package runner

import (
	"bytes"
	"context"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"time"

	"gitea-codex-bot/internal/config"
	"gitea-codex-bot/internal/domain"
	"gitea-codex-bot/internal/review"
)

const startMarker = "__CODEX_REVIEW_RESULT_BEGIN__"
const endMarker = "__CODEX_REVIEW_RESULT_END__"
const maxRunnerOutput = 4 << 20

type DockerRunner struct{ settings config.Settings }

func NewDockerRunner(settings config.Settings) *DockerRunner {
	return &DockerRunner{settings: settings}
}

func (r *DockerRunner) Run(parent context.Context, pr domain.PullRequestContext, cmd domain.ParsedCommand, cfg domain.RepoReviewConfig) (domain.ReviewResult, error) {
	ctx, cancel := context.WithTimeout(parent, time.Duration(r.settings.MaxReviewMinutes)*time.Minute)
	defer cancel()
	nonce := fmt.Sprintf("%d", time.Now().UnixNano())
	begin, end := startMarker+"_"+nonce, endMarker+"_"+nonce
	prompt := review.BuildPrompt(cmd, cfg, pr)
	script := r.script(pr, prompt, begin, end)
	name := "codex-review-" + nonce
	args := []string{"run", "--rm", "-i", "--name", name, "--cap-drop=ALL", "--security-opt", "no-new-privileges", "--read-only", "--tmpfs", "/tmp:rw,noexec,nosuid,size=512m", "--tmpfs", "/work:rw,nosuid,size=1g", "-e", "CODEX_DISABLE_TELEMETRY=1"}
	if r.settings.CodexAuthMode == "chatgpt" {
		args = append(args, "-e", "CODEX_AUTH_JSON_B64")
	} else {
		args = append(args, "-e", "OPENAI_API_KEY")
	}
	args = append(args, "-e", "GITEA_TOKEN", "-e", "GITEA_GIT_USERNAME", r.settings.RunnerImage, "bash", "-lc", script)
	cmdExec := exec.CommandContext(ctx, "docker", args...)
	cmdExec.Env = append(os.Environ(), "OPENAI_API_KEY="+r.settings.OpenAIAPIKey, "GITEA_TOKEN="+r.settings.GiteaToken, "GITEA_GIT_USERNAME="+r.settings.GiteaBotUsername)
	if r.settings.CodexAuthMode == "chatgpt" {
		data, err := readAuthJSON(r.settings.CodexAuthJSONPath)
		if err != nil {
			return domain.ReviewResult{}, err
		}
		cmdExec.Env = append(cmdExec.Env, "CODEX_AUTH_JSON_B64="+base64.StdEncoding.EncodeToString(data))
	}
	var output limitedBuffer
	output.limit = maxRunnerOutput
	cmdExec.Stdout = &output
	cmdExec.Stderr = &output
	if err := cmdExec.Run(); err != nil {
		_ = exec.CommandContext(context.Background(), "docker", "rm", "-f", name).Run()
		if ctx.Err() != nil {
			return domain.ReviewResult{}, fmt.Errorf("review runner timeout: %w", ctx.Err())
		}
		return domain.ReviewResult{}, fmt.Errorf("review runner failed: %w", err)
	}
	text := output.String()
	start := strings.Index(text, begin)
	endPos := strings.LastIndex(text, end)
	if start < 0 || endPos <= start {
		return domain.ReviewResult{}, fmt.Errorf("review runner returned no result artifact")
	}
	artifact := strings.TrimSpace(text[start+len(begin) : endPos])
	var result domain.ReviewResult
	if err := json.Unmarshal([]byte(artifact), &result); err != nil {
		return domain.ReviewResult{}, err
	}
	if err := review.ValidateResult(result); err != nil {
		return domain.ReviewResult{}, err
	}
	return result, nil
}

