package tools

import (
	"context"
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"regexp"
	"strings"

	"agent-native/runtime/filestate"
)

type readFile struct {
	root  string
	files *filestate.Tracker
}

func (t *readFile) Name() string   { return "read_file" }
func (t *readFile) Replay() string { return ReplaySafe }
func (t *readFile) Description() string {
	return "Read a UTF-8 text file inside the workspace. Without offset/limit returns the whole file (truncated at 200 KiB); with offset/limit returns numbered lines from a 1-based offset."
}
func (t *readFile) Parameters() json.RawMessage {
	return json.RawMessage(`{"type":"object","required":["path"],"properties":{"path":{"type":"string"},"offset":{"type":"integer","description":"1-based first line to return"},"limit":{"type":"integer","description":"number of lines to return"}}}`)
}
func (t *readFile) Execute(_ context.Context, args json.RawMessage) (Result, error) {
	var obj struct {
		Path   string `json:"path"`
		Offset int    `json:"offset"`
		Limit  int    `json:"limit"`
	}
	if err := json.Unmarshal(args, &obj); err != nil {
		return Result{}, err
	}
	path, err := mustPath(t.root, obj.Path)
	if err != nil {
		return Result{Content: err.Error(), IsError: true}, nil
	}
	b, err := os.ReadFile(path)
	if err != nil {
		return Result{Content: err.Error(), IsError: true}, nil
	}
	if obj.Offset <= 0 && obj.Limit <= 0 {
		truncated := false
		if len(b) > maxReadBytes {
			b = []byte(CutUTF8(string(b), maxReadBytes))
			truncated = true
		}
		content := string(b)
		if truncated {
			content += "\n[truncated at 200 KiB; use offset/limit to page through the file]"
		}
		_ = t.files.NoteRead(path)
		return Result{Content: content}, nil
	}
	if obj.Offset <= 0 {
		obj.Offset = 1
	}
	if obj.Limit <= 0 {
		obj.Limit = 1000
	}
	lines := strings.Split(string(b), "\n")
	if obj.Offset > len(lines) {
		return Result{Content: fmt.Sprintf("offset %d beyond end of file (%d lines)", obj.Offset, len(lines)), IsError: true}, nil
	}
	end := obj.Offset - 1 + obj.Limit
	if end > len(lines) {
		end = len(lines)
	}
	var out []string
	for i := obj.Offset - 1; i < end; i++ {
		out = append(out, fmt.Sprintf("%d\t%s", i+1, lines[i]))
	}
	_ = t.files.NoteRead(path)
	return Result{Content: strings.Join(out, "\n")}, nil
}

type writeFile struct {
	root     string
	files    *filestate.Tracker
	mark     func(rel string, before []byte, existed bool, after []byte)
	writable []string // empty = unrestricted (product default)
}

func (t *writeFile) Name() string { return "write_file" }
func (t *writeFile) Description() string {
	return "Create or replace a UTF-8 text file inside the workspace."
}
func (t *writeFile) Parameters() json.RawMessage {
	return json.RawMessage(`{"type":"object","required":["path","content"],"properties":{"path":{"type":"string"},"content":{"type":"string"}}}`)
}
func (t *writeFile) Execute(_ context.Context, args json.RawMessage) (Result, error) {
	var obj struct {
		Path    string `json:"path"`
		Content string `json:"content"`
	}
	if err := json.Unmarshal(args, &obj); err != nil {
		return Result{}, err
	}
	path, err := mustPath(t.root, obj.Path)
	if err != nil {
		return Result{Content: err.Error(), IsError: true}, nil
	}
	if msg := rejectOutsideWriteSet(t.writable, obj.Path); msg != "" {
		return Result{Content: msg, IsError: true}, nil
	}
	if msg := rejectStaleWrite(t.files, path); msg != "" {
		return Result{Content: msg, IsError: true}, nil
	}
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		return Result{Content: err.Error(), IsError: true}, nil
	}
	before, existed := fileBefore(path)
	if err := atomicWriteFile(path, []byte(obj.Content), 0o644); err != nil {
		return Result{Content: err.Error(), IsError: true}, nil
	}
	if t.mark != nil {
		t.mark(obj.Path, before, existed, []byte(obj.Content))
	}
	return Result{Content: "wrote " + obj.Path}, nil
}

type editFile struct {
	root     string
	files    *filestate.Tracker
	mark     func(rel string, before []byte, existed bool, after []byte)
	writable []string
}

