slide_builder.py

"""
OpenDeck Slide Builder
Assembles a complete PPTX presentation from structured data + theme.
Handles gradient backgrounds, slide creation, and speaker notes.
"""

from lxml import etree
from pptx import Presentation
from pptx.util import Inches, Pt, Emu
from pptx.oxml.ns import qn

from themes import Theme, GradientStop
from layouts import render_slide, SLIDE_WIDTH, SLIDE_HEIGHT


# ─── GRADIENT BACKGROUND ──────────────────────────────────────────────────────

def _make_gradient_element(stops: list[GradientStop], angle: int):
    """
    Build an XML element for a gradient fill.
    Uses raw lxml because python-pptx doesn't support gradient backgrounds natively.
    """
    nsmap = {"a": "http://schemas.openxmlformats.org/drawingml/2006/main"}

    grad_fill = etree.SubElement(
        etree.Element("dummy"), qn("a:gradFill")
    )
    grad_fill.set("rotWithShape", "1")

    gs_lst = etree.SubElement(grad_fill, qn("a:gsLst"))

    for stop in stops:
        gs = etree.SubElement(gs_lst, qn("a:gs"))
        gs.set("pos", str(stop.position))
        srgb = etree.SubElement(gs, qn("a:srgbClr"))
        srgb.set("val", stop.color)

    lin = etree.SubElement(grad_fill, qn("a:lin"))
    lin.set("ang", str(angle))
    lin.set("scaled", "1")

    return grad_fill


def _apply_gradient_background(slide, stops: list[GradientStop], angle: int):
    """Apply a gradient fill to a slide's background."""
    if not stops:
        return

    bg = slide.background
    bg_elem = bg._element

    # Ensure <p:bgPr> exists
    bg_pr = bg_elem.find(qn("p:bgPr"))
    if bg_pr is None:
        bg_pr = etree.SubElement(bg_elem, qn("p:bgPr"))

    # Remove any existing fill
    for child in list(bg_pr):
        tag = child.tag
        if "Fill" in tag or "fill" in tag:
            bg_pr.remove(child)

    # Build the gradient fill
    grad_fill = _make_gradient_element(stops, angle)

    # Insert at the beginning of bgPr
    bg_pr.insert(0, grad_fill)

    # Ensure effectLst exists (required by PowerPoint)
    effect_lst = bg_pr.find(qn("a:effectLst"))
    if effect_lst is None:
        etree.SubElement(bg_pr, qn("a:effectLst"))


def _apply_solid_background(slide, color_hex: str):
    """Apply a solid color background to a slide."""
    bg = slide.background
    fill = bg.fill
    fill.solid()
    from pptx.dml.color import RGBColor
    fill.fore_color.rgb = RGBColor.from_string(color_hex)


# ─── SPEAKER NOTES ────────────────────────────────────────────────────────────

def _add_speaker_notes(slide, notes_text: str):
    """Add speaker notes to a slide."""
    if not notes_text:
        return

    notes_slide = slide.notes_slide
    notes_tf = notes_slide.notes_text_frame
    notes_tf.text = notes_text


# ─── SLIDE NUMBER ─────────────────────────────────────────────────────────────

def _add_slide_number(slide, current: int, total: int, theme: Theme):
    """Add a subtle slide number in the bottom-right corner."""
    from layouts import _add_text_box
    from pptx.enum.text import PP_ALIGN

    _add_text_box(
        slide,
        left=Inches(11.5),
        top=Inches(7.0),
        width=Inches(1.5),
        height=Inches(0.4),
        text=f"{current} / {total}",
        font_name=theme.body_font,
        font_size=Pt(10),
        font_color=theme.subtitle_color,
        alignment=PP_ALIGN.RIGHT,
    )


# ─── MAIN BUILDER ─────────────────────────────────────────────────────────────

def build_presentation(data: dict, theme: Theme, output_path: str) -> str:
    """
    Build a complete PPTX presentation.

    Args:
        data: Structured presentation data from LLM.
        theme: Theme object to apply.
        output_path: File path for the output .pptx file.

    Returns:
        The output file path.
    """
    prs = Presentation()

    # Set slide dimensions to 16:9 widescreen
    prs.slide_width = SLIDE_WIDTH
    prs.slide_height = SLIDE_HEIGHT

    slides_data = data.get("slides", [])
    total_slides = len(slides_data)

    for i, slide_data in enumerate(slides_data):
        slide_type = slide_data.get("type", "content")

        # Use blank layout (index 6) for full control
        slide_layout = prs.slide_layouts[6]
        slide = prs.slides.add_slide(slide_layout)

        # Choose gradient based on slide type
        if slide_type == "title":
            gradient = theme.title_bg_gradient or theme.bg_gradient
        elif slide_type in ("section", "closing"):
            gradient = theme.section_bg_gradient or theme.bg_gradient
        else:
            gradient = theme.bg_gradient

        # Apply gradient background
        if gradient:
            _apply_gradient_background(slide, gradient, theme.bg_gradient_angle)

        # Render the slide content using the appropriate layout
        render_slide(slide, slide_data, theme)

        # Add speaker notes
        notes = slide_data.get("notes", "")
        if notes:
            _add_speaker_notes(slide, notes)

        # Add slide number (skip title slide)
        if slide_type != "title" and slide_type != "closing":
            _add_slide_number(slide, i + 1, total_slides, theme)

    # Save the presentation
    prs.save(output_path)
    return output_path