package swboot

import (
	"bytes"
	"context"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"time"

	"github.com/jackc/pgx/v5/pgxpool"
)

// ErrMergeRequiresSeparateAuthorization is a by-design boundary (design §10:
// approving execution never implies approving merge): the executor produces
// patch/test candidates only; merge/push/deploy always need a separate
// explicit authorization path and are never executed here.
var ErrMergeRequiresSeparateAuthorization = fmt.Errorf("ERR_MERGE_REQUIRES_SEPARATE_AUTHORIZATION: merge/push/deploy are never executed by the controlled patch executor; approve-execution does not imply merge")

// ControlledPatchRequest is one fail-closed execution unit.
type ControlledPatchRequest struct {
	ProjectID   int64
	RequestedBy int64
	RepoPath    string // absolute path of the bound repository
	BaseRef     string // explicit base commit-ish for the isolated worktree
	Patches     []string
	Commands    []string // must match admin-registered command prefixes
}

// ExecutionFile records one changed file with its content hash.
type ExecutionFile struct {
	Path string `json:"path"`
	Sha  string `json:"sha256"`
}

// ExecutionCommand records one allowlisted command run.
type ExecutionCommand struct {
	Command    string `json:"command"`
	ExitCode   int    `json:"exit_code"`
	DurationMs int64  `json:"duration_ms"`
	Output     string `json:"output,omitempty"`
	Truncated  bool   `json:"truncated,omitempty"`
}

// ControlledPatchResult is the evidence artifact of one execution.
type ControlledPatchResult struct {
	ID             int64              `json:"id"`
	ProjectID      int64              `json:"project_id"`
	Status         string             `json:"status"` // succeeded | failed
	RepoPath       string             `json:"repo_path"`
	BaseRef        string             `json:"base_ref"`
	Branch         string             `json:"branch"`
	WorktreePath   string             `json:"worktree_path"`
	PatchesApplied int                `json:"patches_applied"`
	Files          []ExecutionFile    `json:"files"`
	Commands       []ExecutionCommand `json:"commands"`
	Error          string             `json:"error,omitempty"`
}

// RepoAllowlistReader is the executor's view of the admin allowlist.
type RepoAllowlistReader interface {
	IsAllowlisted(absPath string) bool
	AllowedCommands(absPath string) []string
}

// ControlledPatchExecutor applies reviewed patches on an isolated git
// worktree and runs admin-allowlisted test commands. It never writes the
// repository working tree directly, never merges/pushes, stops on first
// failure without retry, and caps command time/output.
type ControlledPatchExecutor struct {
	Allowlist      RepoAllowlistReader
	Pool           *pgxpool.Pool // execution record persistence; nil = no persistence
	CommandAllow   func(cmd string) bool
	CommandTimeout time.Duration
	MaxOutputBytes int
	GitBin         string
}

const (
	defaultCommandTimeout = 10 * time.Minute
	defaultMaxOutputBytes = 1 << 20
	maxPatches            = 32
)

// Execute runs the fail-closed pipeline and persists the record.
func (e *ControlledPatchExecutor) Execute(ctx context.Context, req ControlledPatchRequest) (*ControlledPatchResult, error) {
	res := &ControlledPatchResult{
		ProjectID: req.ProjectID,
		RepoPath:  filepath.Clean(strings.TrimSpace(req.RepoPath)),
		BaseRef:   strings.TrimSpace(req.BaseRef),
		Status:    "failed",
	}
	fail := func(err error) (*ControlledPatchResult, error) {
		res.Error = err.Error()
		e.persist(ctx, req, res)
		return res, err
	}

	if e == nil || e.Allowlist == nil {
		return fail(fmt.Errorf("swboot: executor not configured"))
	}
	if !e.Allowlist.IsAllowlisted(res.RepoPath) {
		return fail(fmt.Errorf("%w: path %q not in admin allowlist", ErrRepoPathNotAllowlisted, res.RepoPath))
	}
	if res.BaseRef == "" {
		return fail(fmt.Errorf("swboot: base_ref required"))
	}
	if len(req.Patches) == 0 || len(req.Patches) > maxPatches {
		return fail(fmt.Errorf("swboot: 1..%d patches required", maxPatches))
	}
	gitBin := e.GitBin
	if gitBin == "" {
		gitBin = "git"
	}

