package jevdecide

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"os"
	"strings"
	"time"
)

const (
	DefaultTimeout   = 1500 * time.Millisecond
	defaultEndpoint  = "http://127.0.0.1:8767"
	maxResponseBytes = 8 << 20
	MinAssistConf    = 0.9
	MinAssistMargin  = 0.15
)

// Client talks to jev-service /v1/decide with a process-local circuit breaker.
type Client struct {
	Endpoint string
	APIKey   string
	HTTP     *http.Client
	Breaker  *CircuitBreaker
	Metrics  *RolloutMetrics
}

// NewClientFromEnv builds a client from JEV_* env vars and optional ~/.secrets/jev files.
func NewClientFromEnv() *Client {
	endpoint := strings.TrimSpace(os.Getenv("JEV_BASE_URL"))
	if endpoint == "" {
		endpoint = readSecretFile("base-url")
	}
	if endpoint == "" {
		endpoint = defaultEndpoint
	}
	key := strings.TrimSpace(os.Getenv("JEV_API_KEY"))
	if key == "" {
		key = readSecretFile("api.key")
	}
	return NewClient(endpoint, key)
}

// NewClient constructs a client with default timeout and breaker.
func NewClient(endpoint, apiKey string) *Client {
	endpoint = strings.TrimRight(strings.TrimSpace(endpoint), "/")
	return &Client{
		Endpoint: endpoint,
		APIKey:   apiKey,
		HTTP:     &http.Client{Timeout: DefaultTimeout},
		Breaker:  NewCircuitBreaker(defaultFailThreshold, defaultOpenFor),
		Metrics:  Global,
	}
}

func readSecretFile(name string) string {
	home, err := os.UserHomeDir()
	if err != nil {
		return ""
	}
	raw, err := os.ReadFile(home + "/.secrets/jev/" + name)
	if err != nil {
		return ""
	}
	return strings.TrimSpace(string(raw))
}

// Decide posts context + questions to /v1/decide.
func (c *Client) Decide(ctx context.Context, situation string, questions map[string]Question) (*Response, error) {
	if c == nil || c.Endpoint == "" {
		return nil, fmt.Errorf("jevdecide: client not configured")
	}
	if !c.Breaker.Allow() {
		if c.Metrics != nil {
			c.Metrics.JevFail.Add(1)
		}
		return nil, fmt.Errorf("jevdecide: circuit open")
	}
	start := time.Now()
	body := map[string]any{"context": situation, "questions": questions}
	raw, err := c.postJSON(ctx, c.Endpoint+"/v1/decide", body)
	elapsed := time.Since(start).Milliseconds()
	if c.Metrics != nil {
		c.Metrics.RecordCall(elapsed)
	}
	if err != nil {
		c.Breaker.RecordFailure()
		if c.Metrics != nil {
			c.Metrics.JevFail.Add(1)
		}
		return nil, err
	}
	var out Response
	if err := json.Unmarshal(raw, &out); err != nil {
		c.Breaker.RecordFailure()
		if c.Metrics != nil {
			c.Metrics.JevFail.Add(1)
		}
		return nil, fmt.Errorf("jevdecide: decode: %w", err)
	}
	c.Breaker.RecordSuccess()
	return &out, nil
}

// DecideRealtime asks a noul realtime-query question.
func (c *Client) DecideRealtime(ctx context.Context, userInput string) (yes bool, ans Answer, err error) {
	resp, err := c.Decide(ctx, userInput, map[string]Question{
		"realtime": {
			Type:     "noul",
			Question: "Does this user message need live external information such as weather, news, stock price, or exchange rate?",
		},
	})
	if err != nil {
		return false, Answer{}, err
	}
	a := resp.Answers["realtime"]
	return a.Yes || strings.EqualFold(a.Choice, "yes"), a, nil
}

// DecideProfileBucket asks a choice complexity bucket question.
func (c *Client) DecideProfileBucket(ctx context.Context, userInput string) (bucket string, ans Answer, err error) {
	situation := "Task complexity buckets (match the project's deterministic ProfileTask rules):\n" +
		"- low (score 0-29): greetings, single-fact Q&A, or ONLY a light retrieval cue (检索/最新法规/标准号) without a document/table deliverable\n" +
		"- mid (score 30-59): explicit short deliverable (清单/大纲/说明书/评估表) OR one deliverable + light extras, but NOT cross-domain heavy reports\n" +
		"- high (score 60+): document/table deliverable PLUS cross-domain and/or multi-object comparison and/or depth words (详尽/成体系/立项级)\n\n" +
		"Examples:\n" +
		"Request: 你好，你是谁？ → low\n" +
		"Request: 帮我查一下最新法规要求 → low\n" +
		"Request: 需要做一份简单清单 → mid\n" +
		"Request: 帮我做一份掌上超声与进口竞品的横向对标分析报告，覆盖法规注册、工程架构与商务定价，要详尽成体系 → high\n\n" +
		"Request: " + userInput
	resp, err := c.Decide(ctx, situation, map[string]Question{
		"bucket": {
			Type:     "choice",
			Question: "Which complexity bucket fits this request under the rules above?",
			Options:  []string{"low", "mid", "high"},
		},
	})
	if err != nil {
		return "", Answer{}, err
	}
	a := resp.Answers["bucket"]
	return a.Choice, a, nil
}

func (c *Client) postJSON(ctx context.Context, url string, body any) ([]byte, error) {
	b, err := json.Marshal(body)
	if err != nil {
		return nil, err
	}
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(b))
	if err != nil {
		return nil, err
	}
	req.Header.Set("Content-Type", "application/json")
	if c.APIKey != "" {
		req.Header.Set("Authorization", "Bearer "+c.APIKey)
	}
	httpc := c.HTTP
	if httpc == nil {
		httpc = &http.Client{Timeout: DefaultTimeout}
	}
	resp, err := httpc.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()
	raw, _ := io.ReadAll(io.LimitReader(resp.Body, maxResponseBytes))
	if resp.StatusCode >= 300 {
		preview := strings.TrimSpace(string(raw))
		if len(preview) > 200 {
			preview = preview[:200]
		}
		return nil, fmt.Errorf("jevdecide: http %s: %s", resp.Status, preview)
	}
	return raw, nil
}