"""On-target hardware shims used by the Flask app.

Runs ON THE i.MX 8M Mini, not the host PC. Shells out to memtool, i2cget,
and /sys/kernel/debug/regmap. Cache bypass for SN65DSI83 is mandatory
before every IRQ_STAT read — see CLAUDE.md invariant 1.
"""

from __future__ import annotations

import logging
import re
import shlex
import signal
import subprocess
import time
from pathlib import Path
from typing import Optional

log = logging.getLogger(__name__)

SN65_REGMAP_DIR = "/sys/kernel/debug/regmap/4-002c"
SN65_I2C_BUS = 4
SN65_I2C_ADDR = 0x2C

DSIM_PHYTIMING_BASE = 0x32E100B4
DSIM_PHYTIMING_LEN = 0x0C

FB_BLANK_PATH = "/sys/class/graphics/fb0/blank"

# Held while a video pipeline is running so PUT /video stop can kill it.
_video_proc: Optional[subprocess.Popen] = None


# ---------------------------------------------------------------------------
# Process helpers
# ---------------------------------------------------------------------------

def _run(cmd: str, check: bool = True, timeout: float = 5.0) -> str:
    log.debug("run: %s", cmd)
    res = subprocess.run(
        shlex.split(cmd),
        capture_output=True,
        text=True,
        timeout=timeout,
    )
    if check and res.returncode != 0:
        raise RuntimeError(
            f"Command failed: {cmd}\nstderr: {res.stderr.strip()}"
        )
    return res.stdout


def _write_sysfs(path: str, value: str) -> None:
    Path(path).write_text(value)


# ---------------------------------------------------------------------------
# DSIM PHY_TIMING registers
# ---------------------------------------------------------------------------

def read_dsim_phy_timing() -> dict:
    """memtool md -l 0x32e100b4+0x0c → 3 little-endian 32-bit words.

    memtool prints lines like '0x32e100b4: 00000306 03120a04 00040707' —
    we strip the address prefix (everything up to and including the colon)
    before extracting hex words to avoid matching the address itself.
    """
    out = _run(f"memtool md -l 0x{DSIM_PHYTIMING_BASE:x}+0x{DSIM_PHYTIMING_LEN:x}")
    hex_words: list[str] = []
    for line in out.splitlines():
        if ":" in line:
            line = line.split(":", 1)[1]
        hex_words.extend(re.findall(r"\b([0-9a-fA-F]{8})\b", line))
    if len(hex_words) < 3:
        raise RuntimeError(f"memtool returned unexpected output:\n{out}")

    pt, pt1, pt2 = hex_words[:3]
    return {
        "PHY_TIMING": f"0x{pt}",
        "PHY_TIMING1": f"0x{pt1}",
        "PHY_TIMING2": f"0x{pt2}",
        "raw_hex": f"{pt} {pt1} {pt2}",
    }


# ---------------------------------------------------------------------------
# SN65DSI83 register map — regmap-bypassed
# ---------------------------------------------------------------------------

def _bypass_sn65_regmap_cache() -> None:
    bypass = Path(SN65_REGMAP_DIR) / "cache_bypass"
    try:
        bypass.write_text("1\n")
    except (FileNotFoundError, PermissionError) as e:
        log.warning("Could not bypass regmap cache (%s); falling back to i2cget", e)


def _read_sn65_regmap() -> dict[str, str]:
    """Read /sys/kernel/debug/regmap/2-002c/registers — returns {hex_addr: hex_val}."""
    regs_path = Path(SN65_REGMAP_DIR) / "registers"
    text = regs_path.read_text()
    out: dict[str, str] = {}
    for line in text.splitlines():
        m = re.match(r"\s*([0-9a-fA-F]+)\s*:?\s*([0-9a-fA-F]+)", line.strip())
        if m:
            out[m.group(1).lower().lstrip("0").rjust(2, "0")] = m.group(2).lower()
    return out


def _read_sn65_via_i2cget(reg: int) -> int:
    out = _run(f"i2cget -y -f {SN65_I2C_BUS} 0x{SN65_I2C_ADDR:02x} 0x{reg:02x}")
    return int(out.strip(), 16)


def read_sn65_registers() -> dict:
    """Cache-bypassed SN65DSI83 register read with explicit IRQ flags decoded.

    Critical: the bypass write must happen on every call — without it,
    IRQ_STAT (0xE5) returns the last cached value, not the current hardware
    state, and flicker events become invisible.
    """
    _bypass_sn65_regmap_cache()

    try:
        regs = _read_sn65_regmap()
        irq_raw = int(regs.get("e5", "0"), 16)
        pll_raw = int(regs.get("0a", "0"), 16)
        clk_raw = int(regs.get("0b", "0"), 16)
    except FileNotFoundError:
        regs = {}
        irq_raw = _read_sn65_via_i2cget(0xE5)
        pll_raw = _read_sn65_via_i2cget(0x0A)
        clk_raw = _read_sn65_via_i2cget(0x0B)
        regs = {
            "e5": f"{irq_raw:02x}",
            "0a": f"{pll_raw:02x}",
            "0b": f"{clk_raw:02x}",
        }

    return {
        "registers": regs,
        "pll_locked": bool(pll_raw & 0x80),
        "clk_detected": bool(clk_raw & 0x01),
        "irq_stat_raw": f"0x{irq_raw:02X}",
        "sot_err": bool(irq_raw & (1 << 4)),
        "synch_err": bool(irq_raw & (1 << 3)),
        "unc_ecc_err": bool(irq_raw & (1 << 6)),
    }


def settling_capture(duration_s: float = 2.0, interval_s: float = 0.1) -> list[dict]:
    """Sample SN65 registers at fixed cadence — catches transient LP→HS errors."""
    snapshots: list[dict] = []
    deadline = time.monotonic() + duration_s
    while time.monotonic() < deadline:
        snap = read_sn65_registers()
        snap["t_s"] = time.monotonic()
        snapshots.append(snap)
        time.sleep(interval_s)
    return snapshots


# ---------------------------------------------------------------------------
# Display / video control
# ---------------------------------------------------------------------------

def display_on() -> None:
    _write_sysfs(FB_BLANK_PATH, "0\n")


def display_off() -> None:
    _write_sysfs(FB_BLANK_PATH, "4\n")


_VIDEO_PIPELINES = {
    "static-pink": (
        "gst-launch-1.0 videotestsrc pattern=solid-color foreground-color=0xFFFF69B4 "
        "! video/x-raw,width=1280,height=800,framerate=60/1 "
        "! fbdevsink device=/dev/fb0"
    ),
}


def video_start(mode: str = "static-pink") -> None:
    global _video_proc
    if _video_proc is not None and _video_proc.poll() is None:
        video_stop()

    pipeline = _VIDEO_PIPELINES.get(mode)
    if pipeline is None:
        raise ValueError(f"Unknown video mode: {mode}")

    _video_proc = subprocess.Popen(
        shlex.split(pipeline),
        stdout=subprocess.DEVNULL,
        stderr=subprocess.DEVNULL,
        start_new_session=True,
    )


def video_stop() -> None:
    global _video_proc
    if _video_proc is None:
        return
    if _video_proc.poll() is None:
        try:
            import os
            os.killpg(os.getpgid(_video_proc.pid), signal.SIGTERM)
            _video_proc.wait(timeout=2.0)
        except (ProcessLookupError, subprocess.TimeoutExpired):
            try:
                _video_proc.kill()
            except ProcessLookupError:
                pass
    _video_proc = None