package tools

import (
	"context"
	"encoding/json"
	"fmt"
	"sort"
	"strings"

	"agentu/pkg/llm"
)

const MaxToolOutputBytes = 64 * 1024

const truncationNoticeBudget = 160

type Tool interface {
	Definition() llm.Tool
	Execute(ctx context.Context, args json.RawMessage) (string, error)
}

// MutatingTool is optionally implemented by tools that modify external state.
// It is used by the agent to determine whether tool calls can run in parallel.
type MutatingTool interface {
	Mutates() bool
}

// IsMutating reports whether tool implements MutatingTool and returns true.
func IsMutating(tool Tool) bool {
	mutating, ok := tool.(MutatingTool)
	return ok && mutating.Mutates()
}

type Registry struct {
	tools   map[string]Tool
	primary []string
}

func NewRegistry(items ...Tool) *Registry {
	r := &Registry{tools: make(map[string]Tool, len(items))}
	for _, item := range items {
		r.Register(item)
	}
	return r
}

func (r *Registry) Register(tool Tool) {
	name := tool.Definition().Function.Name
	if _, exists := r.tools[name]; !exists {
		r.primary = append(r.primary, name)
	}
	r.tools[name] = tool
}

func (r *Registry) RegisterAlias(alias string, tool Tool) {
	r.tools[alias] = tool
}

func (r *Registry) Get(name string) (Tool, bool) {
	tool, ok := r.tools[name]
	return tool, ok
}

func (r *Registry) Definitions() []llm.Tool {
	defs := make([]llm.Tool, 0, len(r.primary))
	for _, name := range r.primary {
		tool := r.tools[name]
		defs = append(defs, tool.Definition())
	}
	sort.Slice(defs, func(i, j int) bool {
		return defs[i].Function.Name < defs[j].Function.Name
	})
	return defs
}

func ReadOnlyBuiltins(workingDir string) *Registry {
	fileRead := NewFileReadTool(workingDir)
	fileList := NewFileListTool(workingDir)
	fileSearch := NewFileSearchTool(workingDir)
	codeSymbols := NewCodeSymbolsTool(workingDir)
	gitStatus := NewGitStatusTool(workingDir)
	gitDiff := NewGitDiffTool(workingDir)
	gitLog := NewGitLogTool(workingDir)

	registry := NewRegistry(fileRead, fileList, fileSearch, codeSymbols, gitStatus, gitDiff, gitLog)
	registry.RegisterAlias("file.read", fileRead)
	registry.RegisterAlias("file.list", fileList)
	registry.RegisterAlias("file.search", fileSearch)
	registry.RegisterAlias("code.symbols", codeSymbols)
	registry.RegisterAlias("git.status", gitStatus)
	registry.RegisterAlias("git.diff", gitDiff)
	registry.RegisterAlias("git.log", gitLog)
	return registry
}

func Builtins(workingDir string) *Registry {
	registry := ReadOnlyBuiltins(workingDir)
	fileWrite := NewFileWriteTool(workingDir)
	fileEdit := NewFileEditTool(workingDir)
	shellRun := NewShellRunTool(workingDir)
	registry.Register(fileWrite)
	registry.Register(fileEdit)
	registry.Register(shellRun)
	registry.RegisterAlias("file.write", fileWrite)
	registry.RegisterAlias("file.edit", fileEdit)
	registry.RegisterAlias("shell.run", shellRun)
	return registry
}

