package hop

import (
	"context"
	"encoding/json"
	"errors"
	"flag"
	"fmt"
	"io"
	"strings"
)

const usageText = `Hop — prompt-native version control

Usage:
  hop init [path]
  hop prompt [--from STATE] [--agent NAME] "instruction"
  hop checkpoint STATE
  hop check STATE -- COMMAND [ARG...]
  hop propose [--summary TEXT] STATE
  hop accept STATE [-- COMMAND [ARG...]]
  hop status
  hop graph
  hop state STATE
  hop env STATE
  hop diff STATE
  hop history
  hop undo
  hop doctor [--repair]
  hop skill install [--path SKILLS_DIR] [--force]
  hop skill print
  hop version

Add --json anywhere for machine-readable output.
`

const Version = "0.1.0-alpha.1"

func RunCLI(args []string, stdout, stderr io.Writer) int {
	jsonOutput, args := removeFlag(args, "--json")
	if len(args) == 0 || args[0] == "help" || args[0] == "--help" || args[0] == "-h" {
		fmt.Fprint(stdout, usageText)
		return 0
	}

	ctx := context.Background()
	command := args[0]
	commandArgs := args[1:]
	if command == "version" || command == "--version" {
		if jsonOutput {
			writeJSON(stdout, map[string]any{"ok": true, "version": Version})
		} else {
			fmt.Fprintf(stdout, "hop %s\n", Version)
		}
		return 0
	}
	if command == "skill" {
		return runSkillCLI(commandArgs, jsonOutput, stdout, stderr)
	}

	if command == "init" {
		path := "."
		if len(commandArgs) > 1 {
			fmt.Fprintln(stderr, "hop init accepts at most one path")
			return 2
		}
		if len(commandArgs) == 1 {
			path = commandArgs[0]
		}
		service, state, err := InitProject(ctx, path)
		if err != nil {
			return printCLIError(err, jsonOutput, stdout, stderr)
		}
		defer service.Close()
		if jsonOutput {
			writeJSON(stdout, map[string]any{"ok": true, "root": service.Root, "state": state})
		} else {
			fmt.Fprintf(stdout, "Initialized Hop at %s\nAccepted %s · tree %s\n", service.Root, state.ID, shortHash(state.SourceTree))
		}
		return 0
	}

	service, err := OpenProject(".")
	if err != nil {
		return printCLIError(err, jsonOutput, stdout, stderr)
	}
	defer service.Close()

	var value any
	switch command {
	case "prompt", "start":
		fs := flag.NewFlagSet("prompt", flag.ContinueOnError)
		fs.SetOutput(stderr)
		from := fs.String("from", "", "continue an existing attempt")
		agent := fs.String("agent", "", "agent or harness name")
		if err := fs.Parse(commandArgs); err != nil {
			return 2
		}
		if len(fs.Args()) != 1 || strings.TrimSpace(fs.Args()[0]) == "" {
			fmt.Fprintln(stderr, "exactly one non-empty prompt argument is required; quote prompts containing spaces")
			return 2
		}
		message := fs.Args()[0]
		result, err := service.CreatePrompt(ctx, message, *from, *agent)
		if err != nil {
			return printCLIError(err, jsonOutput, stdout, stderr)
		}
		value = result
		if !jsonOutput {
			if result.Checkpoint != nil {
				fmt.Fprintf(stdout, "Checkpointed %s before the follow-up\n", result.Checkpoint.ID)
			}
			fmt.Fprintf(stdout, "Created prompt state %s before delivery\nWorkspace: %s\n", result.Prompt.ID, result.Workspace)
			fmt.Fprintf(stdout, "Environment: HOP_ROOT=%s HOP_STATE_ID=%s HOP_TASK_ID=%s HOP_ATTEMPT_ID=%s\n", service.Root, result.Prompt.ID, result.Task.ID, result.Attempt.ID)
		}

	case "checkpoint":
		if len(commandArgs) != 1 {
			fmt.Fprintln(stderr, "usage: hop checkpoint STATE")
			return 2
		}
		state, err := service.Checkpoint(ctx, commandArgs[0])
		if err != nil {
			return printCLIError(err, jsonOutput, stdout, stderr)
		}
		value = state
		if !jsonOutput {
			fmt.Fprintf(stdout, "Created checkpoint %s · tree %s\n", state.ID, shortHash(state.SourceTree))
		}

	case "check":
		stateID, argv, ok := splitCommand(commandArgs)
		if !ok {
			fmt.Fprintln(stderr, "usage: hop check STATE -- COMMAND [ARG...]")
			return 2
		}
		check, err := service.RunCheck(ctx, stateID, argv)
		value = check
		if !jsonOutput {
			fmt.Fprintf(stdout, "$ %s\n%s", shellQuote(check.Command), check.Output)
			if check.Output != "" && !strings.HasSuffix(check.Output, "\n") {
				fmt.Fprintln(stdout)
			}
			fmt.Fprintf(stdout, "Check %s · exit %d · tree %s\n", check.ID, check.ExitCode, shortHash(check.TreeHash))
		}
		if err != nil {
			return printCLIError(err, jsonOutput, stdout, stderr)
		}

