package tools

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

	core "agent-system-core"
)

// execHTTPTool 见 HTTPExecutor：声明式 HTTP 工具在注册时绑定 spec 闭包执行。
func HTTPExecutor(spec core.HTTPToolSpec, settingsLookup func(key string) string) Executor {
	return func(rc ToolExecCtx, args json.RawMessage) (string, error) {
		params := map[string]any{}
		if len(args) > 0 {
			if err := json.Unmarshal(args, &params); err != nil {
				return "", fmt.Errorf("http tool: bad args json: %w", err)
			}
		}
		method := strings.ToUpper(spec.Method)
		if method == "" {
			method = http.MethodGet
		}
		urlStr := expandTemplate(spec.URL, params)
		var body io.Reader
		if spec.BodyTemplate != "" && (method == http.MethodPost || method == http.MethodPut || method == http.MethodPatch) {
			body = bytes.NewReader([]byte(expandTemplate(spec.BodyTemplate, params)))
		}
		req, err := http.NewRequest(method, urlStr, body)
		if err != nil {
			return "", err
		}
		for k, v := range spec.Headers {
			req.Header.Set(k, expandTemplate(v, params))
		}
		if body != nil && req.Header.Get("Content-Type") == "" {
			req.Header.Set("Content-Type", "application/json")
		}
		if spec.AuthRef != "" {
			token := authValue(spec.AuthRef, settingsLookup)
			if token != "" {
				if strings.HasPrefix(token, "Bearer ") || strings.Contains(token, " ") {
					req.Header.Set("Authorization", token)
				} else {
					req.Header.Set("Authorization", "Bearer "+token)
				}
			}
		}
		timeout := time.Duration(spec.TimeoutMs) * time.Millisecond
		if timeout <= 0 {
			timeout = 15 * time.Second
		}
		client := &http.Client{Timeout: timeout}
		resp, err := client.Do(req)
		if err != nil {
			return "", fmt.Errorf("http tool: %w", err)
		}
		defer resp.Body.Close()
		raw, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
		if err != nil {
			return "", fmt.Errorf("http tool: read body: %w", err)
		}
		if resp.StatusCode >= 400 {
			return "", fmt.Errorf("http tool: status %d: %s", resp.StatusCode, truncateStr(string(raw), 400))
		}
		// JSON 则裁剪路径；否则原文返回。
		var parsed any
		if err := json.Unmarshal(raw, &parsed); err == nil {
			if spec.ResultPath != "" {
				if v, ok := pickPath(parsed, spec.ResultPath); ok {
					return prettyJSON(v), nil
				}
				return "", fmt.Errorf("http tool: result path %q not found", spec.ResultPath)
			}
			return prettyJSON(parsed), nil
		}
		return truncateStr(string(raw), 20000), nil
	}
}

// expandTemplate 替换 {{param.x.y}}；未知变量替换为空串（防注入：无脚本语义）。
func expandTemplate(tpl string, params map[string]any) string {
	out := tpl
	for {
		start := strings.Index(out, "{{")
		if start < 0 {
			break
		}
		end := strings.Index(out[start:], "}}")
		if end < 0 {
			break
		}
		end += start
		key := strings.TrimSpace(out[start+2 : end])
		key = strings.TrimPrefix(key, "param.") // {{param.x}} → 顶层参数 x
		val := ""
		if v, ok := lookup(params, key); ok {
			val = fmt.Sprint(v)
		}
		out = out[:start] + val + out[end+2:]
	}
	return out
}

func lookup(params map[string]any, dotted string) (any, bool) {
	parts := strings.Split(dotted, ".")
	var cur any = params
	for _, p := range parts {
		m, ok := cur.(map[string]any)
		if !ok {
			return nil, false
		}
		cur, ok = m[p]
		if !ok {
			return nil, false
		}
	}
	return cur, true
}

func pickPath(v any, dotted string) (any, bool) {
	parts := strings.Split(dotted, ".")
	cur := v
	for _, p := range parts {
		// 数组支持 "0" 数字索引
		if arr, ok := cur.([]any); ok {
			idx := -1
			fmt.Sscanf(p, "%d", &idx)
			if idx < 0 || idx >= len(arr) {
				return nil, false
			}
			cur = arr[idx]
			continue
		}
		m, ok := cur.(map[string]any)
		if !ok {
			return nil, false
		}
		cur, ok = m[p]
		if !ok {
			return nil, false
		}
	}
	return cur, true
}

func prettyJSON(v any) string {
	b, err := json.MarshalIndent(v, "", "  ")
	if err != nil {
		return fmt.Sprint(v)
	}
	return string(b)
}

func truncateStr(s string, n int) string {
	if len(s) <= n {
		return s
	}
	return s[:n] + "…（截断）"
}

// authValue 解析 AuthRef：env:NAME 或 settings 点路径。
func authValue(ref string, settingsLookup func(key string) string) string {
	if strings.HasPrefix(ref, "env:") {
		return os.Getenv(strings.TrimPrefix(ref, "env:"))
	}
	if settingsLookup != nil {
		return settingsLookup(ref)
	}
	return ""
}