func AgentInstructions(workingDir string, yolo bool) string {
	searchInstructions := webSearchInstructions()
	readOnlyTools := "file_list, file_read, file_search, code_symbols, git_status, git_diff, git_log, web_search, web_fetch"
	yoloTools := "file_list, file_read, file_search, code_symbols, file_write, file_edit, shell_run, git_status, git_diff, git_log, web_search, web_fetch"
	if yolo {
		return fmt.Sprintf(`Local project context:
- The project working directory is %q.
- Tools are available, but use them only when needed to satisfy the user's request.
- Do not call tools for greetings, small talk, simple Q&A, or general questions that do not require local project or command context.
- Do not explore the project preemptively. Do not call file_list just to discover context unless the user asks about project files or the answer truly depends on local files.
- When the user asks to inspect, list, search, or read project files, use file_list, file_search, and file_read instead of saying you cannot access local files.
- When the user asks about code structure, symbols, functions, methods, types, or definitions in Go files, use code_symbols before reading whole files.
- When the user asks to run, execute, test, check, debug, or inspect a shell command, use shell_run. This includes local commands written in backticks, such as go, make, git, pwd, ls, ps, and similar terminal commands.
- When editing existing files, prefer file_edit for small or localized changes; use file_write only for creating files, replacing whole files intentionally, or appending.
- Do not use file tools as a substitute for a command execution request.
- When the user asks about changed files, diffs, or git history, use git_status, git_diff, or git_log instead of shell_run.
- Do not start interactive or long-running sessions. Prefer bounded, non-interactive local commands with clear completion conditions.
- %s
- Tool paths should normally be relative to the project working directory.
- Available tools: %s.`, workingDir, searchInstructions, yoloTools)
	}
	return fmt.Sprintf(`Local project context:
- The project working directory is %q.
- Read-only project file tools are available, but use them only when needed to satisfy the user's request.
- Do not call tools for greetings, small talk, simple Q&A, or general questions that do not require local project context.
- Do not explore the project preemptively. Do not call file_list just to discover context unless the user asks about project files or the answer truly depends on local files.
- When the user asks to inspect, list, search, or read project files, use file_list, file_search, and file_read instead of saying you cannot access local files.
- When the user asks about code structure, symbols, functions, methods, types, or definitions in Go files, use code_symbols before reading whole files.
- Shell command execution is disabled in this mode. When the user asks to run, execute, test, check, debug, or inspect a shell command, do not use file tools as a substitute; explain that they need to restart agentu with --yolo to enable shell_run.
- When the user asks about changed files, diffs, or git history, use git_status, git_diff, or git_log instead of shell_run.
- %s
- Tool paths should normally be relative to the project working directory.
- Available tools: %s.`, workingDir, searchInstructions, readOnlyTools)
}

func webSearchInstructions() string {
	return "When the user's request depends on current or external web information, use web_search. This includes news, prices, laws, schedules, software versions, product recommendations, or requests for the latest information. Use web_fetch to read a source URL when search snippets are not enough, when the user provides a URL, or when the user names a specific website to inspect. Base answers on returned sources and include source URLs when useful."
}

func JSONSchema(schema string) json.RawMessage {
	return json.RawMessage(schema)
}

func FormatResult(output string) string {
	return FormatResultLimit(output, MaxToolOutputBytes)
}

func FormatResultLimit(output string, limit int) string {
	if limit <= 0 || len(output) <= limit {
		return output
	}
	if limit <= truncationNoticeBudget {
		return output[:limit]
	}
	notice := fmt.Sprintf("\n\n[truncated: showing head and tail; omitted %d bytes]\n\n", len(output)-limit)
	keep := limit - len(notice)
	if keep <= 0 {
		return output[:limit]
	}
	headLen := keep / 2
	tailLen := keep - headLen
	head := trimHeadAtLine(output[:headLen])
	tail := trimTailAtLine(output[len(output)-tailLen:])
	return head + notice + tail
}

func trimHeadAtLine(value string) string {
	if idx := strings.LastIndexByte(value, '\n'); idx > 0 {
		return value[:idx+1]
	}
	return value
}

func trimTailAtLine(value string) string {
	if idx := strings.IndexByte(value, '\n'); idx >= 0 && idx+1 < len(value) {
		return value[idx+1:]
	}
	return value
}

func FormatError(err error) string {
	return "error: " + err.Error()
}