func (t *editFile) Name() string { return "edit_file" }
func (t *editFile) Description() string {
	return "Replace one unique exact text span in a workspace file."
}
func (t *editFile) Parameters() json.RawMessage {
	return json.RawMessage(`{"type":"object","required":["path","old","new"],"properties":{"path":{"type":"string"},"old":{"type":"string"},"new":{"type":"string"}}}`)
}
func (t *editFile) Execute(_ context.Context, args json.RawMessage) (Result, error) {
	var obj struct {
		Path string `json:"path"`
		Old  string `json:"old"`
		New  string `json:"new"`
	}
	if err := json.Unmarshal(args, &obj); err != nil {
		return Result{}, err
	}
	if obj.Old == "" {
		return Result{Content: "old text is empty", IsError: true}, nil
	}
	path, err := mustPath(t.root, obj.Path)
	if err != nil {
		return Result{Content: err.Error(), IsError: true}, nil
	}
	if msg := rejectOutsideWriteSet(t.writable, obj.Path); msg != "" {
		return Result{Content: msg, IsError: true}, nil
	}
	if msg := rejectStaleWrite(t.files, path); msg != "" {
		return Result{Content: msg, IsError: true}, nil
	}
	b, err := os.ReadFile(path)
	if err != nil {
		return Result{Content: err.Error(), IsError: true}, nil
	}
	text := string(b)
	n := strings.Count(text, obj.Old)
	if n != 1 {
		return Result{Content: fmt.Sprintf("expected one match, found %d", n), IsError: true}, nil
	}
	updated := strings.Replace(text, obj.Old, obj.New, 1)
	if err := atomicWriteFile(path, []byte(updated), 0o644); err != nil {
		return Result{Content: err.Error(), IsError: true}, nil
	}
	if t.mark != nil {
		t.mark(obj.Path, b, true, []byte(updated))
	}
	return Result{Content: "edited " + obj.Path}, nil
}

type listDir struct{ root string }

func (t *listDir) Name() string   { return "list_dir" }
func (t *listDir) Replay() string { return ReplaySafe }
func (t *listDir) Description() string {
	return "List names in a workspace directory."
}
func (t *listDir) Parameters() json.RawMessage {
	return json.RawMessage(`{"type":"object","properties":{"path":{"type":"string"}}}`)
}
func (t *listDir) Execute(_ context.Context, args json.RawMessage) (Result, error) {
	rel, _ := readArg(args, "path")
	if rel == "" {
		rel = "."
	}
	path, err := mustPath(t.root, rel)
	if err != nil {
		return Result{Content: err.Error(), IsError: true}, nil
	}
	entries, err := os.ReadDir(path)
	if err != nil {
		return Result{Content: err.Error(), IsError: true}, nil
	}
	names := make([]string, 0, len(entries))
	for _, e := range entries {
		name := e.Name()
		if e.IsDir() {
			name += "/"
		}
		names = append(names, name)
	}
	return Result{Content: strings.Join(names, "\n")}, nil
}

