"""Google 图像模型（nano-banana / nano-banana-2 / nano-banana-2-lite / nano-banana-pro）提示词。

语义：Gemini 图像编辑 —— 原生主体保持能力强，输入图即"主体 + 底图"，
对自然语言指令遵循好。不套用 GPT 的编辑契约（冗长的拒绝条款反而稀释指令），
也不用负面清单（无 negative_prompt 参数）。要点：
  - 开头一句话钉死"主体 = 第一张图里的商品，逐像素保持"；
  - 指令自然语言描述目标画面（场景/排版/文案），不重述商品外观；
  - 标题/参数仅作识别背景并声明以图为准。
"""
from __future__ import annotations

from .common import TEXT_RENDER, requirements_block, resolve_style, selling_point_lines

_SUBJECT_LOCK = (
    "SUBJECT LOCK (highest priority): the product in the first image is the subject. "
    "Keep it exactly as photographed — same shape, proportions, colors, print/pattern, "
    "logo, label and every detail — and place that very product into the result. "
    "A second image, when present, is another view of the same product for reference only."
)

_QUALITY = (
    "OUTPUT: photorealistic commercial e-commerce photography, ultra-detailed, "
    "natural light and shadow, professional retouching."
)

_REMINDER = (
    "Reminder: keep the product exactly as in the first image; change only its surroundings, "
    "composition, lighting and overlay graphics."
)


def _anchor(ctx: dict) -> str:
    """商品文字锚定：仅供识别，明确以图为准（同 gpt 模块，避免文字反噬商品）。"""
    line = f"Context (identification only): the product is \"{ctx['title']}\""
    if ctx.get("params_line"):
        line += f" ({ctx['params_line']})"
    return line + ". The image, not this text, defines the product's appearance."


# ── 各图类型指令（自然语言编辑口吻）────────────────────────────────────────

def _task_white_bg(ctx: dict, lang: str) -> str:
    return (
        "Replace the background of this product photo with seamless pure white (RGB 255,255,255): "
        "product centered in front view filling about 85% of the frame, even studio lighting with only "
        "a faint natural contact shadow. No props, no added text, no background elements."
    )

def _task_key_features(ctx: dict, lang: str) -> str:
    sp = selling_point_lines(ctx, lang) or ctx["title"]
    return (
        "Create a square key-features infographic: the unchanged product on the left two-thirds, "
        "a clean right-hand panel with 3 feature callouts using minimal line icons and thin leader "
        f"lines pointing at the product. Callout copy: {sp}."
    )

def _task_selling_pt(ctx: dict, lang: str) -> str:
    sp = selling_point_lines(ctx, lang, 1) or ctx["title"]
    return (
        "Turn the photo into a single-selling-point poster: hero close-up of the unchanged product at "
        f"a dynamic angle, one large bold headline about \"{sp}\", generous negative space, and a small "
        "magnified circle zooming into an existing detail of the product."
    )

def _task_material(ctx: dict, lang: str) -> str:
    return (
        "Create an extreme macro close-up of an existing area of the product's surface, showing its "
        "true fabric weave / texture / stitching exactly as in the photo; shallow depth of field, "
        "raking light, small caption in a corner."
    )

def _task_lifestyle(ctx: dict, lang: str) -> str:
    return (
        "Place the unchanged product into a realistic everyday scene where it would naturally be used: "
        "human-scale surroundings, soft daylight, authentic candid mood, the product as the clear visual focus."
    )

def _task_multi_scene(ctx: dict, lang: str) -> str:
    sp = selling_point_lines(ctx, lang)
    task = (
        "Build a triptych of three vertical panels separated by thin gutters: each panel shows an "
        "identical copy of the product in a different usage scene (home interior / outdoor street / "
        "office desk), with consistent color grading across panels."
    )
    if sp:
        task += f" Panel captions: {sp}."
    return task

def _task_ecommerce_detail(ctx: dict, lang: str) -> str:
    sp = selling_point_lines(ctx, lang) or ctx["title"]
    params = ctx["params_line"]
    return (
        "Compose a square detail-page hero section: top half a hero banner with the unchanged product "
        "at a 3/4 angle; bottom half a clean spec card with 3 feature rows and line icons"
        + (f" (specs: {params})" if params else "")
        + f", one highlighted row: {sp}."
    )

def _task_size_chart(ctx: dict, lang: str) -> str:
    dims = ctx["params_line"]
    return (
        "Create a size chart: the unchanged product in clean front and side views on a light background, "
        "thin measurement annotation lines (arrows) marking length, width and height with values beside "
        "each line"
        + (f" (known specs: {dims})" if dims else "")
        + ", small caption row, precise technical-drawing aesthetic."
    )

def _task_sku_collection(ctx: dict, lang: str) -> str:
    # 不展开"全部配色"：会凭空造出新商品；只排列同一件的多个副本
    return (
        "Arrange several identical copies of the product in a neat equal grid (2-4 per row) with a small "
        "label chip below each copy; identical lighting and scale across copies. Every copy shows this "
        "exact product — do not invent other colorways or variants."
    )

_TASK_BUILDERS = {
    "white_bg": (_task_white_bg, False),
    "key_features": (_task_key_features, True),
    "selling_pt": (_task_selling_pt, True),
    "material": (_task_material, True),
    "lifestyle": (_task_lifestyle, True),
    "multi_scene": (_task_multi_scene, True),
    "ecommerce_detail": (_task_ecommerce_detail, True),
    "size_chart": (_task_size_chart, True),
    "sku_collection": (_task_sku_collection, True),
}


def build_prompt(type_id: str, ctx: dict, style_set: int, lang: str, extra: dict | None = None,
                 style_prompt: str | None = None, requirements: str | None = None) -> str:
    """构造指定图类型的 prompt：要求块 → 指令 → 主体锁 → 锚定 → 风格 → 文案 → 画质 → 提醒。"""
    style = resolve_style(style_set, style_prompt)
    extra = extra or {}
    hint = (extra.get("prompt_hint") or "").strip()

    if type_id == "custom":
        purpose = extra.get("title") or ""
        detail = extra.get("detail") or ""
        task = "Create an e-commerce marketing image featuring the product from the first image"
        task += f" — {purpose}" if purpose else ""
        task += f": {detail}" if detail else ""
        task += "."
        wants_text = True
    else:
        entry = _TASK_BUILDERS.get(type_id)
        if entry is None:
            raise ValueError(f"未知图类型: {type_id}")
        builder, wants_text = entry
        task = builder(ctx, lang)
    if hint:
        task += f" Composition guidance: {hint}."

    parts = [p for p in (requirements_block(requirements),) if p]
    parts.append(task)
    parts.append(_SUBJECT_LOCK)
    parts.append(_anchor(ctx))
    parts.append(f"Scene style (scene and background only, never the product): {style['tone']}.")
    if wants_text:
        parts.append(f"Text overlay (a graphic layer, never printed on the product): {TEXT_RENDER[lang]}")
    parts.append(_QUALITY)
    parts.append(_REMINDER)
    return "\n\n".join(parts)