"""Execution of a single automation step: locate the element, then click or type.

Shared by the CLI (clicker.py) and the automation runner (runner.py) so there is
one implementation of the safety checks. Callers differ only in how they report
progress and how they surface failures.
"""

import random

import focus


class StepError(Exception):
    """A step refused to run, or ran and could not be verified.

    `code` mirrors the CLI's exit codes: 3 = refused before acting,
    4 = acted but verification failed.
    """

    def __init__(self, message: str, code: int = 3):
        super().__init__(message)
        self.code = code


# Display scaling factors that actually exist. Anything else means the two sides
# are describing different things (usually a multi-monitor desktop) rather than a
# scaled single display.
KNOWN_SCALES = (1.0, 1.25, 1.5, 1.75, 2.0, 2.5, 3.0)


def scale_factor(found: dict, override: float | None, report=None) -> float:
    """CSS pixels and desktop pixels match on macOS and unscaled Windows, but
    Windows display scaling breaks that.

    Deliberately conservative: a raw ratio is only trusted when it lands on a real
    scaling factor. On a multi-monitor desktop the browser reports the display it
    is on while pyautogui reports the primary one, and the resulting ratio is
    meaningless — halving every coordinate would put clicks far from the target.
    Fall back to 1:1 and say so, rather than silently scaling.
    """
    if override is not None:
        return override

    try:
        import pyautogui
    except ImportError:
        return 1.0

    css_width = (found.get("screenSize") or {}).get("width")
    if not css_width:
        return 1.0

    os_width = pyautogui.size().width
    ratio = os_width / css_width

    for known in KNOWN_SCALES:
        if abs(ratio - known) < 0.02:
            return known

    if report:
        report(
            f"screen size disagrees (browser {css_width}px, OS {os_width}px, "
            f"ratio {ratio:.3f}) — assuming 1:1. If clicks land off, pass --scale."
        )
    return 1.0


def perform(
    dash,
    action: str,
    selector: str,
    *,
    index: int = 0,
    url: str = "",
    open_url: str = "",
    text: str | None = None,
    clear: bool = False,
    scale: float | None = None,
    timeout: float = 20.0,
    rng: random.Random | None = None,
    activate: bool = True,
    verify: bool = True,
    force: bool = False,
    dry_run: bool = False,
    robotic: bool = False,
    report=None,
    on_located=None,
) -> dict:
    """Run one step. Returns the located element's data.

    Raises DashboardError if the extension can't find it, StepError if the step
    is refused or fails verification.
    """
    import pyautogui
    import humanize

    rng = rng or random.Random()
    say = report or (lambda _m: None)

    found = dash.locate(selector, index, url, timeout, open_url)
    if on_located:
        on_located(found)

    if found.get("covered") and not force:
        raise StepError(
            f"{selector} is covered by {found.get('coveredBy')} — the click would hit that instead"
        )

    if action == "type" and not found.get("editable", True) and not force:
        kind = found.get("inputType")
        raise StepError(
            f"<{found['tag']}{f' type={kind}' if kind else ''}> is not an editable field "
            "(disabled, read-only, or not an input)"
        )

    factor = scale_factor(found, scale, report)
    x = found["screen"]["x"] * factor
    y = found["screen"]["y"] * factor

    screen_w, screen_h = pyautogui.size()
    if not (0 <= x < screen_w and 0 <= y < screen_h):
        raise StepError(
            f"target ({x:.0f}, {y:.0f}) is off-screen ({screen_w}x{screen_h}) — "
            "is the Chrome window on another display?"
        )

    say(f"at {x:.0f},{y:.0f}")

    # A click on a background window is consumed activating it and never reaches
    # the page, so raise the browser immediately before pressing.
    if activate:
        focused = focus.ensure_frontmost()
        say(focused.detail)
        if not focused.ok:
            raise StepError(
                "the browser is not frontmost — the click would be consumed "
                "activating its window instead of pressing the element"
            )

    pyautogui.FAILSAFE = True

    if robotic:
        pyautogui.moveTo(x, y, duration=0.25)
        if not dry_run:
            pyautogui.click()
    else:
        humanize.click(x, y, rng=rng, press=not dry_run)

    if action == "click" or dry_run:
        return found

    # ── type ────────────────────────────────────────────────────────────────
    import time
    time.sleep(0.15)   # let the field take focus and any JS handlers settle

    if clear:
        humanize.clear_field(rng)
    humanize.type_text(text or "", rng)

    if not verify:
        return found

    # Typing into a field that never took focus, or that ignores the input, fails
    # silently and is otherwise indistinguishable from success.
    after = dash.locate(selector, index, url, timeout, open_url)
    got = after.get("value")
    if got is None:
        say("element exposes no value to verify against")
        return found
    if (text or "") in got:
        say(f"verified, field contains {got!r}")
        return after

    raise StepError(f"verification failed — field contains {got!r}", code=4)