// Package agent wires real LLM-driven planner and work agents (on top of the
// agent-core SDK) to the dual SQLite graph. See docs/ARTEX-架构设计.md
// §4.3 (planner) and §4.4 (work agent).
//
// Provider configuration is read from the environment so the system runs with
// any Anthropic- or OpenAI-format endpoint. If no key is configured, FromEnv
// returns ok=false and the exploration engine stays idle (an LLM is required).
package agent

import (
	"bytes"
	"context"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"os"
	"regexp"
	"strings"
	"time"

	"github.com/Autumn-27/norma/agentcore"
	"github.com/Autumn-27/norma/compaction"
	"github.com/Autumn-27/norma/llm"
	acperm "github.com/Autumn-27/norma/permission"
)

// Config describes the LLM backend resolved from the environment.
type Config struct {
	Format  llm.Format
	BaseURL string
	APIKey  string
	Model   string
	// Proxy routes all LLM requests through the given proxy URL (http/https/socks5).
	// Empty falls back to the standard *_PROXY environment variables.
	Proxy string
	// RatePerSecond / RatePerMinute cap the shared request rate across ALL agents
	// using the provider (0 = that window unlimited).
	RatePerSecond float64
	RatePerMinute float64
	// ContextWindowK is the model's context window in K tokens (user-configured),
	// used to size compaction thresholds. 0 = default; see CompactionWindow.
	ContextWindowK int
	// ThinkingType 独立控制思考「开关」字段(thinking.type):
	//   "" = 不发送(默认,兼容不支持该字段的模型); "disabled" = 显式关闭;
	//   "enabled" = 开启. 与 ReasoningEffort 完全解耦——有些接口没有 thinking 字段、
	//   只靠强度参数就能激活思考,故两者可各自单独设置.
	ThinkingType string
	// ReasoningEffort 独立控制思考「强度」字段:
	//   "" = 不发送(默认); "low"/"medium"/"high"/"xhigh"/"max" = 对应强度.
	//   OpenAI 映射为顶层 reasoning_effort;Anthropic 映射为 output_config.effort.
	ReasoningEffort string
}

// compaction window resolution bounds (in K tokens). Below the floor the
// threshold math (window − summary reserve − buffer) would go non-positive and
// compaction would fire every turn; above the cap it would never fire.
const (
	defaultWindowK = 200  // unset → assume a 200K window (Claude default)
	minWindowK     = 32   // floor so effectiveWindow stays comfortably positive
	maxWindowK     = 1000 // cap at 1M tokens (user request)
)

// CompactionWindow returns the model context window in TOKENS for compaction
// thresholds, resolved from the user-configured size (ContextWindowK). 0/unset →
// a 200K default; otherwise clamped to [32K, 1M] so compaction stays effective.
func (c Config) CompactionWindow() int {
	k := c.ContextWindowK
	if k <= 0 {
		k = defaultWindowK
	}
	if k < minWindowK {
		k = minWindowK
	}
	if k > maxWindowK {
		k = maxWindowK
	}
	return k * 1000
}

// compactionConfig builds the agent-core compaction config for a context window
// in tokens. agentcore.NewSession wires the summarizer (same provider) when this
// is set on Options.Compaction.
func compactionConfig(windowTokens int) *compaction.Config {
	if windowTokens <= 0 {
		windowTokens = defaultWindowK * 1000
	}
	return &compaction.Config{ContextWindow: windowTokens}
}

// FromEnv resolves the LLM provider config:
//
//	ARTEX_LLM_PROVIDER = anthropic|openai (default: inferred from keys)
//	ARTEX_LLM_MODEL    = model id        (default: per provider)
//	ARTEX_LLM_BASE_URL = endpoint        (optional)
//	ARTEX_LLM_PROXY    = proxy URL        (optional; http/https/socks5)
//	ANTHROPIC_API_KEY / OPENAI_API_KEY         = credentials
func FromEnv() (Config, bool) {
	prov := os.Getenv("ARTEX_LLM_PROVIDER")
	anthKey := os.Getenv("ANTHROPIC_API_KEY")
	oaiKey := os.Getenv("OPENAI_API_KEY")

	if prov == "" {
		switch {
		case anthKey != "":
			prov = "anthropic"
		case oaiKey != "":
			prov = "openai"
		default:
			return Config{}, false
		}
	}

	c := Config{
		BaseURL: os.Getenv("ARTEX_LLM_BASE_URL"),
		Model:   os.Getenv("ARTEX_LLM_MODEL"),
		Proxy:   strings.TrimSpace(os.Getenv("ARTEX_LLM_PROXY")),
	}
	switch prov {
	case "openai":
		c.Format = llm.FormatOpenAI
		c.APIKey = oaiKey
		if c.Model == "" {
			c.Model = "gpt-4o"
		}
	default:
		c.Format = llm.FormatAnthropic
		c.APIKey = anthKey
		if c.Model == "" {
			c.Model = "claude-opus-4-8"
		}
	}
	if c.APIKey == "" {
		return Config{}, false
	}
	return c, true
}

