package io

import (
	"context"
	"errors"
	"fmt"
	stdio "io"
	"io/fs"
	"log/slog"
	"os"
	"path/filepath"
	"strings"

	"git.yeij.top/AskaEth/Cyrene_v2/pkg/plugins/sdk"
)

// Compile-time assertion that fileTool implements sdk.Tool.
var _ sdk.Tool = (*fileTool)(nil)

// fileTool reads, writes, lists and searches files, confined to the configured
// data directory plus any explicit whitelist. Paths are cleaned and re-checked
// against those roots, so ".." traversal and symlink escapes are rejected.
//
// 本工具是文件访问沙箱的唯一实现处（裁决 13.4.4、design/04 §4）：roots 收敛、
// symlink 逃逸、NUL 字节与 ".." 穿越都在此判定，写入前先按真实落点校验父链。
type fileTool struct {
	roots    []string // absolute, cleaned allowed directories
	maxRead  int64
	maxWrite int64
	maxList  int
	log      *slog.Logger
}

func newFileTool(t *tools) *fileTool {
	roots := make([]string, 0, 1+len(t.fileWhitelist))
	if t.cfg != nil && t.cfg.DataDir != "" {
		roots = append(roots, absoluteClean(t.cfg.DataDir))
	}
	for _, w := range t.fileWhitelist {
		roots = append(roots, absoluteClean(w))
	}
	return &fileTool{
		roots:    roots,
		maxRead:  t.maxReadBytes,
		maxWrite: t.maxWriteBytes,
		maxList:  t.maxList,
		log:      t.log,
	}
}

// Name implements sdk.Tool.
func (f *fileTool) Name() string { return "file" }

// Description implements sdk.Tool.
func (f *fileTool) Description() string {
	return "Read, write, list or search files, restricted to the configured data directory and explicit whitelist."
}

// Parameters implements sdk.Tool.
func (f *fileTool) Parameters() (map[string]any, error) {
	return map[string]any{
		"type": "object",
		"properties": map[string]any{
			"action":  map[string]any{"type": "string", "enum": []any{actionRead, actionWrite, actionList, actionSearch}, "description": "Operation to perform."},
			"path":    map[string]any{"type": "string", "description": "Absolute or data-directory-relative file path."},
			"content": map[string]any{"type": "string", "description": "Body to write."},
			"query":   map[string]any{"type": "string", "description": "Substring filter for search."},
		},
		"required": []any{"action", "path"},
	}, nil
}

// Execute implements sdk.Tool.
func (f *fileTool) Execute(ctx context.Context, args any) (any, error) {
	m, ok := args.(map[string]any)
	if !ok {
		return nil, fmt.Errorf("io: file: args must be an object")
	}
	switch action := argString(m, "action"); action {
	case actionRead:
		return f.read(ctx, argString(m, "path"))
	case actionWrite:
		return f.write(ctx, argString(m, "path"), argString(m, "content"))
	case actionList:
		return f.list(ctx, argString(m, "path"))
	case actionSearch:
		return f.search(ctx, argString(m, "path"), argString(m, "query"))
	default:
		return nil, fmt.Errorf("io: file: unknown action %q", action)
	}
}

// read returns a file's content, capped at maxRead bytes.
func (f *fileTool) read(ctx context.Context, p string) (any, error) {
	if err := ctx.Err(); err != nil {
		return nil, err
	}
	real, err := f.resolveExisting(p)
	if err != nil {
		return nil, err
	}
	info, err := os.Stat(real)
	if err != nil {
		return nil, fmt.Errorf("io: file: stat: %w", err)
	}
	if info.IsDir() {
		return nil, fmt.Errorf("io: file: %q is a directory", real)
	}
	if info.Size() > f.maxRead {
		return nil, fmt.Errorf("io: file: %q exceeds the %d-byte read limit", real, f.maxRead)
	}
	fh, err := os.Open(real)
	if err != nil {
		return nil, fmt.Errorf("io: file: open: %w", err)
	}
	defer fh.Close()
	data, err := stdio.ReadAll(stdio.LimitReader(fh, f.maxRead+1))
	if err != nil {
		return nil, fmt.Errorf("io: file: read: %w", err)
	}
	if int64(len(data)) > f.maxRead {
		return nil, fmt.Errorf("io: file: %q exceeds the %d-byte read limit", real, f.maxRead)
	}
	return map[string]any{"path": real, "size": len(data), "content": string(data)}, nil
}