func readAuthJSON(rawPath string) ([]byte, error) {
	path := os.ExpandEnv(rawPath)
	if strings.HasPrefix(path, "~/") {
		home, err := os.UserHomeDir()
		if err != nil {
			return nil, err
		}
		path = filepath.Join(home, strings.TrimPrefix(path, "~/"))
	}
	data, err := os.ReadFile(filepath.Clean(path))
	if err != nil {
		return nil, err
	}
	if !json.Valid(data) {
		return nil, fmt.Errorf("CODEX_AUTH_JSON_PATH is not valid JSON")
	}
	return data, nil
}

func (r *DockerRunner) script(pr domain.PullRequestContext, prompt, begin, end string) string {
	auth := base64.StdEncoding.EncodeToString([]byte(r.settings.GiteaBotUsername + ":" + r.settings.GiteaToken))
	schema := `{"type":"object","additionalProperties":false,"required":["verdict","confidence","summary","findings","markdown_comment"],"properties":{"verdict":{"type":"string","enum":["correct","has_issues"]},"confidence":{"type":"number"},"summary":{"type":"string"},"markdown_comment":{"type":"string"},"findings":{"type":"array"}}}`
	quote := func(value string) string { return "'" + strings.ReplaceAll(value, "'", "'\"'\"'") + "'" }
	baseRemote := "origin"
	remoteSetup := ""
	if pr.BaseCloneURL != "" && pr.BaseCloneURL != pr.CloneURL {
		baseRemote = "upstream"
		remoteSetup = "git remote add upstream " + quote(pr.BaseCloneURL)
	}
	authSetup := ""
	if r.settings.CodexAuthMode == "chatgpt" {
		authSetup = "mkdir -p /root/.codex; printf '%s' \"$CODEX_AUTH_JSON_B64\" | base64 -d > /root/.codex/auth.json; chmod 600 /root/.codex/auth.json"
	}
	fetchHead := "git -c http.extraHeader=" + quote("Authorization: Basic "+auth) + " fetch --no-tags origin " + quote(pr.HeadRef) + " || git -c http.extraHeader=" + quote("Authorization: Basic "+auth) + " fetch --no-tags origin " + quote(pr.HeadSHA)
	fetchBase := "git -c http.extraHeader=" + quote("Authorization: Basic "+auth) + " fetch --no-tags " + baseRemote + " " + quote(pr.BaseRef) + " || git -c http.extraHeader=" + quote("Authorization: Basic "+auth) + " fetch --no-tags " + baseRemote + " " + quote(pr.BaseSHA)
	steps := []string{"set -eu", "printf '%s' " + quote(schema) + " > /tmp/schema.json"}
	if authSetup != "" {
		steps = append(steps, authSetup)
	}
	steps = append(steps, "git -c http.extraHeader="+quote("Authorization: Basic "+auth)+" clone --no-tags --depth 80 "+quote(pr.CloneURL)+" /work/repo", "cd /work/repo")
	if remoteSetup != "" {
		steps = append(steps, remoteSetup)
	}
	steps = append(steps, fetchHead, fetchBase, "git checkout --detach "+quote(pr.HeadSHA), "test \"$(git rev-parse HEAD)\" = "+quote(pr.HeadSHA), "unset GITEA_TOKEN", "codex exec --sandbox danger-full-access --json --output-schema /tmp/schema.json -o /tmp/result.json -m "+quote(r.settings.OpenAIReviewModel)+" "+quote(prompt), "test -s /tmp/result.json", "printf '%s\\n' "+quote(begin), "cat /tmp/result.json", "printf '%s\\n' "+quote(end))
	return strings.Join(steps, "; ")
}

type limitedBuffer struct {
	buffer    bytes.Buffer
	limit     int
	truncated bool
}

func (b *limitedBuffer) Write(p []byte) (int, error) {
	remaining := b.limit - b.buffer.Len()
	if remaining <= 0 {
		b.truncated = true
		return len(p), nil
	}
	if len(p) > remaining {
		_, _ = b.buffer.Write(p[:remaining])
		b.truncated = true
		return len(p), nil
	}
	return b.buffer.Write(p)
}
func (b *limitedBuffer) String() string { return b.buffer.String() }

var _ domain.ReviewRunner = (*DockerRunner)(nil)