// ConfigFrom builds a Config from UI-provided strings (provider defaults to
// anthropic; model defaults per provider). Inputs are trimmed and the base URL
// is normalized to the API base the provider expects (the provider appends the
// endpoint path itself), so a full endpoint URL is tolerated.
func ConfigFrom(provider, model, baseURL, apiKey, proxy string) Config {
	c := Config{
		Model:   strings.TrimSpace(model),
		BaseURL: strings.TrimRight(strings.TrimSpace(baseURL), "/"),
		APIKey:  strings.TrimSpace(apiKey),
		Proxy:   strings.TrimSpace(proxy),
	}
	switch strings.TrimSpace(provider) {
	case "openai":
		c.Format = llm.FormatOpenAI
		// provider appends "/chat/completions"; tolerate a full endpoint URL.
		c.BaseURL = strings.TrimRight(strings.TrimSuffix(c.BaseURL, "/chat/completions"), "/")
		if c.Model == "" {
			c.Model = "gpt-4o"
		}
	default:
		c.Format = llm.FormatAnthropic
		// provider appends "/v1/messages".
		c.BaseURL = strings.TrimRight(strings.TrimSuffix(c.BaseURL, "/v1/messages"), "/")
		if c.Model == "" {
			c.Model = "claude-opus-4-8"
		}
	}
	return c
}

// Provider returns the short provider name ("anthropic"/"openai").
func (c Config) Provider() string {
	if c.Format == llm.FormatOpenAI {
		return "openai"
	}
	return "anthropic"
}

// NewProvider builds an llm.Provider from the config. When a rate is set, the
// limiter lives on the single provider instance — so planner + all workers +
// main agent (which share this provider) are bounded by one shared rate limit.
func (c Config) NewProvider() (llm.Provider, error) {
	client, err := quotaAwareHTTPClient(c.Proxy)
	if err != nil {
		return nil, err
	}
	lc := llm.Config{
		Format:     c.Format,
		BaseURL:    c.BaseURL,
		APIKey:     c.APIKey,
		Model:      c.Model,
		HTTPClient: client,
	}
	// 思考开关与强度两个字段各自透传(空 = 该字段不发送)。二者解耦:
	// 可只发 thinking.type、只发 effort、都发、或都不发。
	lc.ThinkingType = c.ThinkingType
	lc.ReasoningEffort = c.ReasoningEffort
	if c.RatePerSecond > 0 || c.RatePerMinute > 0 {
		lc.RateLimit = &llm.RateLimit{PerSecond: c.RatePerSecond, PerMinute: c.RatePerMinute}
	}
	return llm.NewProvider(lc)
}

// IsQuotaExhaustedMessage deliberately recognizes only explicit balance,
// billing, credit, or quota-exhaustion signals. Generic 429/rate-limit text,
// authentication failures, network errors, and server failures are excluded.
var nonFailoverHTTPStatus = regexp.MustCompile(`(?:status(?:\s+code)?|http(?:\s+status)?)\s*[=:]?\s*(?:401|403|5\d\d)\b`)
var transientQuotaLimit = regexp.MustCompile(`(?i)(?:\b(?:rpm|tpm|rpd|qps)\b|quota[_\s-]*metric|rate[_\s-]*limit|too many requests|(?:requests?|tokens?)\s+(?:per|/)\s*(?:second|minute)|(?:per|/)\s*(?:second|minute)\s+(?:requests?|tokens?)|generate[_\s-]*requests[_\s-]*per[_\s-]*(?:minute|second)|tokens?[_\s-]*per[_\s-]*(?:minute|second))`)

