"""Merged model dict -> C++ EngineModel codegen.

Plain `(dict) -> str`, no ESPHome/`cg`/`CORE` dependency (see
claude/DESCRIPTOR_REGISTRY_PLAN.md) - callable from display.py's to_code()
at ESPHome compile time, and from standalone host tooling
(check_descriptors.py and friends) outside any ESPHome build.
"""

from __future__ import annotations

from typing import Any

_LINE_ORDERS = {"SEQUENTIAL": "LineOrder::SEQUENTIAL", "PAIRED_EDGES": "LineOrder::PAIRED_EDGES"}


def _hex_bytes(s: str) -> list[int]:
    s = s or ""
    if len(s) % 2 != 0:
        raise ValueError(f"odd-length hex byte string: {s!r}")
    return [int(s[i : i + 2], 16) for i in range(0, len(s), 2)]


def _byte_array_literal(data: list[int]) -> str:
    return "{" + ", ".join(f"0x{b:02X}" for b in data) + "}"


def _emit_sequence(out: list[str], prefix: str, seq: list[dict]) -> tuple[str, int]:
    """Emits one EpdCommand table (and its per-entry data byte arrays) as
    `prefix`-named globals; returns (array name, length)."""
    entries = []
    for i, c in enumerate(seq):
        data = _hex_bytes(c.get("data", ""))
        data_name = "nullptr"
        if data:
            data_name = f"{prefix}_{i}_DATA"
            out.append(f"inline const uint8_t {data_name}[] = {_byte_array_literal(data)};")
        cmd = _hex_bytes(c["cmd"])[0]
        entries.append(
            "    {{0x{cmd:02X}, {data_name}, {data_len}, {before}, {after}, {wait}}},".format(
                cmd=cmd,
                data_name=data_name,
                data_len=len(data),
                before=c.get("delay_before_ms", 0),
                after=c.get("delay_after_ms", 0),
                wait="true" if c.get("wait_busy_after", False) else "false",
            )
        )
    seq_name = f"{prefix}_SEQ"
    if entries:
        out.append(f"inline const EpdCommand {seq_name}[] = {{")
        out.extend(entries)
        out.append("};")
    else:
        out.append(f"inline const EpdCommand *{seq_name} = nullptr;")
    return seq_name, len(entries)


def generate_cpp(model: dict[str, Any], var_name: str) -> str:
    """Generates one `inline const EngineModel {var_name} = {...};`
    plus its backing command/palette arrays, as a single translation unit's
    worth of text (no #pragma once / includes - the caller wraps this)."""
    out: list[str] = []
    prefix = var_name.upper()

    init_name, init_len = _emit_sequence(out, f"{prefix}_INIT", model["init_sequence"])
    refresh_name, refresh_len = _emit_sequence(out, f"{prefix}_REFRESH", model["refresh_sequence"])
    power_off_name, power_off_len = _emit_sequence(out, f"{prefix}_POWEROFF", model.get("power_off_sequence") or [])
    hibernate_name, hibernate_len = _emit_sequence(out, f"{prefix}_HIBERNATE", model.get("hibernate_sequence") or [])

    planes = model["planes"]
    if len(planes) > 2:
        raise ValueError(f"{var_name}: {len(planes)} planes given, engine supports at most 2")
    window_names: list[str] = ["nullptr", "nullptr"]
    window_lens: list[int] = [0, 0]
    plane_write_cmd: list[int] = [0, 0]
    plane_write_cmd_full: list[int] = [0, 0]
    plane_invert: list[bool] = [False, False]
    window_per_plane = False
    plane_width = 0
    base_window = planes[0].get("window_sequence")
    for i, p in enumerate(planes):
        window_seq = p.get("window_sequence") or (base_window if i == 0 else None)
        if window_seq is not None:
            if i > 0 and p.get("window_sequence") is not None:
                window_per_plane = True
            window_names[i], window_lens[i] = _emit_sequence(out, f"{prefix}_WINDOW{i}", window_seq)
        plane_write_cmd[i] = _hex_bytes(p["plane_write_cmd"])[0]
        plane_write_cmd_full[i] = _hex_bytes(p.get("plane_write_cmd_for_full_refresh", "00"))[0]
        plane_invert[i] = bool(p.get("plane_invert", False))
        if p.get("width") is not None:
            plane_width = p["width"]

    palette_name = "nullptr"
    palette_len = 0
    palette_entries = model.get("palette") or []
    if palette_entries:
        palette_name = f"{prefix}_PALETTE"
        out.append(f"inline const EpdPaletteEntry {palette_name}[] = {{")
        for e in palette_entries:
            r, g, b = _hex_bytes(e["rgb"])
            code = _hex_bytes(e["code"])[0]
            out.append(f"    {{0x{r:02X}, 0x{g:02X}, 0x{b:02X}, 0x{code:02X}}},")
        out.append("};")
        palette_len = len(palette_entries)

    out.append(f"inline const EngineModel {var_name} = {{")
    out.append(f"    .width = {model['width']},")
    out.append(f"    .height = {model['height']},")
    out.append(f"    .busy_active_level = {'true' if model['busy_active_level'] else 'false'},")
    out.append(f"    .busy_timeout_ms = {model['busy_timeout_ms']},")
    out.append(f"    .init_sequence = {init_name},")
    out.append(f"    .init_sequence_len = {init_len},")
    out.append(f"    .window_sequence = {{{window_names[0]}, {window_names[1]}}},")
    out.append(f"    .window_sequence_len = {{{window_lens[0]}, {window_lens[1]}}},")
    out.append(f"    .window_per_plane = {'true' if window_per_plane else 'false'},")
    out.append(f"    .plane_count = {len(planes)},")
    out.append(f"    .plane_write_cmd = {{0x{plane_write_cmd[0]:02X}, 0x{plane_write_cmd[1]:02X}}},")
    out.append(
        "    .plane_write_cmd_for_full_refresh = "
        f"{{0x{plane_write_cmd_full[0]:02X}, 0x{plane_write_cmd_full[1]:02X}}},"
    )
    out.append(f"    .plane_invert = {{{'true' if plane_invert[0] else 'false'}, {'true' if plane_invert[1] else 'false'}}},")
    out.append(f"    .plane_width = {plane_width},")
    out.append(f"    .line_order = {_LINE_ORDERS[model.get('line_order', 'SEQUENTIAL')]},")
    out.append(f"    .bits_per_pixel = {model.get('bits_per_pixel', 1)},")
    out.append(f"    .palette = {palette_name},")
    out.append(f"    .palette_len = {palette_len},")
    out.append(f"    .blank_code = 0x{model.get('blank_code', 0):02X},")
    out.append(f"    .refresh_sequence = {refresh_name},")
    out.append(f"    .refresh_sequence_len = {refresh_len},")
    out.append(f"    .power_off_sequence = {power_off_name},")
    out.append(f"    .power_off_sequence_len = {power_off_len},")
    out.append(f"    .hibernate_sequence = {hibernate_name},")
    out.append(f"    .hibernate_sequence_len = {hibernate_len},")
    out.append("};")
    return "\n".join(out) + "\n"