	slug := fmt.Sprintf("swboot-p%d-%d", req.ProjectID, time.Now().UnixNano())
	branch := "feature/" + slug
	wtDir := filepath.Join(filepath.Dir(res.RepoPath), ".swboot-worktrees", slug)

	out, err := e.git(ctx, gitBin, res.RepoPath, "worktree", "add", "-b", branch, wtDir, res.BaseRef)
	if err != nil {
		return fail(fmt.Errorf("swboot: isolated worktree create failed: %v: %s", err, tail(out, 200)))
	}
	res.Branch = branch
	res.WorktreePath = wtDir
	// The worktree is evidence until separately cleaned; never auto-remove.

	for i, patch := range req.Patches {
		out, err := e.gitWithStdin(ctx, gitBin, wtDir, patch, "apply", "--check", "-")
		if err == nil {
			_, err = e.gitWithStdin(ctx, gitBin, wtDir, patch, "apply", "-")
		}
		if err != nil {
			return fail(fmt.Errorf("swboot: patch %d rejected: %v: %s", i+1, err, tail(out, 200)))
		}
		res.PatchesApplied = i + 1
	}

	files, err := changedFilesWithHashes(ctx, gitBin, wtDir)
	if err != nil {
		return fail(err)
	}
	res.Files = files

	allowedNames := e.Allowlist.AllowedCommands(res.RepoPath)
	for _, cmd := range req.Commands {
		if !commandAllowed(cmd, allowedNames) {
			return fail(fmt.Errorf("swboot: command not in admin allowlist: %.80s", cmd))
		}
		rec, err := e.runCommand(ctx, wtDir, cmd)
		res.Commands = append(res.Commands, rec)
		if err != nil {
			res.Error = fmt.Sprintf("command failed: %.200s", cmd)
			e.persist(ctx, req, res)
			return res, fmt.Errorf("swboot: %w", err)
		}
	}

	res.Status = "succeeded"
	e.persist(ctx, req, res)
	return res, nil
}

func (e *ControlledPatchExecutor) runCommand(ctx context.Context, dir, cmdLine string) (ExecutionCommand, error) {
	timeout := e.CommandTimeout
	if timeout <= 0 {
		timeout = defaultCommandTimeout
	}
	maxOut := e.MaxOutputBytes
	if maxOut <= 0 {
		maxOut = defaultMaxOutputBytes
	}
	rec := ExecutionCommand{Command: cmdLine}
	// FIND-SEC-03 回归：argv 化执行，不经 shell。命令行中的元字符
	//（;、&&、|、$() 等）只会成为 argv 参数，不会被求值。
	fields := strings.Fields(strings.TrimSpace(cmdLine))
	if len(fields) == 0 {
		return rec, fmt.Errorf("swboot: empty command")
	}
	cctx, cancel := context.WithTimeout(ctx, timeout)
	defer cancel()
	c := exec.CommandContext(cctx, fields[0], fields[1:]...)
	c.Dir = dir
	c.Env = []string{
		"PATH=" + os.Getenv("PATH"),
		"HOME=" + dir,
		"GIT_TERMINAL_PROMPT=0",
	}
	var buf bytes.Buffer
	c.Stdout = &limitedWriter{w: &buf, max: maxOut}
	c.Stderr = c.Stdout
	start := time.Now()
	err := c.Run()
	rec.DurationMs = time.Since(start).Milliseconds()
	rec.Output = tail(buf.String(), 4000)
	rec.Truncated = buf.Len() >= maxOut
	if ee, ok := err.(*exec.ExitError); ok {
		rec.ExitCode = ee.ExitCode()
	}
	if err != nil {
		if cctx.Err() == context.DeadlineExceeded {
			return rec, fmt.Errorf("command timed out after %s: %.80s", timeout, cmdLine)
		}
		return rec, fmt.Errorf("command exit: %v", err)
	}
	return rec, nil
}

type limitedWriter struct {
	w      *bytes.Buffer
	max    int
	exceed bool
}

func (l *limitedWriter) Write(p []byte) (int, error) {
	if l.w.Len()+len(p) > l.max {
		room := l.max - l.w.Len()
		if room > 0 {
			_, _ = l.w.Write(p[:room])
		}
		l.exceed = true
		return len(p), nil // swallow the rest
	}
	return l.w.Write(p)
}

