package cc

import (
	"bufio"
	"bytes"
	"context"
	"encoding/json"
	"log/slog"
	"os/exec"
	"regexp"
	"time"
)

const reviewDefaultTimeoutMs = 300_000

// ReviewOpts configures a RunReview call.
type ReviewOpts struct {
	WorkspaceRoot string
	Prompt        string
	TimeoutMs     int // 0 → reviewDefaultTimeoutMs
	OnThreadID    func(string)
}

// RunCodex is the injectable runner. Tests replace this to avoid needing a real codex binary.
var RunCodex func(ctx context.Context, cwd string, args []string) (stdout, stderr []byte, err error) = defaultRunCodex

func defaultRunCodex(ctx context.Context, cwd string, args []string) ([]byte, []byte, error) {
	cmd := exec.CommandContext(ctx, "codex", args...)
	if cwd != "" {
		cmd.Dir = cwd
	}
	var stdout, stderr bytes.Buffer
	cmd.Stdout = &stdout
	cmd.Stderr = &stderr
	err := cmd.Run()
	return stdout.Bytes(), stderr.Bytes(), err
}

// RunReview runs `codex exec review --json` and calls opts.OnThreadID with the
// first thread_id/session_id found in the NDJSON output.
// Errors are logged, not returned (fire-and-forget semantics).
func RunReview(ctx context.Context, opts ReviewOpts) error {
	timeoutMs := opts.TimeoutMs
	if timeoutMs <= 0 {
		timeoutMs = reviewDefaultTimeoutMs
	}
	tCtx, cancel := context.WithTimeout(ctx, time.Duration(timeoutMs)*time.Millisecond)
	defer cancel()

	args := []string{
		"exec",
		"-c", "model_reasoning_effort=xhigh",
		"review",
		"--dangerously-bypass-approvals-and-sandbox",
		"--json",
		opts.Prompt,
	}

	stdout, stderr, err := RunCodex(tCtx, opts.WorkspaceRoot, args)
	if err != nil {
		slog.Warn("codex exec review failed", "err", err, "stderr", string(stderr))
		return nil // fire-and-forget: never propagate
	}

	if opts.OnThreadID != nil {
		scanForThreadID(stdout, opts.OnThreadID)
	}
	return nil
}

type threadEvent struct {
	ThreadID  string `json:"thread_id"`
	SessionID string `json:"session_id"`
	ID        string `json:"id"`
}

var uuidRe = regexp.MustCompile(`(?i)^[0-9a-f-]{16,}$`)

func scanForThreadID(ndjson []byte, onThreadID func(string)) {
	scanner := bufio.NewScanner(bytes.NewReader(ndjson))
	for scanner.Scan() {
		line := scanner.Bytes()
		if len(bytes.TrimSpace(line)) == 0 {
			continue
		}
		var ev threadEvent
		if err := json.Unmarshal(line, &ev); err != nil {
			continue
		}
		id := ""
		switch {
		case ev.ThreadID != "":
			id = ev.ThreadID
		case ev.SessionID != "":
			id = ev.SessionID
		case uuidRe.MatchString(ev.ID):
			id = ev.ID
		}
		if id != "" {
			onThreadID(id)
			return
		}
	}
}