	case "propose", "submit":
		fs := flag.NewFlagSet("propose", flag.ContinueOnError)
		fs.SetOutput(stderr)
		summary := fs.String("summary", "", "result summary")
		if err := fs.Parse(commandArgs); err != nil {
			return 2
		}
		if len(fs.Args()) != 1 {
			fmt.Fprintln(stderr, "usage: hop propose [--summary TEXT] STATE")
			return 2
		}
		result, err := service.Propose(ctx, fs.Args()[0], *summary)
		if err != nil {
			return printCLIError(err, jsonOutput, stdout, stderr)
		}
		value = result
		if !jsonOutput {
			fmt.Fprintf(stdout, "Created proposal %s · tree %s · %d matching checks\n", result.Proposal.ID, shortHash(result.Proposal.SourceTree), len(result.Checks))
		}

	case "accept", "land":
		stateID, argv, ok := splitOptionalCommand(commandArgs)
		if !ok {
			fmt.Fprintln(stderr, "usage: hop accept STATE [-- COMMAND [ARG...]]")
			return 2
		}
		result, err := service.Accept(ctx, stateID, argv)
		value = result
		if err != nil {
			return printCLIError(err, jsonOutput, stdout, stderr)
		}
		if !jsonOutput {
			fmt.Fprintf(stdout, "Accepted as %s · tree %s\n", result.State.ID, shortHash(result.State.SourceTree))
			if result.Check == nil {
				fmt.Fprintln(stdout, "No final-state validation command was supplied; acceptance was manual.")
			}
			for _, warning := range result.Warnings {
				fmt.Fprintf(stderr, "Warning: %s\n", warning)
			}
		}

	case "status":
		status, err := service.Status(ctx)
		if err != nil {
			return printCLIError(err, jsonOutput, stdout, stderr)
		}
		value = status
		if !jsonOutput {
			fmt.Fprintf(stdout, "Accepted: %s · tree %s\n", status.AcceptedHead.ID, shortHash(status.AcceptedHead.SourceTree))
			if len(status.Attempts) == 0 {
				fmt.Fprintln(stdout, "No attempts yet.")
			}
			for _, attempt := range status.Attempts {
				fmt.Fprintf(stdout, "%s  %-10s  head=%s  %s\n", attempt.ID, attempt.Status, attempt.HeadStateID, attempt.Workspace)
			}
		}

	case "graph":
		rows, err := service.Graph(ctx)
		if err != nil {
			return printCLIError(err, jsonOutput, stdout, stderr)
		}
		value = rows
		if !jsonOutput {
			for _, row := range rows {
				parents := make([]string, 0, len(row.Parents))
				for _, parent := range row.Parents {
					parents = append(parents, parent.Role+"="+parent.StateID)
				}
				label := row.State.Summary
				if label == "" {
					label = row.State.Prompt
				}
				fmt.Fprintf(stdout, "%-10s %-28s %-50s %s\n", row.State.Kind, row.State.ID, strings.Join(parents, " "), label)
			}
		}

	case "state", "inspect":
		if len(commandArgs) != 1 {
			fmt.Fprintln(stderr, "usage: hop state STATE")
			return 2
		}
		state, err := service.State(ctx, commandArgs[0])
		if err != nil {
			return printCLIError(err, jsonOutput, stdout, stderr)
		}
		value = state
		if !jsonOutput {
			fmt.Fprintf(stdout, "%s %s\nTree: %s\nCommit: %s\nDigest: %s\n", state.Kind, state.ID, state.SourceTree, state.GitCommit, state.Digest)
			if state.Prompt != "" {
				fmt.Fprintf(stdout, "Prompt: %s\n", state.Prompt)
			}
			if state.Summary != "" {
				fmt.Fprintf(stdout, "Summary: %s\n", state.Summary)
			}
			for _, parent := range state.Parents {
				fmt.Fprintf(stdout, "Parent: %-18s %s\n", parent.Role, parent.StateID)
			}
		}

	case "env":
		if len(commandArgs) != 1 {
			fmt.Fprintln(stderr, "usage: hop env STATE")
			return 2
		}
		result, err := service.EnvironmentForState(ctx, commandArgs[0])
		if err != nil {
			return printCLIError(err, jsonOutput, stdout, stderr)
		}
		value = result
		if !jsonOutput {
			for _, name := range []string{"HOP_ROOT", "HOP_STATE_ID", "HOP_TASK_ID", "HOP_ATTEMPT_ID", "HOP_WORKSPACE"} {
				fmt.Fprintf(stdout, "export %s=%s\n", name, shellQuote([]string{result.Variables[name]}))
			}
			fmt.Fprintf(stdout, "cd %s\n", shellQuote([]string{result.Workspace}))
		}

	case "diff":
		if len(commandArgs) != 1 {
			fmt.Fprintln(stderr, "usage: hop diff STATE")
			return 2
		}
		diff, err := service.Diff(ctx, commandArgs[0])
		if err != nil {
			return printCLIError(err, jsonOutput, stdout, stderr)
		}
		value = map[string]string{"state": commandArgs[0], "diff": diff}
		if !jsonOutput {
			fmt.Fprint(stdout, diff)
		}

