package tools

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io/fs"
	"os"
	"path/filepath"
	"strings"

	"agentu/pkg/llm"
)

const defaultOutlineMaxFiles = 200

// ────────────────────────────────────────────────────────────────────────────
// ProjectOutlineTool — gitignore-aware file tree + symbol outline
// ────────────────────────────────────────────────────────────────────────────

type ProjectOutlineTool struct {
	workingDir string
}

func NewProjectOutlineTool(workingDir string) *ProjectOutlineTool {
	return &ProjectOutlineTool{workingDir: workingDir}
}

func (t *ProjectOutlineTool) Definition() llm.Tool {
	return llm.Tool{
		Type: "function",
		Function: llm.ToolFunction{
			Name:        "project_outline",
			Description: "Get the project file tree and code symbol outline in one call. Respects .gitignore. Use this first to understand project structure before reading individual files.",
			Parameters: JSONSchema(`{
  "type": "object",
  "properties": {
    "path": {"type": "string", "description": "Subdirectory to outline. Defaults to the project root."},
    "max_files": {"type": "integer", "description": "Maximum files to include in the outline. Defaults to 200."}
  },
  "additionalProperties": false
}`),
		},
	}
}

type outlineArgs struct {
	Path     string `json:"path"`
	MaxFiles int    `json:"max_files"`
}

func (t *ProjectOutlineTool) Execute(ctx context.Context, raw json.RawMessage) (string, error) {
	var args outlineArgs
	if err := json.Unmarshal(raw, &args); err != nil {
		return "", fmt.Errorf("parse arguments: %w", err)
	}

	root, err := resolvePath(t.workingDir, args.Path)
	if err != nil {
		return "", err
	}

	limit := args.MaxFiles
	if limit <= 0 {
		limit = defaultOutlineMaxFiles
	}

	// Parse .gitignore files from the root upward.
	ignorer := newGitignoreMatcher(root)

	var out strings.Builder
	out.WriteString(root)
	out.WriteString("\n")

	count := 0
	truncated := false

	err = filepath.WalkDir(root, func(path string, d fs.DirEntry, err error) error {
		if err != nil {
			return nil
		}
		if ctx.Err() != nil {
			return ctx.Err()
		}

		// Skip always-ignored directories.
		if d.IsDir() {
			name := d.Name()
			// Always skip VCS and common build-artifact directories.
			switch name {
			case ".git", ".hg", ".svn", "vendor", "node_modules",
				"dist", "build", "__pycache__", "target":
				return filepath.SkipDir
			}
			// Skip hidden directories other than .github and similar.
			if strings.HasPrefix(name, ".") && name != ".github" && name != ".vscode" && name != ".devcontainer" {
				return filepath.SkipDir
			}
		}

		rel, _ := filepath.Rel(root, path)
		if rel == "." {
			return nil
		}

		// Check gitignore.
		if ignorer.shouldIgnore(rel, d.IsDir()) {
			if d.IsDir() {
				return filepath.SkipDir
			}
			return nil
		}

		if count >= limit {
			truncated = true
			return filepath.SkipAll
		}

		// Build indented tree entry.
		depth := strings.Count(rel, string(filepath.Separator))
		indent := strings.Repeat("  ", depth)
		name := d.Name()

		if d.IsDir() {
			out.WriteString(fmt.Sprintf("%s%s/\n", indent, name))
			return nil
		}

		count++
		out.WriteString(indent + name)

		// Extract symbols for source files.
		ext := filepath.Ext(name)
		if sourceFileExtensions[ext] {
			data, readErr := os.ReadFile(path)
			if readErr == nil && len(data) <= 256*1024 {
				symbols, symErr := extractSymbols(path, data)
				if symErr == nil && len(symbols) > 0 {
					out.WriteString(" — ")
					out.WriteString(compactSymbolSummary(symbols))
				}
			}
		}

		out.WriteString("\n")
		return nil
	})

	if err != nil && !errors.Is(err, filepath.SkipAll) {
		return "", err
	}

	if truncated {
		out.WriteString(fmt.Sprintf("\n... (%d files shown, more available; use file_list or code_symbols for details)\n", count))
	}

	return FormatResult(out.String()), nil
}

// ────────────────────────────────────────────────────────────────────────────
// Compact symbol summary for inline display in the file tree
// ────────────────────────────────────────────────────────────────────────────

func compactSymbolSummary(symbols []symbolInfo) string {
	var parts []string

	// Group by kind.
	funcs := []string{}
	methods := []string{}
	types := []string{}

	for _, s := range symbols {
		switch s.Kind {
		case "function":
			funcs = append(funcs, s.Name)
		case "method":
			methods = append(methods, s.Name)
		case "class", "interface", "struct", "enum", "trait", "alias", "func", "type", "impl":
			types = append(types, s.Name)
		}
		// Skip imports and package for compact view.
	}

	if len(funcs) > 0 {
		parts = append(parts, fmt.Sprintf("fn: %s", strings.Join(funcs, ", ")))
	}
	if len(methods) > 0 {
		parts = append(parts, fmt.Sprintf("method: %s", strings.Join(methods, ", ")))
	}
	if len(types) > 0 {
		parts = append(parts, fmt.Sprintf("type: %s", strings.Join(types, ", ")))
	}

	return strings.Join(parts, "; ")
}

// ────────────────────────────────────────────────────────────────────────────
// Simple .gitignore matcher
// ────────────────────────────────────────────────────────────────────────────

type gitignoreMatcher struct {
	patterns []string
}

func newGitignoreMatcher(root string) *gitignoreMatcher {
	m := &gitignoreMatcher{}
	// Walk up from root, collecting .gitignore patterns.
	for dir := root; dir != "" && dir != string(filepath.Separator); dir = filepath.Dir(dir) {
		giPath := filepath.Join(dir, ".gitignore")
		data, err := os.ReadFile(giPath)
		if err != nil {
			continue
		}
		for _, line := range strings.Split(string(data), "\n") {
			line = strings.TrimSpace(line)
			if line == "" || strings.HasPrefix(line, "#") {
				continue
			}
			// Remove leading / for anchored patterns; we handle all as relative.
			line = strings.TrimPrefix(line, "/")
			// Remove trailing / for directory-only patterns.
			line = strings.TrimSuffix(line, "/")
			m.patterns = append(m.patterns, line)
		}
	}
	return m
}

func (m *gitignoreMatcher) shouldIgnore(path string, isDir bool) bool {
	name := filepath.Base(path)
	for _, pat := range m.patterns {
		// Simple match against full relative path or just the basename.
		matched, _ := filepath.Match(pat, path)
		if matched {
			return true
		}
		matched, _ = filepath.Match(pat, name)
		if matched {
			return true
		}
	}
	return false
}