package model

import (
	"log/slog"
	"strings"
)

// Anthropic 扩展思考协议的边界（design/04 §3.2）。
const (
	// anthropicMinThinkingBudget 是 Messages API 在 thinking.type=enabled 时
	// 接受的最小 budget_tokens；低于它会被 400 拒绝，
	// 因此更低但非零的预算会被抬高并上报，而不是照发。
	anthropicMinThinkingBudget = 1024
	// anthropicDefaultThinkingBudget 在开启思考但未给
	// 显式预算时使用。
	anthropicDefaultThinkingBudget = 4096
	// anthropicThinkingBodyReserve 是在思考预算之上留给正文的空间：
	// max_tokens 由思考与可见答案共享，所以
	// 预算绝不允许把它全部吃光（design/04 §3.2 红线：
	// "预算与正文不得互相吃光").
	anthropicThinkingBodyReserve = 2048
)

// deepSeekAnthropicEndpoint 报告一次 Anthropic 协议请求是否
// 真的由 DeepSeek 的 /anthropic 端点服务。先检查 base URL，
// 因为是端点——而不是模型名——决定 budget_tokens 是否
// 被尊重，而 DeepSeek 端点常常配着一个非 DeepSeek 的
// 模型名（该服务会把未知名称静默映射到 deepseek-flash）。
func deepSeekAnthropicEndpoint(model, baseURL string) bool {
	if strings.Contains(strings.ToLower(baseURL), "deepseek") {
		return true
	}
	return reasoningVendorFor(model, baseURL) == vendorDeepSeek
}

// anthropicThinkingFor 解出扩展思考指令以及它所需的
// max_tokens。它返回（可能已被抬高的）max_tokens 与
// 线格式块；块为 nil 表示「不发送思考」（无指令，或
// 显式关闭）。由于 max_tokens 由思考与可见答案共享，
// 返回的预算总会为正文留下 anthropicThinkingBodyReserve，
// 而预算会吃光答案的请求则改为抬高 max_tokens——该
// 调整会被记录，因此绝不是一次静默改写。
//
// 这条规则只适用于 Anthropic 端点。DeepSeek 的 /anthropic 端点
// 会忽略 budget_tokens，所以它绝不能走这里（design/04 §3.2 事实 6）。
func anthropicThinkingFor(th *Thinking, maxTokens int, log *slog.Logger) (int, *anthropicThinking) {
	if th == nil || (th.Enable != nil && !*th.Enable) {
		return maxTokens, nil
	}
	budget := th.BudgetTokens
	if budget == 0 {
		budget = anthropicDefaultThinkingBudget
	}
	if budget < anthropicMinThinkingBudget {
		log.Warn("thinking budget raised to the protocol minimum",
			"provider", "anthropic", "field", "thinking.budget_tokens",
			"budget_tokens", th.BudgetTokens, "sent", anthropicMinThinkingBudget)
		budget = anthropicMinThinkingBudget
	}
	if need := budget + anthropicThinkingBodyReserve; maxTokens < need {
		log.Warn("max_tokens raised to leave room for thinking plus the answer",
			"provider", "anthropic", "budget_tokens", budget,
			"max_tokens_requested", maxTokens, "max_tokens_sent", need,
			"body_reserve", anthropicThinkingBodyReserve)
		maxTokens = need
	}
	return maxTokens, &anthropicThinking{Type: anthropicThinkingTypeEnabled, BudgetTokens: budget}
}

// anthropicDeepSeekReasoning 解出 DeepSeek /anthropic 请求的
// 推理旋钮。与 Anthropic 端点的两点差异决定了它：该
// 端点忽略 budget_tokens，所以 max_tokens 保持不动（抬高它
// 会错误反映提供商实际采用的预算），而强度由
// output_config.effort 控制，它没有 "none" 取值——在那里「关闭」
// 意图由 thinking 开关自身承载（design/04 §3.2 事实 2 与 6）。
func anthropicDeepSeekReasoning(log *slog.Logger, model string, th *Thinking, effort string) (*anthropicThinking, *anthropicOutputConfig) {
	var block *anthropicThinking
	if th != nil {
		if th.BudgetTokens > 0 {
			log.Warn("thinking.budget_tokens ignored by the DeepSeek /anthropic endpoint: strength is output_config.effort, so max_tokens was not raised for the budget",
				"provider", "deepseek", "field", "thinking.budget_tokens",
				"budget_tokens", th.BudgetTokens, "model", model)
		}
		switch {
		case th.Enable != nil:
			block = &anthropicThinking{Type: thinkingSwitchValue(*th.Enable), BudgetTokens: th.BudgetTokens}
		case th.BudgetTokens > 0:
			block = &anthropicThinking{Type: thinkingTypeEnabled, BudgetTokens: th.BudgetTokens}
		}
	}
	effort = strings.TrimSpace(effort)
	if effort == "" {
		return block, nil
	}
	if effort == effortNone {
		if block == nil || block.Type == thinkingTypeEnabled {
			log.Warn(`reasoning_effort none mapped to thinking.type=disabled: the DeepSeek /anthropic endpoint has no output_config.effort "none"`,
				"provider", "deepseek", "field", "reasoning_effort", "value", effort, "model", model)
		}
		return &anthropicThinking{Type: thinkingTypeDisabled}, nil
	}
	if block != nil && block.Type == thinkingTypeDisabled {
		log.Warn("output_config.effort dropped: thinking is explicitly disabled",
			"provider", "deepseek", "field", "reasoning_effort", "value", effort, "model", model)
		return block, nil
	}
	tier, ok := normalizeDeepSeekEffort(effort)
	if !ok {
		log.Warn("reasoning_effort dropped: unrecognized value",
			"provider", "deepseek", "field", "reasoning_effort", "value", effort, "model", model)
		return block, nil
	}
	if tier != effort {
		log.Warn("reasoning_effort alias normalized to the tier DeepSeek applies",
			"provider", "deepseek", "field", "reasoning_effort",
			"value", effort, "sent", tier, "model", model)
	}
	return block, &anthropicOutputConfig{Effort: tier}
}

// anthropicThinkingOn 报告一个已解出的 DeepSeek /anthropic 请求的
// 实际思考状态：省略开关会保留提供商默认值，而
// DeepSeek 的默认是开启。
func anthropicThinkingOn(th *anthropicThinking) bool {
	return th == nil || th.Type != thinkingTypeDisabled
}