package reverse_think

import (
	"errors"
	"strings"
)

// Prompt carries the variables the Chinese reverse-thinking template
// renders. Field names align with the markdown SKILL.md template at
// ~/.claude/skills/reverse-think/SKILL.md.
//
// Prompt 携带渲染中文反向思维模板需要的变量. 字段名对齐
// ~/.claude/skills/reverse-think/SKILL.md 模板.
type Prompt struct {
	// Scenario describes the concrete context: language, files, fields,
	// current state. Required.
	//
	// Scenario 描述具体场景: 语言 / 文件 / 字段 / 当前状态. 必填.
	Scenario string

	// OptionA is the recommendation in one line.
	//
	// OptionA 是倾向选项 (一句话).
	OptionA string

	// OptionB is the alternative in one line.
	//
	// OptionB 是替代选项 (一句话).
	OptionB string

	// Recommendation is "A" or "B" -- which option the producer leans
	// toward before the reverse pass.
	//
	// Recommendation 是 "A" 或 "B" -- 反向思维前生产方倾向哪个.
	Recommendation string

	// RecommendationReason is two to three reasons backing Recommendation.
	//
	// RecommendationReason 是支持 Recommendation 的 2-3 个理由.
	RecommendationReason string
}

// ErrPromptIncomplete is returned by Render when any required field of
// Prompt is empty. Required = Scenario, OptionA, OptionB, Recommendation,
// RecommendationReason. The reverse pass cannot meaningfully challenge
// a recommendation that was never spelled out.
//
// ErrPromptIncomplete 在 Prompt 任一必填字段为空时由 Render 返回. 必填 =
// Scenario / OptionA / OptionB / Recommendation / RecommendationReason.
// 反向思维无法挑战一个没说清楚的方案.
var ErrPromptIncomplete = errors.New("reverse_think: prompt missing required field")

// Render produces the Chinese prompt string sent to the LLM. Output
// matches the SKILL.md template byte-for-byte under identical inputs so
// regression in prompt drift is catchable by golden test (see template_test).
//
// Render 产出发给 LLM 的中文 prompt 字符串. 输入相同时输出与 SKILL.md
// 模板字节对齐, prompt 漂移可由 golden test 锁住 (见 template_test).
func Render(p Prompt) (string, error) {
	if strings.TrimSpace(p.Scenario) == "" ||
		strings.TrimSpace(p.OptionA) == "" ||
		strings.TrimSpace(p.OptionB) == "" ||
		strings.TrimSpace(p.Recommendation) == "" ||
		strings.TrimSpace(p.RecommendationReason) == "" {
		return "", ErrPromptIncomplete
	}

	var b strings.Builder
	b.WriteString("你做反向思维分析, 直接给最终 JSON, 不要前后文.\n\n")
	b.WriteString("场景: ")
	b.WriteString(p.Scenario)
	b.WriteString("\n\n")
	b.WriteString("选项 A: ")
	b.WriteString(p.OptionA)
	b.WriteString("\n")
	b.WriteString("选项 B: ")
	b.WriteString(p.OptionB)
	b.WriteString("\n")
	b.WriteString("我的建议: ")
	b.WriteString(p.Recommendation)
	b.WriteString(" -- 理由 = ")
	b.WriteString(p.RecommendationReason)
	b.WriteString("\n\n")
	b.WriteString("你的任务: 反向思考 -- 如果我的建议是错的, 可能错在哪里?\n")
	b.WriteString("注意: 你的输出会进入主进程上下文, 长度有意义但请不要为了凑数列假问题.\n")
	b.WriteString("直接输出 JSON, 不要任何额外文字:\n")
	b.WriteString("{\n")
	b.WriteString(`  "hidden_assumptions": ["..."],` + "\n")
	b.WriteString(`  "failure_scenarios": ["..."],` + "\n")
	b.WriteString(`  "verdict": "A_holds | B_wins | depends_on_X",` + "\n")
	b.WriteString(`  "verdict_reason": "一两句话总结"` + "\n")
	b.WriteString("}\n")
	return b.String(), nil
}