }
}