// write 创建或覆盖文件，内容上限 maxWrite 字节。流程：
//  1. 写入前先算出目标的真实落点，确认仍在 roots 内（防 roots 内的 symlink 逃逸）；
//  2. 建目录；
//  3. 建目录之后再核一遍父目录的真实落点——兜住建目录期间新出现的 symlink，以及
//     Windows 目录 junction 这类 filepath.EvalSymlinks 不解析的再解析点（此时解析
//     报错即拒），保证严格度不低于收敛前的实现（裁决 13.4.4）。
func (f *fileTool) write(ctx context.Context, p, content string) (any, error) {
	if err := ctx.Err(); err != nil {
		return nil, err
	}
	if int64(len(content)) > f.maxWrite {
		return nil, fmt.Errorf("io: file: content exceeds the %d-byte write limit", f.maxWrite)
	}
	target, err := f.resolveForCreate(p)
	if err != nil {
		return nil, err
	}
	parent := filepath.Dir(target)
	if err := os.MkdirAll(parent, dirPerm); err != nil {
		return nil, fmt.Errorf("io: file: mkdir: %w", err)
	}
	realParent, err := filepath.EvalSymlinks(parent)
	if err != nil {
		return nil, fmt.Errorf("io: file: resolve parent: %w", err)
	}
	if !f.withinReal(realParent) {
		f.log.Warn("io file: rejected write escaping allowed directories", "path", p, "resolved", realParent)
		return nil, fmt.Errorf("io: file: %q escapes the allowed directories", p)
	}
	if err := os.WriteFile(target, []byte(content), filePerm); err != nil {
		return nil, fmt.Errorf("io: file: write: %w", err)
	}
	return map[string]any{"path": target, "size": len(content)}, nil
}

// list returns the entries of a directory, capped at maxList.
func (f *fileTool) list(ctx context.Context, p string) (any, error) {
	if err := ctx.Err(); err != nil {
		return nil, err
	}
	real, err := f.resolveExisting(p)
	if err != nil {
		return nil, err
	}
	info, err := os.Stat(real)
	if err != nil {
		return nil, fmt.Errorf("io: file: stat: %w", err)
	}
	if !info.IsDir() {
		return nil, fmt.Errorf("io: file: %q is not a directory", real)
	}
	entries, err := os.ReadDir(real)
	if err != nil {
		return nil, fmt.Errorf("io: file: readdir: %w", err)
	}
	if len(entries) > f.maxList {
		entries = entries[:f.maxList]
	}
	out := make([]map[string]any, 0, len(entries))
	for _, e := range entries {
		ei, err := e.Info()
		if err != nil {
			continue
		}
		out = append(out, map[string]any{"name": e.Name(), "size": ei.Size(), "dir": ei.IsDir()})
	}
	return map[string]any{"path": real, "entries": out, "count": len(out)}, nil
}

// search walks a base directory (default the primary root) and returns files
// whose names contain query, capped at maxList results.
func (f *fileTool) search(ctx context.Context, base, query string) (any, error) {
	if err := ctx.Err(); err != nil {
		return nil, err
	}
	if strings.TrimSpace(query) == "" {
		return nil, fmt.Errorf("io: file: search query is required")
	}
	base, err := f.searchBase(base)
	if err != nil {
		return nil, err
	}
	real, err := f.resolveExisting(base)
	if err != nil {
		return nil, err
	}
	info, err := os.Stat(real)
	if err != nil {
		return nil, fmt.Errorf("io: file: stat: %w", err)
	}
	if !info.IsDir() {
		return nil, fmt.Errorf("io: file: %q is not a directory", real)
	}
	q := strings.ToLower(query)
	hits := make([]map[string]any, 0)
	walkErr := filepath.WalkDir(real, func(pp string, d fs.DirEntry, err error) error {
		if err != nil || d.IsDir() {
			return nil
		}
		if !strings.Contains(strings.ToLower(d.Name()), q) {
			return nil
		}
		di, err := d.Info()
		if err != nil {
			return nil
		}
		rel, rerr := filepath.Rel(real, pp)
		if rerr != nil {
			rel = pp
		}
		hits = append(hits, map[string]any{"path": rel, "size": di.Size()})
		if len(hits) >= f.maxList {
			return fs.SkipAll
		}
		return nil
	})
	if walkErr != nil && !errors.Is(walkErr, fs.SkipAll) {
		return nil, fmt.Errorf("io: file: walk: %w", walkErr)
	}
	return map[string]any{"base": real, "query": query, "hits": hits, "count": len(hits)}, nil
}

// searchBase 解析 search 的基准目录：显式给定就原样返回（由 resolveExisting 归一），
// 缺省时用主 root。执行路径与目标声明（file_targets.go 的 declaredPath）必须用同一
// 份缺省口径，否则声明出来的路径会与真正走查的目录不是同一个。
func (f *fileTool) searchBase(base string) (string, error) {
	if strings.TrimSpace(base) != "" {
		return base, nil
	}
	if len(f.roots) == 0 {
		return "", fmt.Errorf("io: file: no base directory configured")
	}
	return f.roots[0], nil
}

// ErrNullByte 表示路径中含 NUL 字节：在触达文件系统之前就被拒绝（收敛自原 exec 文件
// 沙箱，裁决 13.4.4）。调用方与测试一律用 errors.Is(err, ErrNullByte) 判定——不要断言
// 错误文本；此处只存不带来源前缀的文本，前缀由返回值处的 fmt.Errorf 补上，保证对外错误
// 文本与收敛前逐字节一致。
var ErrNullByte = errors.New("path contains a NUL byte")