func (e *ControlledPatchExecutor) git(ctx context.Context, bin, dir string, args ...string) (string, error) {
	return e.gitWithStdin(ctx, bin, dir, "", args...)
}

func (e *ControlledPatchExecutor) gitWithStdin(ctx context.Context, bin, dir, stdin string, args ...string) (string, error) {
	cctx, cancel := context.WithTimeout(ctx, 2*time.Minute)
	defer cancel()
	c := exec.CommandContext(cctx, bin, args...)
	c.Dir = dir
	c.Env = []string{"PATH=" + os.Getenv("PATH"), "GIT_TERMINAL_PROMPT=0"}
	if stdin != "" {
		c.Stdin = strings.NewReader(stdin)
	}
	var out bytes.Buffer
	c.Stdout, c.Stderr = &out, &out
	if err := c.Run(); err != nil {
		return out.String(), err
	}
	return out.String(), nil
}

func changedFilesWithHashes(ctx context.Context, gitBin, wtDir string) ([]ExecutionFile, error) {
	cctx, cancel := context.WithTimeout(ctx, 2*time.Minute)
	defer cancel()
	c := exec.CommandContext(cctx, gitBin, "status", "--porcelain")
	c.Dir = wtDir
	c.Env = []string{"PATH=" + os.Getenv("PATH"), "GIT_TERMINAL_PROMPT=0"}
	var out bytes.Buffer
	c.Stdout = &out
	if err := c.Run(); err != nil {
		return nil, fmt.Errorf("swboot: git status failed: %v", err)
	}
	var files []ExecutionFile
	for _, line := range strings.Split(out.String(), "\n") {
		if len(line) < 4 {
			continue
		}
		path := strings.TrimSpace(line[3:])
		if path == "" {
			continue
		}
		full := filepath.Join(wtDir, path)
		data, err := os.ReadFile(full)
		if err != nil {
			// Deleted or binary-unreadable entries still count as changed.
			files = append(files, ExecutionFile{Path: path})
			continue
		}
		sum := sha256.Sum256(data)
		files = append(files, ExecutionFile{Path: path, Sha: hex.EncodeToString(sum[:])})
	}
	return files, nil
}

func (e *ControlledPatchExecutor) persist(ctx context.Context, req ControlledPatchRequest, res *ControlledPatchResult) {
	if e == nil || e.Pool == nil || res == nil {
		return
	}
	filesJSON, _ := json.Marshal(res.Files)
	cmdsJSON, _ := json.Marshal(res.Commands)
	pctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()
	_ = req
	var id int64
	err := e.Pool.QueryRow(pctx, `
		INSERT INTO swboot_controlled_executions
			(project_id, requested_by, repo_path, base_ref, worktree_path, branch, status,
			 patches_applied, files_json, commands_json, error, started_at, finished_at)
		VALUES ($1,$2,$3,$4,$5,$6,$7,$8,$9,$10,$11,now(),now())
		RETURNING id
	`, res.ProjectID, req.RequestedBy, res.RepoPath, res.BaseRef, res.WorktreePath, res.Branch,
		res.Status, res.PatchesApplied, filesJSON, cmdsJSON, res.Error).Scan(&id)
	if err == nil {
		res.ID = id
	}
}

// commandAllowed 判定命令是否在 admin 登记的命令名白名单内。
// FIND-SEC-03 回归：只允许首段 basename 与白名单条目「精确相等」；
// 前缀匹配（go 放行 go-evil）与 shell 拼接均已移除。
func commandAllowed(cmd string, allowed []string) bool {
	fields := strings.Fields(strings.TrimSpace(cmd))
	if len(fields) == 0 {
		return false
	}
	seg := filepath.Base(fields[0])
	for _, p := range allowed {
		p = strings.TrimSpace(p)
		if p == "" {
			continue
		}
		if seg == p || seg == filepath.Base(p) {
			return true
		}
	}
	return false
}

func tail(s string, n int) string {
	s = strings.TrimSpace(s)
	if len(s) <= n {
		return s
	}
	return "..." + s[len(s)-n:]
}