// Copyright 2026 Alibaba Group
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package helpers

import (
	"bufio"
	"context"
	"encoding/json"
	"fmt"
	"os/exec"
	"strings"
)

var connectStreamCommandContext = exec.CommandContext

// Incremental forwarding: channels whose CLI can emit stream-json get their
// reply streamed into the AI card as it is produced (the hermes/openclaw
// experience), instead of one shot at the end.
//
// Verified stdout protocols (run live against each CLI):
//   - "cc" (claude / codebuddy): JSONL; visible text arrives as
//     {"type":"stream_event","event":{"type":"content_block_delta",
//     "delta":{"type":"text_delta","text":"…"}}} (thinking_delta frames are
//     internal reasoning and are NOT shown); the final authoritative text is
//     {"type":"result","result":"…"}.
//   - "qoder" (qodercli): JSONL; per-turn snapshots arrive as
//     {"type":"assistant","message":{"content":[{"type":"text","text":"…"}]}}
//     and the final answer as {"type":"result","subtype":"success",
//     "message":{"content":[…]}}.

// canStream reports whether this forwarder has an incremental-output mode.
func (f *execForwarder) canStream() bool {
	return len(f.streamArgv) > 0 && f.parser != ""
}

// forwardStream runs the agent in incremental-output mode, calling onDelta
// with the full visible text so far whenever it grows, and returns the final
// reply. Falls back to the one-shot forward when streaming is unsupported.
func (f *execForwarder) forwardStream(ctx context.Context, convID, text string, onDelta func(string)) (string, error) {
	if !f.canStream() || onDelta == nil {
		return f.forward(ctx, convID, text)
	}
	ctx, cancel := applyTimeout(ctx, f.timeout)
	defer cancel()

	run := func() (string, string, error) {
		args := f.commandArgs(f.streamArgv, convID, text)
		cmd := connectStreamCommandContext(ctx, f.streamArgv[0], args...)
		f.configureCommand(cmd)
		stdout, err := cmd.StdoutPipe()
		if err != nil {
			return "", err.Error(), err
		}
		var stderrBuf strings.Builder
		cmd.Stderr = &stderrBuf
		if err := cmd.Start(); err != nil {
			return "", err.Error(), err
		}

		var acc strings.Builder // accumulated visible text ("cc" deltas / "qoder" turns)
		finalText := ""
		scanner := bufio.NewScanner(stdout)
		scanner.Buffer(make([]byte, 0, 64*1024), 4*1024*1024)
		for scanner.Scan() {
			line := strings.TrimSpace(scanner.Text())
			if line == "" || !strings.HasPrefix(line, "{") {
				continue
			}
			delta, final := parseStreamLine(f.parser, line)
			if delta != "" {
				acc.WriteString(delta)
				onDelta(brandReply(f.name, acc.String()))
			}
			if final != "" {
				finalText = final
			}
		}
		waitErr := cmd.Wait()

		if finalText == "" {
			finalText = strings.TrimSpace(acc.String())
		}
		// A bare backend error (e.g. claude's "API Error: 4xx ...") must not be
		// forwarded as the answer (issue #14): return an actionable hint instead.
		if agentReplyIsError(finalText) {
			if f.hasSession(convID) {
				f.sessions.reset(convID)
			}
			return agentBackendErrorReply(finalText), "", nil
		}
		if finalText != "" {
			return brandReply(f.name, finalText), "", nil
		}
		if waitErr != nil {
			msg := waitErr.Error()
			if s := strings.TrimSpace(stderrBuf.String()); s != "" {
				msg = s
			}
			return "", msg, waitErr
		}
		return "（本地 agent 无文本输出）", "", nil
	}

	reply, msg, err := run()
	if err == nil {
		return reply, nil
	}
	if f.hasSession(convID) && agentSessionMissingError(msg) {
		f.sessions.reset(convID)
		reply, msg, err = run()
		if err == nil {
			return reply, nil
		}
	}
	if f.hasSession(convID) {
		f.sessions.reset(convID)
	}
	return "", fmt.Errorf("本地 %s agent 调用失败：%s", f.name, truncateRunes(msg, 300))
}

// parseStreamLine extracts (visible-text delta, final text) from one JSONL
// line, per parser protocol. Either return value may be empty.
func parseStreamLine(parser, line string) (delta, final string) {
	switch parser {
	case "cc":
		var ev struct {
			Type  string `json:"type"`
			Event struct {
				Type  string `json:"type"`
				Delta struct {
					Type string `json:"type"`
					Text string `json:"text"`
				} `json:"delta"`
			} `json:"event"`
			Result string `json:"result"`
		}
		if json.Unmarshal([]byte(line), &ev) != nil {
			return "", ""
		}
		switch ev.Type {
		case "stream_event":
			if ev.Event.Type == "content_block_delta" && ev.Event.Delta.Type == "text_delta" {
				return ev.Event.Delta.Text, ""
			}
		case "result":
			return "", strings.TrimSpace(ev.Result)
		}
	case "qoder":
		var ev struct {
			Type    string `json:"type"`
			Subtype string `json:"subtype"`
			Result  string `json:"result"`
			Message struct {
				Content []struct {
					Type string `json:"type"`
					Text string `json:"text"`
				} `json:"content"`
			} `json:"message"`
		}
		if json.Unmarshal([]byte(line), &ev) != nil {
			return "", ""
		}
		text := func() string {
			var b strings.Builder
			for _, c := range ev.Message.Content {
				if c.Type == "text" {
					b.WriteString(c.Text)
				}
			}
			return strings.TrimSpace(b.String())
		}
		switch {
		case ev.Type == "result" && ev.Subtype == "success":
			if t := text(); t != "" {
				return "", t
			}
			return "", strings.TrimSpace(ev.Result)
		case ev.Type == "assistant":
			if t := text(); t != "" {
				// Turn-level snapshot: append as a paragraph.
				return t + "\n\n", ""
			}
		}
	}
	return "", ""
}