#!/usr/bin/env python3
"""
i-GSM-style generator (mod 7) with ASCII variables.

Two operator modes:
  ascii  (hard): glyphs @ & $ ~ with MEANING randomized per problem
                 (may include lin / prodplus / modular inverse).
  arith  (easy): fixed conventional operators + - * / with fixed meanings:
                 a + b = (a + b) mod 7
                 a - b = (a - b) mod 7
                 a * b = (a × b) mod 7
                 a / b = (a × b⁻¹) mod 7   [b≠0]

Expressions are evaluated STRICTLY LEFT TO RIGHT (no standard precedence);
this convention is stated in each problem's preamble.

Usage:
    python construct.py --ops ascii --outdir out          # hard version
    python construct.py --ops arith --outdir out_arith    # easy +-*/ version
    python construct.py --ops arith --n 250 --depths 2 3 4 --distractors 0
"""

import argparse
import json
import os
import random

MOD = 7
INV7 = {1: 1, 2: 4, 3: 5, 4: 2, 5: 3, 6: 6}   # inverses mod 7 (0 excluded)

LETTERS_1 = "EFGHIJKL"    # first symbol of a variable name  (X in X#Y)
LETTERS_2 = "IJKLMNOP"    # second symbol of a variable name (Y in X#Y)


# --------------------------------------------------------------------------- #
# Operators
# --------------------------------------------------------------------------- #
def make_op(kind, glyph, rng=None, params=None):
    if kind == "add":
        f = lambda a, b: (a + b) % MOD
        definition = f"a {glyph} b = (a + b) mod {MOD}"
        show = lambda a, b: f"({a} + {b}) mod {MOD}"
        params = {}
    elif kind == "mul":
        f = lambda a, b: (a * b) % MOD
        definition = f"a {glyph} b = (a × b) mod {MOD}"
        show = lambda a, b: f"({a} × {b}) mod {MOD}"
        params = {}
    elif kind == "sub":
        f = lambda a, b: (a - b) % MOD
        definition = f"a {glyph} b = (a - b) mod {MOD}"
        show = lambda a, b: f"({a} - {b}) mod {MOD}"
        params = {}
    elif kind == "prodplus":
        f = lambda a, b: (a * b + a + b) % MOD
        definition = f"a {glyph} b = (a×b + a + b) mod {MOD}"
        show = lambda a, b: f"({a}×{b} + {a} + {b}) mod {MOD}"
        params = {}
    elif kind == "lin":
        if params is None:
            assert rng is not None
            params = {"al": rng.choice([2, 3, 4, 5]), "be": rng.choice([2, 3, 4, 5])}
        al, be = params["al"], params["be"]
        f = lambda a, b, al=al, be=be: (al * a + be * b) % MOD
        definition = f"a {glyph} b = ({al}·a + {be}·b) mod {MOD}"
        show = lambda a, b, al=al, be=be: f"({al}×{a} + {be}×{b}) mod {MOD}"
    elif kind == "div":
        f = lambda a, b: (a * INV7[b % MOD]) % MOD
        definition = f"a {glyph} b = (a × b⁻¹) mod {MOD}   [b≠0]"
        show = lambda a, b: f"({a} × {b}⁻¹) mod {MOD}"
        params = {}
    else:
        raise ValueError(kind)
    return {"glyph": glyph, "kind": kind, "params": params,
            "definition": definition, "f": f, "show": show}


ASCII_GLYPHS = ["@", "&", "$", "~"]   # fixed glyphs; MEANING randomized per problem
# Conventional ops: fixed glyph <-> meaning (easier).
ARITH_OPS = [
    ("add", "+"),
    ("sub", "-"),
    ("mul", "*"),
    ("div", "/"),
]


def sample_operator_table(rng, allow_div=True, ops_mode="ascii"):
    """Build the operator table for one problem."""
    if ops_mode == "arith":
        kinds_glyphs = list(ARITH_OPS)
        if not allow_div:
            kinds_glyphs = [(k, g) for k, g in kinds_glyphs if k != "div"]
        return [make_op(k, g, rng) for k, g in kinds_glyphs]