type grepTool struct{ root string }

func (t *grepTool) Name() string   { return "grep" }
func (t *grepTool) Replay() string { return ReplaySafe }
func (t *grepTool) Description() string {
	return "Search workspace text files. Literal substring by default; regex=true switches to Go regexp, include filters file names (e.g. *.go), ignore_case folds case. Caps at 50 hits."
}
func (t *grepTool) Parameters() json.RawMessage {
	return json.RawMessage(`{"type":"object","required":["pattern"],"properties":{"pattern":{"type":"string"},"path":{"type":"string"},"regex":{"type":"boolean"},"ignore_case":{"type":"boolean"},"include":{"type":"string","description":"file-name glob filter such as *.go"}}}`)
}
func (t *grepTool) Execute(_ context.Context, args json.RawMessage) (Result, error) {
	var obj struct {
		Pattern    string `json:"pattern"`
		Path       string `json:"path"`
		Regex      bool   `json:"regex"`
		IgnoreCase bool   `json:"ignore_case"`
		Include    string `json:"include"`
	}
	if err := json.Unmarshal(args, &obj); err != nil {
		return Result{}, err
	}
	if strings.TrimSpace(obj.Pattern) == "" {
		return Result{Content: "pattern is empty", IsError: true}, nil
	}
	if obj.Path == "" {
		obj.Path = "."
	}
	var includeRe *globMatcher
	if strings.TrimSpace(obj.Include) != "" {
		m, err := newGlobMatcher(obj.Include)
		if err != nil {
			return Result{Content: err.Error(), IsError: true}, nil
		}
		includeRe = m
	}
	contains := func(line string) bool { return strings.Contains(line, obj.Pattern) }
	if obj.Regex {
		pat := obj.Pattern
		if obj.IgnoreCase {
			pat = "(?i)" + pat
		}
		re, cerr := regexp.Compile(pat)
		if cerr != nil {
			return Result{Content: cerr.Error(), IsError: true}, nil
		}
		contains = re.MatchString
	} else if obj.IgnoreCase {
		lower := strings.ToLower(obj.Pattern)
		contains = func(line string) bool { return strings.Contains(strings.ToLower(line), lower) }
	}
	start, err := mustPath(t.root, obj.Path)
	if err != nil {
		return Result{Content: err.Error(), IsError: true}, nil
	}
	var hits []string
	err = filepath.WalkDir(start, func(path string, d os.DirEntry, walkErr error) error {
		if walkErr != nil || d.IsDir() {
			return nil
		}
		if len(hits) >= 50 {
			return fmt.Errorf("stop")
		}
		if includeRe != nil && !includeRe.Match(filepath.Base(path)) {
			return nil
		}
		b, err := os.ReadFile(path)
		if err != nil || len(b) > maxReadBytes {
			return nil
		}
		rel, _ := filepath.Rel(t.root, path)
		for i, line := range strings.Split(string(b), "\n") {
			if contains(line) {
				hits = append(hits, fmt.Sprintf("%s:%d:%s", filepath.ToSlash(rel), i+1, line))
				if len(hits) >= 50 {
					return fmt.Errorf("stop")
				}
			}
		}
		return nil
	})
	if err != nil && err.Error() != "stop" {
		return Result{Content: err.Error(), IsError: true}, nil
	}
	if len(hits) == 0 {
		return Result{Content: "no matches"}, nil
	}
	return Result{Content: strings.Join(hits, "\n")}, nil
}

// multiEditTool 一次多处替换：全部命中且互不冲突才落盘，任一失败即整体不动。
type multiEditTool struct {
	root     string
	files    *filestate.Tracker
	mark     func(rel string, before []byte, existed bool, after []byte)
	writable []string
}

func (t *multiEditTool) Name() string { return "multi_edit" }
func (t *multiEditTool) Description() string {
	return "Apply several unique-span replacements to one workspace file atomically: either all edits land or the file is left untouched."
}
func (t *multiEditTool) Parameters() json.RawMessage {
	return json.RawMessage(`{"type":"object","required":["path","edits"],"properties":{"path":{"type":"string"},"edits":{"type":"array","items":{"type":"object","required":["old","new"],"properties":{"old":{"type":"string"},"new":{"type":"string"}}}}}}`)
}

type multiEditSpan struct {
	Old string `json:"old"`
	New string `json:"new"`
}

func (t *multiEditTool) Execute(_ context.Context, args json.RawMessage) (Result, error) {
	var obj struct {
		Path  string          `json:"path"`
		Edits []multiEditSpan `json:"edits"`
	}
	if err := json.Unmarshal(args, &obj); err != nil {
		return Result{}, err
	}
	if len(obj.Edits) == 0 {
		return Result{Content: "edits is empty", IsError: true}, nil
	}
	path, err := mustPath(t.root, obj.Path)
	if err != nil {
		return Result{Content: err.Error(), IsError: true}, nil
	}
	if msg := rejectOutsideWriteSet(t.writable, obj.Path); msg != "" {
		return Result{Content: msg, IsError: true}, nil
	}
	if msg := rejectStaleWrite(t.files, path); msg != "" {
		return Result{Content: msg, IsError: true}, nil
	}
	b, err := os.ReadFile(path)
	if err != nil {
		return Result{Content: err.Error(), IsError: true}, nil
	}
	text := string(b)
	for i, e := range obj.Edits {
		if e.Old == "" {
			return Result{Content: fmt.Sprintf("edit %d: old text is empty", i+1), IsError: true}, nil
		}
		n := strings.Count(text, e.Old)
		if n != 1 {
			return Result{Content: fmt.Sprintf("edit %d: expected one match, found %d; file unchanged", i+1, n), IsError: true}, nil
		}
		text = strings.Replace(text, e.Old, e.New, 1)
	}
	if err := atomicWriteFile(path, []byte(text), 0o644); err != nil {
		return Result{Content: err.Error(), IsError: true}, nil
	}
	if t.mark != nil {
		t.mark(obj.Path, b, true, []byte(text))
	}
	return Result{Content: fmt.Sprintf("applied %d edits to %s", len(obj.Edits), obj.Path)}, nil
}

func fileBefore(path string) ([]byte, bool) {
	b, err := os.ReadFile(path)
	if err != nil {
		return nil, false
	}
	return b, true
}