First public commit.

lenser/basicgen.py

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+"""Generate a small, colourful Commodore 64 BASIC program (tokenised .PRG) that
+prints image metadata.  We emit the tokenised bytes directly -- token bytes for
+the few keywords used (PRINT, POKE) and PETSCII for everything else -- so there
+is no dependency on an external BASIC tokeniser.
+"""
+
+from __future__ import annotations
+
+# BASIC V2 keyword tokens.
+_PRINT = 0x99
+_POKE = 0x97
+_CHR = 0xC7        # CHR$( function token
+_QUOTE = 0x22
+
+# PETSCII control codes.
+CLR = 0x93
+RVON = 0x12
+RVOFF = 0x92
+# colours
+WHITE, RED, GREEN, BLUE = 0x05, 0x1c, 0x1e, 0x1f
+BLACK, ORANGE, BROWN = 0x90, 0x81, 0x95
+LT_RED, DK_GREY, GREY, LT_GREEN = 0x96, 0x97, 0x98, 0x99
+LT_BLUE, LT_GREY, PURPLE, YELLOW, CYAN = 0x9a, 0x9b, 0x9c, 0x9e, 0x9f
+
+# label colours cycled down the screen (none black, all readable on black).
+_LABEL_COLOURS = [CYAN, YELLOW, LT_GREEN, LT_RED, LT_BLUE, PURPLE, ORANGE, GREEN]
+# per-character rainbow for the title (bright, distinct, no black).
+_RAINBOW = [RED, ORANGE, YELLOW, LT_GREEN, GREEN, CYAN, LT_BLUE, BLUE, PURPLE,
+            LT_RED, WHITE]
+
+_SCREEN_W = 40
+_VALUE_COL = 11                # column where a value starts (= label field width)
+_LINE_MAX = _SCREEN_W - 1      # keep lines < 40 so the screen never auto-wraps
+_VALUE_W = _LINE_MAX - _VALUE_COL   # printable value chars per line
+
+
+def _petscii(text: str) -> bytes:
+    """Map an ASCII string to printable PETSCII (upper-case glyph range)."""
+    out = bytearray()
+    for ch in str(text).upper():
+        b = ord(ch)
+        if b == _QUOTE:
+            b = 0x27                       # avoid closing the BASIC string
+        if 0x20 <= b <= 0x5F:
+            out.append(b)
+        else:
+            out.append(0x2E)               # '.'
+    return bytes(out)
+
+
+def _print_str(inner: bytes) -> bytes:
+    return bytes([_PRINT, _QUOTE]) + inner + bytes([_QUOTE])
+
+
+def _assemble(lines: list[tuple[int, bytes]]) -> bytes:
+    """Link tokenised lines into a PRG (load address $0801)."""
+    cur = 0x0801
+    pieces = []
+    for num, toks in lines:
+        body = bytes([num & 0xFF, (num >> 8) & 0xFF]) + toks + b"\x00"
+        nxt = cur + 2 + len(body)
+        pieces.append(bytes([nxt & 0xFF, (nxt >> 8) & 0xFF]) + body)
+        cur = nxt
+    return bytes([0x01, 0x08]) + b"".join(pieces) + b"\x00\x00"
+
+
+def _rainbow_title(text: str) -> bytes:
+    """Centred, per-character rainbow title (control codes don't take columns)."""
+    pad = max(0, (_SCREEN_W - len(text)) // 2)
+    out = bytes([CLR]) + _petscii(" " * pad)
+    for k, ch in enumerate(text):
+        out += bytes([_RAINBOW[k % len(_RAINBOW)]]) + _petscii(ch)
+    return bytes([_PRINT, _QUOTE]) + out + bytes([_QUOTE])
+
+
+def _field_lines(label: str, value: str, colour: int) -> list[bytes]:
+    """Word-/width-wrapped PRINT lines for one field; continuations are indented
+    to the value's start column so a long value lines up under itself."""
+    label_p = _petscii((label + ":").ljust(_VALUE_COL))
+    value = str(value)[:_VALUE_W * 4]       # cap at four screen lines
+    chunks = [value[i:i + _VALUE_W] for i in range(0, len(value), _VALUE_W)] or [""]
+
+    out = [_print_str(bytes([colour]) + label_p + bytes([WHITE]) + _petscii(chunks[0]))]
+    indent = _petscii(" " * _VALUE_COL)
+    for chunk in chunks[1:]:
+        out.append(_print_str(bytes([WHITE]) + indent + _petscii(chunk)))
+    return out
+
+
+def build_info_prg(fields: list[tuple[str, str]]) -> bytes:
+    """Return a tokenised BASIC PRG that prints ``fields`` (label, value)."""
+    lines: list[tuple[int, bytes]] = []
+    num = 0
+
+    def add(toks: bytes):
+        nonlocal num
+        num += 10
+        lines.append((num, toks))
+
+    # border and background both black
+    add(bytes([_POKE]) + b"53280,0:" + bytes([_POKE]) + b"53281,0")
+    add(_rainbow_title("8 Bit Lenser picture info"))
+    add(bytes([_PRINT]))                    # blank line
+
+    for i, (label, value) in enumerate(fields):
+        col = _LABEL_COLOURS[i % len(_LABEL_COLOURS)]
+        for line in _field_lines(label, value, col):
+            add(line)
+
+    add(bytes([_PRINT]))
+    # PRINT " load "CHR$(34)"*"CHR$(34)",8,1 to view picture"   -- CHR$(34) is the
+    # double-quote, which can't appear literally inside a BASIC string.
+    q = bytes([_CHR]) + _petscii("(34)")
+    add(bytes([_PRINT])
+        + bytes([_QUOTE]) + bytes([GREY]) + _petscii(" load ") + bytes([_QUOTE])
+        + q
+        + bytes([_QUOTE]) + _petscii("*") + bytes([_QUOTE])
+        + q
+        + bytes([_QUOTE]) + _petscii(",8,1 to view picture") + bytes([_QUOTE]))
+    return _assemble(lines)