    # ascii: randomize glyph <-> meaning each problem.
    kinds = ["add", "mul"]                       # always present -> expressive
    pool = ["sub", "lin", "prodplus"] + (["div"] if allow_div else [])
    rng.shuffle(pool)
    while len(kinds) < 4 and pool:
        kinds.append(pool.pop())
    rng.shuffle(kinds)
    glyphs = list(ASCII_GLYPHS)
    rng.shuffle(glyphs)                          # randomize glyph <-> meaning
    return [make_op(k, g, rng) for k, g in zip(kinds, glyphs)]


# --------------------------------------------------------------------------- #
# Variable names
# --------------------------------------------------------------------------- #
def new_var(used, rng):
    while True:
        nm = rng.choice(LETTERS_1) + "#" + rng.choice(LETTERS_2)
        if nm not in used:
            used.add(nm)
            return nm


# --------------------------------------------------------------------------- #
# Expression building (left-to-right fold)
# --------------------------------------------------------------------------- #
def build_expr(rng, parents, mandatory, ops, value):
    n_terms = rng.choice([1, 2, 2, 3])
    term_vars = [mandatory]
    others = [p for p in parents if p != mandatory]
    rng.shuffle(others)
    while len(term_vars) < n_terms and (others or rng.random() < 0.4):
        if others and rng.random() < 0.7:
            term_vars.append(others.pop())
        else:
            term_vars.append(("const", rng.randint(2, 6)))
    rng.shuffle(term_vars)
    terms = [t if isinstance(t, tuple) else ("var", t) for t in term_vars]

    def tval(t):
        return value[t[1]] if t[0] == "var" else t[1] % MOD

    if len(terms) == 1:
        return terms, [], tval(terms[0])

    op_seq = []
    acc = tval(terms[0])
    for i in range(1, len(terms)):
        rv = tval(terms[i])
        choices = [o for o in ops if not (o["kind"] == "div" and rv % MOD == 0)]
        op = rng.choice(choices)
        op_seq.append(op)
        acc = op["f"](acc, rv)
    return terms, op_seq, acc


def term_str(t):
    return t[1] if t[0] == "var" else str(t[1])


def expr_str(terms, op_seq):
    if not op_seq:
        return term_str(terms[0])
    out = [term_str(terms[0])]
    for op, t in zip(op_seq, terms[1:]):
        out += [op["glyph"], term_str(t)]
    return " ".join(out)


# --------------------------------------------------------------------------- #
# Problem generation
# --------------------------------------------------------------------------- #
def generate_problem(rng, depth, n_distractors=2, allow_div=True, ops_mode="ascii"):
    ops = sample_operator_table(rng, allow_div=allow_div, ops_mode=ops_mode)
    used = set()
    layers, definitions, order, var_layer, value = {}, {}, [], {}, {}

    layers[1] = []
    for _ in range(rng.randint(2, 4)):
        v = new_var(used, rng)
        c = rng.randint(1, 6)
        definitions[v] = {"type": "const", "c": c}
        value[v] = c % MOD
        var_layer[v] = 1
        layers[1].append(v); order.append(v)

    for d in range(2, depth + 1):
        layers[d] = []
        n_nodes = rng.randint(2, 3) if d < depth else 1
        lower = [x for L in range(1, d) for x in layers[L]]
        for _ in range(n_nodes):
            v = new_var(used, rng)
            mandatory = rng.choice(layers[d - 1])
            terms, op_seq, val = build_expr(rng, lower, mandatory, ops, value)
            definitions[v] = {"type": "expr", "terms": terms, "ops": op_seq}
            value[v] = val
            var_layer[v] = d
            layers[d].append(v); order.append(v)

    query = layers[depth][-1]

    non_query = [x for x in order if x != query]
    for _ in range(n_distractors):
        v = new_var(used, rng)
        d = rng.randint(2, depth)
        eligible = [x for x in non_query if var_layer[x] < d]
        if not eligible:
            continue
        mandatory = rng.choice(eligible)
        terms, op_seq, val = build_expr(rng, eligible, mandatory, ops, value)
        definitions[v] = {"type": "expr", "terms": terms, "ops": op_seq}
        value[v] = val
        var_layer[v] = d
        order.append(v); non_query.append(v)

    answer = value[query]

