"""
ui/code_templates.py

Code templates for derived channel kinds.

BUILTIN_TEMPLATES — shown as read-only previews for built-in kinds.
  "Edit as Custom Script" copies the template into custom_script.
  Uses exec-style: assign to `result`.

SCRIPT_TEMPLATES — default starter code shown when user picks a script kind.
  expression  → single Python expression (no assignment)
  function    → auto-wrapped as def compute(x, t): ... use return
  custom_script → exec-style block, assign to `result`

Namespace available in all kinds:
  x      — list of source values in source order
  <name> — each source's channel_id as a named variable (same as x[i])
  t      — elapsed time (seconds)
  math   — Python math module
  vars   — shared SignalProcessor._script_vars dict (read/write)
  state  — per-channel persistent dict (survives between evaluations)
"""

BUILTIN_TEMPLATES: dict = {

    "none": """\
result = x[0]
""",

    "derivative": """\
prev_v = state.get("v", x[0])
prev_t = state.get("t", t)
state["v"] = x[0]
state["t"] = t
result = (x[0] - prev_v) / (t - prev_t) if t != prev_t else 0.0
""",

    "derivative_channel": """\
prev_v = state.get("v", x[0])
prev_x = state.get("x", x[1])
state["v"] = x[0]
state["x"] = x[1]
result = (x[0] - prev_v) / (x[1] - prev_x) if x[1] != prev_x else 0.0
""",

    "second_derivative": """\
prev_v   = state.get("v", x[0])
prev_t   = state.get("t", t)
prev_vel = state.get("vel", 0.0)

cur_vel = (x[0] - prev_v) / (t - prev_t) if t != prev_t else 0.0
result  = (cur_vel - prev_vel) / (t - prev_t) if t != prev_t else 0.0

state["v"]   = x[0]
state["t"]   = t
state["vel"] = cur_vel
""",

    "second_derivative_channel": """\
prev_v   = state.get("v", x[0])
prev_x   = state.get("x", x[1])
prev_vel = state.get("vel", 0.0)

cur_vel = (x[0] - prev_v) / (x[1] - prev_x) if x[1] != prev_x else 0.0
result  = (cur_vel - prev_vel) / (x[1] - prev_x) if x[1] != prev_x else 0.0

state["v"]   = x[0]
state["x"]   = x[1]
state["vel"] = cur_vel
""",

    "rms": """\
import math as _math
buf = state.setdefault("buf", [])
buf.append(x[0])
window = 20
if len(buf) > window:
    buf.pop(0)
result = _math.sqrt(sum(v * v for v in buf) / len(buf))
""",

    "power": """\
result = x[0] * x[1]
""",

    "difference": """\
result = x[0] - x[1]
""",

    "sum": """\
result = sum(x)
""",
}


# Default starter code shown when user selects a script kind
SCRIPT_TEMPLATES: dict = {

    "expression": "x[0]",

    "function": """\
offset = vars.get("offset", 0)
return x[0] - offset
""",

    "custom_script": """\
zero = vars.get("zero", 0)
result = x[0] - zero
""",
}