// resolve 清洗路径并确认其词法上留在允许的 roots 之内：拒绝空路径与含 NUL 字节的
// 路径（NUL 收敛自原 exec 文件沙箱，裁决 13.4.4），拒绝 ".." 穿越与越界的绝对路径；
// 返回绝对、clean 的词法路径。
func (f *fileTool) resolve(p string) (string, error) {
	if strings.TrimSpace(p) == "" {
		return "", fmt.Errorf("io: file: path is required")
	}
	if strings.IndexByte(p, 0) >= 0 {
		return "", fmt.Errorf("io: file: %w", ErrNullByte)
	}
	if len(f.roots) == 0 {
		return "", fmt.Errorf("io: file: no base directory configured")
	}
	clean := filepath.Clean(p)
	if !filepath.IsAbs(clean) {
		clean = filepath.Join(f.roots[0], clean)
	}
	clean = filepath.Clean(clean)
	if !f.within(clean) {
		return "", fmt.Errorf("io: file: %q is outside the allowed directories", p)
	}
	return clean, nil
}

// resolveExisting 解析一个必须已存在的路径：要求其 symlink 解析后的真实落点仍在
// roots 的真实路径之内，防住经由 roots 内 symlink 的逃逸。目标不存在时报错。
func (f *fileTool) resolveExisting(p string) (string, error) {
	clean, err := f.resolve(p)
	if err != nil {
		return "", err
	}
	real, err := filepath.EvalSymlinks(clean)
	if err != nil {
		return "", fmt.Errorf("io: file: resolve %q: %w", p, err)
	}
	if !f.withinReal(real) {
		f.log.Warn("io file: rejected path escaping allowed directories", "path", p, "resolved", real)
		return "", fmt.Errorf("io: file: %q escapes the allowed directories", p)
	}
	return real, nil
}

// resolveForCreate 解析一个可能尚不存在（即将创建）的写入目标：先推出最深存在祖先
// 的真实落点，确认仍在 roots 内后返回真实路径（真实祖先 + 尚未创建的分量）。
func (f *fileTool) resolveForCreate(p string) (string, error) {
	clean, err := f.resolve(p)
	if err != nil {
		return "", err
	}
	real, err := resolveReal(clean)
	if err != nil {
		return "", fmt.Errorf("io: file: resolve %q: %w", p, err)
	}
	if !f.withinReal(real) {
		f.log.Warn("io file: rejected write escaping allowed directories", "path", p, "resolved", real)
		return "", fmt.Errorf("io: file: %q escapes the allowed directories", p)
	}
	return real, nil
}

// within 报告 p 是否词法上位于（或等于）某个 root 之内。
func (f *fileTool) within(p string) bool { return withinRoots(p, f.roots) }

// withinReal 报告真实落点 p 是否位于某个 root 的真实路径之内。
func (f *fileTool) withinReal(p string) bool { return withinRoots(p, f.realRoots()) }

// realRoots 返回各 root 的真实路径：存在则解析 symlink，尚未创建则按最深存在祖先
// 推导。把「真实落点」与 roots 放进同一（真实）路径空间比较，既拦得住 roots 内
// symlink 的逃逸，也不会把「DataDir 自身是 symlink」的正常部署误判为逃逸。
func (f *fileTool) realRoots() []string {
	out := make([]string, 0, len(f.roots))
	for _, r := range f.roots {
		real, err := resolveReal(r)
		if err != nil {
			real = r
		}
		out = append(out, real)
	}
	return out
}

// withinRoots 报告 p 是否位于（或等于）roots 中的某一个之内：按 filepath.Rel 判定，
// 相对路径为 "." 或不以 ".." 开头即为包含。
func withinRoots(p string, roots []string) bool {
	for _, root := range roots {
		rel, err := filepath.Rel(root, p)
		if err != nil {
			continue
		}
		if rel == "." || (rel != ".." && !strings.HasPrefix(rel, ".."+string(filepath.Separator))) {
			return true
		}
	}
	return false
}

// resolveReal 返回 p 的真实（symlink 解析后）路径：p 自身存在时直接解析；不存在时
// 沿父级上溯到最深的存在祖先，再把尚未创建的分量拼回。这样「即将创建」的路径也能
// 在落盘前判定真实落点，避免 MkdirAll 沿 roots 内的 symlink 逃逸。
func resolveReal(p string) (string, error) {
	cur := filepath.Clean(p)
	remaining := ""
	for {
		if real, err := filepath.EvalSymlinks(cur); err == nil {
			if remaining == "" {
				return real, nil
			}
			return filepath.Join(real, remaining), nil
		}
		base := filepath.Base(cur)
		parent := filepath.Dir(cur)
		if parent == cur {
			return "", fmt.Errorf("no existing ancestor for %s", p)
		}
		if remaining == "" {
			remaining = base
		} else {
			remaining = filepath.Join(base, remaining)
		}
		cur = parent
	}
}

// absoluteClean absolutizes and cleans p, returning the best-effort absolute
// form used as an allowed root.
func absoluteClean(p string) string {
	a, err := filepath.Abs(p)
	if err != nil {
		return filepath.Clean(p)
	}
	return filepath.Clean(a)
}