    depth_of = {}
    for v in order:
        d = definitions[v]
        if d["type"] == "const":
            depth_of[v] = 1
        else:
            pv = [depth_of[t[1]] for t in d["terms"] if t[0] == "var"]
            depth_of[v] = 1 + (max(pv) if pv else 0)
    achieved_depth = depth_of[query]

    seen, stack = set(), [query]
    while stack:
        x = stack.pop()
        if x in seen:
            continue
        seen.add(x)
        d = definitions[x]
        if d["type"] == "expr":
            for t in d["terms"]:
                if t[0] == "var":
                    stack.append(t[1])
    necessary = seen

    op_lines = "  ".join(o["definition"] for o in ops)
    preamble = ("Operator definitions (evaluate strictly left to right, "
                f"all results mod {MOD}):  " + op_lines + ".")

    printed = list(order)
    rng.shuffle(printed)
    eq_lines = []
    for v in printed:
        d = definitions[v]
        rhs = str(d["c"]) if d["type"] == "const" else expr_str(d["terms"], d["ops"])
        eq_lines.append(f"{v} := {rhs}.")
    equations = " ".join(eq_lines)
    question = preamble + "\n\n" + equations + f" {query}?"

    cot = []
    for v in order:
        if v not in necessary:
            continue
        d = definitions[v]
        if d["type"] == "const":
            cot.append(f"{v} = {d['c']}  ->  {v} = {value[v]}")
            continue
        terms, op_seq = d["terms"], d["ops"]
        sym = expr_str(terms, op_seq)
        if not op_seq:
            cot.append(f"{v} = {sym} = {value[v]}")
            continue
        subbed = [str(value[t[1]]) if t[0] == "var" else str(t[1] % MOD) for t in terms]
        sub_line = subbed[0]
        for op, s in zip(op_seq, subbed[1:]):
            sub_line += f" {op['glyph']} {s}"
        block = [f"{v} = {sym}", f"    = {sub_line}"]
        acc = value[terms[0][1]] if terms[0][0] == "var" else terms[0][1] % MOD
        for op, t in zip(op_seq, terms[1:]):
            rv = value[t[1]] if t[0] == "var" else t[1] % MOD
            res = op["f"](acc, rv)
            block.append(f"    {acc} {op['glyph']} {rv} = {op['show'](acc, rv)} = {res}")
            acc = res
        block.append(f"    => {v} = {value[v]}")
        cot.append("\n".join(block))

    return {
        "mod": MOD,
        "ops_mode": ops_mode,
        "question": question,
        "preamble": preamble,
        "equations": equations,
        "query": query,
        "answer": answer,
        "cot": "\n".join(cot),
        "operator_table": [{"glyph": o["glyph"], "kind": o["kind"],
                            "params": o["params"], "definition": o["definition"]}
                           for o in ops],
        "target_depth": depth,
        "achieved_depth": achieved_depth,
        "num_vars": len(order),
        "num_necessary": len(necessary),
        "num_distractors": len(order) - sum(len(layers[d]) for d in layers),
        "var_layer": var_layer,
    }


# --------------------------------------------------------------------------- #
# Independent verifier
# --------------------------------------------------------------------------- #
def verify_record(rec):
    ops = {}
    for o in rec["operator_table"]:
        ops[o["glyph"]] = make_op(o["kind"], o["glyph"], params=o["params"] or None)["f"]

    defs = {}
    for chunk in rec["equations"].split("."):
        chunk = chunk.strip()
        if not chunk:
            continue
        name, rhs = chunk.split(" := ")
        defs[name.strip()] = rhs.strip().split()

    value = {}

    def resolve(v, stack=()):
        if v in value:
            return value[v]
        assert v not in stack, f"cycle at {v}"
        toks = defs[v]
        if len(toks) == 1:
            t = toks[0]
            value[v] = (int(t) % MOD) if t.isdigit() else resolve(t, stack + (v,))
            return value[v]

        def tv(t):
            return (int(t) % MOD) if t.isdigit() else resolve(t, stack + (v,))
        acc, i = tv(toks[0]), 1
        while i < len(toks):
            acc = ops[toks[i]](acc, tv(toks[i + 1]))
            i += 2
        value[v] = acc % MOD
        return value[v]

    got = resolve(rec["query"])
    assert got == rec["answer"], f"answer mismatch {got} != {rec['answer']}"
    assert rec["achieved_depth"] == rec["target_depth"], "depth mismatch"
    return True