func IsQuotaExhaustedMessage(message string) bool {
	message = strings.ToLower(message)
	// Authentication/authorization and provider-side 5xx failures never rotate,
	// even when a gateway happens to echo a quota-looking phrase in the body.
	if nonFailoverHTTPStatus.MatchString(message) {
		return false
	}
	// Provider APIs frequently describe an ordinary rate limit as "quota
	// exceeded", especially Google-style responses containing a quota metric.
	// These limits recover with time and must stay on the current provider.
	if transientQuotaLimit.MatchString(message) {
		return false
	}
	markers := []string{
		"insufficient_quota", "quota_exceeded", "quota exceeded", "quota exhausted",
		"exceeded your current quota", "billing_hard_limit_reached",
		"billing hard limit", "billing_not_active", "credit balance", "insufficient credit",
		"insufficient balance", "balance is too low", "payment required", "status 402",
		"余额不足", "额度不足", "额度已用尽", "欠费",
	}
	for _, marker := range markers {
		if strings.Contains(message, marker) {
			return true
		}
	}
	// gRPC RESOURCE_EXHAUSTED is overloaded for both account quota and ordinary
	// request-rate limiting. Preserve it as an explicit exhaustion signal only
	// when the same error does not identify a transient rate limit.
	return strings.Contains(message, "resource_exhausted") &&
		!strings.Contains(message, "rate limit") &&
		!strings.Contains(message, "too many requests")
}

// quotaAwareTransport preserves Norma's normal retry behavior except for a 429
// whose body explicitly says the account quota/balance is exhausted. Norma's
// retry loop treats every 429 as transient; normalizing only that response to
// 402 lets a task router fail over immediately while retaining the original
// response body for provider-specific classification and audit logs.
type quotaAwareTransport struct{ base http.RoundTripper }

func (t quotaAwareTransport) RoundTrip(req *http.Request) (*http.Response, error) {
	resp, err := t.base.RoundTrip(req)
	if err != nil || resp == nil || resp.StatusCode != http.StatusTooManyRequests {
		return resp, err
	}
	body, readErr := io.ReadAll(resp.Body)
	_ = resp.Body.Close()
	resp.Body = io.NopCloser(bytes.NewReader(body))
	resp.ContentLength = int64(len(body))
	if readErr != nil {
		return resp, nil
	}
	if IsQuotaExhaustedMessage(string(body)) {
		resp.StatusCode = http.StatusPaymentRequired
		resp.Status = "402 Payment Required"
	}
	return resp, nil
}

func quotaAwareHTTPClient(proxy string) (*http.Client, error) {
	transport := http.DefaultTransport.(*http.Transport).Clone()
	proxy = strings.TrimSpace(proxy)
	if proxy == "" {
		transport.Proxy = http.ProxyFromEnvironment
	} else {
		proxyURL, err := url.Parse(proxy)
		if err != nil {
			return nil, fmt.Errorf("llm: invalid proxy %q: %w", proxy, err)
		}
		switch proxyURL.Scheme {
		case "http", "https", "socks5":
		case "":
			return nil, fmt.Errorf("llm: proxy %q missing scheme (use http://, https:// or socks5://)", proxy)
		default:
			return nil, fmt.Errorf("llm: unsupported proxy scheme %q (use http, https or socks5)", proxyURL.Scheme)
		}
		transport.Proxy = http.ProxyURL(proxyURL)
	}
	return &http.Client{Transport: quotaAwareTransport{base: transport}}, nil
}

// TestConnection makes a minimal real completion to verify the provider/model/
// endpoint/key actually work. Returns the round-trip latency.
func TestConnection(ctx context.Context, c Config) (time.Duration, error) {
	prov, err := c.NewProvider()
	if err != nil {
		return 0, err
	}
	ctx, cancel := context.WithTimeout(ctx, 30*time.Second)
	defer cancel()
	start := time.Now()
	// MaxTokens 要给足：推理模型(如 deepseek-v4-pro)在给出答案前会先产出一大段
	// 思考(实测对一句 "ping" 也能烧 ~2900 token)。若只给 32,模型会一直卡在"思考阶段"
	// 就撞到输出上限(finish=length)、被截断,连接测试虽仍算通(err=nil)但显示成
	// "已中断/length/resume" 一团糟。给足预算让它把 OK 干净吐完(finish=stop)。
	// EscalateMaxTokens 保持 false:不因截断而抬额重试,避免 resume 循环空烧。
	_, err = agentcore.Run(ctx, agentcore.Options{
		Provider:       prov,
		SystemPrompt:   []string{"你是连接测试。直接输出两个字符 OK 即可，不要思考、不要解释、不要别的。"},
		PermissionMode: acperm.ModeBypass,
		MaxTurns:       1,
		MaxTokens:      8192,
	}, "ping")
	return time.Since(start), err
}