# --------------------------------------------------------------------------- #
# Driver
# --------------------------------------------------------------------------- #
def main():
    ap = argparse.ArgumentParser()
    ap.add_argument("--n", type=int, default=100)
    ap.add_argument("--depths", type=int, nargs="+", default=[4, 5, 6])
    ap.add_argument("--distractors", type=int, default=2)
    ap.add_argument("--seed", type=int, default=0)
    ap.add_argument("--no-div", action="store_true")
    ap.add_argument("--ops", choices=["ascii", "arith"], default="ascii",
                    help="ascii: randomized @&$~ meanings; arith: fixed +-*/")
    ap.add_argument("--outdir", type=str, default=None,
                    help="default: out (ascii) or out_arith (arith)")
    args = ap.parse_args()

    if args.outdir is None:
        args.outdir = "out_arith" if args.ops == "arith" else "out"

    os.makedirs(args.outdir, exist_ok=True)
    rng = random.Random(args.seed)
    outfile = "igsm_mod7_arith.jsonl" if args.ops == "arith" else "igsm_mod7.jsonl"
    path = os.path.join(args.outdir, outfile)
    manifest = {
        "file": path, "ops": args.ops, "depths": {},
        "n_per_depth": args.n, "total_n": 0,
    }
    preview_recs = []
    id_prefix = "mod7_arith" if args.ops == "arith" else "mod7"

    with open(path, "w") as f:
        for depth in args.depths:
            answers, nec = [], []
            for i in range(args.n):
                rec = generate_problem(
                    rng, depth,
                    n_distractors=args.distractors,
                    allow_div=not args.no_div,
                    ops_mode=args.ops,
                )
                verify_record(rec)
                rec["id"] = f"{id_prefix}_d{depth}_{i:04d}"
                answers.append(rec["answer"]); nec.append(rec["num_necessary"])
                f.write(json.dumps(rec, ensure_ascii=False) + "\n")
                if i < 2:
                    preview_recs.append(rec)
            dist = {v: answers.count(v) for v in range(MOD)}
            manifest["depths"][f"d{depth}"] = {
                "n": args.n, "depth": depth,
                "random_baseline": round(1 / MOD, 4),
                "answer_hist": dist,
                "avg_necessary_nodes": round(sum(nec) / len(nec), 2),
            }
            manifest["total_n"] += args.n
            print(f"[d{depth}] wrote {args.n} verified examples -> {path}")
            print(f"        answers {dist}  | avg necessary nodes {manifest['depths'][f'd{depth}']['avg_necessary_nodes']}")

    with open(os.path.join(args.outdir, "manifest.json"), "w") as f:
        json.dump(manifest, f, indent=2, ensure_ascii=False)

    with open(os.path.join(args.outdir, "sample_preview.txt"), "w") as f:
        if args.ops == "arith":
            f.write("Operators + - * / have FIXED conventional meanings (mod 7). "
                    "Evaluate left-to-right.\n\n")
        else:
            f.write("Glyphs @ & $ ~ are fixed; their MEANING is randomized per "
                    "problem (see each problem's operator line). Left-to-right.\n\n")
        for r in preview_recs:
            f.write("=" * 74 + "\n")
            f.write(f"[{r['id']}]  depth={r['achieved_depth']}  vars={r['num_vars']} "
                    f"(necessary={r['num_necessary']}, distractors={r['num_distractors']})\n\n")
            f.write("Operators: " +
                    "  ".join(o["definition"] for o in r["operator_table"]) + "\n\n")
            f.write("Question. " + r["equations"] + f" {r['query']}?\n\n")
            f.write("Answer with CoT.\n" + r["cot"] + "\n")
            f.write(f"\n=> {r['query']} = {r['answer']}  (mod 7)\n\n")
    print(f"all depths -> {path}  (total {manifest['total_n']}, ops={args.ops})")
    print("preview ->", os.path.join(args.outdir, "sample_preview.txt"))


if __name__ == "__main__":
    main()