	case "history":
		states, err := service.History(ctx)
		if err != nil {
			return printCLIError(err, jsonOutput, stdout, stderr)
		}
		value = states
		if !jsonOutput {
			for _, state := range states {
				fmt.Fprintf(stdout, "%s  %s  %s\n", state.ID, shortHash(state.SourceTree), state.Summary)
			}
		}

	case "undo":
		if len(commandArgs) != 0 {
			fmt.Fprintln(stderr, "usage: hop undo")
			return 2
		}
		state, err := service.Undo(ctx)
		var committed *CommittedStateError
		if err != nil && !errors.As(err, &committed) {
			return printCLIError(err, jsonOutput, stdout, stderr)
		}
		if committed != nil {
			state = committed.State
			value = map[string]any{"state": state, "warnings": []string{committed.Error()}}
		} else {
			value = state
		}
		if !jsonOutput {
			fmt.Fprintf(stdout, "Created forward undo state %s · tree %s\n", state.ID, shortHash(state.SourceTree))
			if committed != nil {
				fmt.Fprintf(stderr, "Warning: %s\n", committed.Error())
			}
		}

	case "doctor":
		fs := flag.NewFlagSet("doctor", flag.ContinueOnError)
		fs.SetOutput(stderr)
		repair := fs.Bool("repair", false, "repair the internal accepted ref")
		if err := fs.Parse(commandArgs); err != nil || len(fs.Args()) != 0 {
			return 2
		}
		report, err := service.Doctor(ctx, *repair)
		if err != nil {
			return printCLIError(err, jsonOutput, stdout, stderr)
		}
		value = report
		if !jsonOutput {
			if report.OK {
				fmt.Fprintf(stdout, "Hop project is healthy · %s\n", report.AcceptedState)
			} else {
				for _, problem := range report.Problems {
					fmt.Fprintf(stdout, "Problem: %s\n", problem)
				}
			}
		}

	default:
		fmt.Fprintf(stderr, "unknown command %q\n\n%s", command, usageText)
		return 2
	}

	if jsonOutput {
		writeJSON(stdout, map[string]any{"ok": true, "data": value})
	}
	return 0
}

func runSkillCLI(args []string, jsonOutput bool, stdout, stderr io.Writer) int {
	if len(args) == 0 {
		fmt.Fprintln(stderr, "usage: hop skill install [--path SKILLS_DIR] [--force] | hop skill print")
		return 2
	}
	switch args[0] {
	case "install":
		fs := flag.NewFlagSet("skill install", flag.ContinueOnError)
		fs.SetOutput(stderr)
		path := fs.String("path", "", "parent skills directory")
		force := fs.Bool("force", false, "update an existing Hop skill")
		if err := fs.Parse(args[1:]); err != nil || len(fs.Args()) != 0 {
			return 2
		}
		result, err := InstallSkill(*path, *force)
		if err != nil {
			return printCLIError(err, jsonOutput, stdout, stderr)
		}
		if jsonOutput {
			writeJSON(stdout, map[string]any{"ok": true, "data": result})
		} else {
			fmt.Fprintf(stdout, "Installed Hop skill at %s\n", result.Path)
		}
		return 0
	case "print":
		if len(args) != 1 {
			fmt.Fprintln(stderr, "usage: hop skill print")
			return 2
		}
		contents, err := EmbeddedSkillText()
		if err != nil {
			return printCLIError(err, jsonOutput, stdout, stderr)
		}
		if jsonOutput {
			writeJSON(stdout, map[string]any{"ok": true, "data": map[string]string{"skill": contents}})
		} else {
			fmt.Fprint(stdout, contents)
		}
		return 0
	default:
		fmt.Fprintf(stderr, "unknown skill command %q\n", args[0])
		return 2
	}
}

func printCLIError(err error, jsonOutput bool, stdout, stderr io.Writer) int {
	code := 1
	var conflict *ConflictError
	var stale *StaleHeadError
	var failed *CheckFailedError
	switch {
	case errors.As(err, &conflict):
		code = 20
	case errors.As(err, &stale):
		code = 21
	case errors.As(err, &failed):
		code = 22
	}
	if jsonOutput {
		writeJSON(stdout, map[string]any{"ok": false, "error": err.Error(), "exit_code": code})
	} else {
		fmt.Fprintf(stderr, "hop: %v\n", err)
		if conflict != nil && len(conflict.Paths) > 0 {
			fmt.Fprintln(stderr, "Overlapping paths:")
			for _, path := range conflict.Paths {
				fmt.Fprintf(stderr, "  %s\n", path)
			}
		}
	}
	return code
}

func removeFlag(args []string, wanted string) (bool, []string) {
	found := false
	filtered := make([]string, 0, len(args))
	for i, arg := range args {
		if arg == "--" {
			filtered = append(filtered, args[i:]...)
			break
		}
		if arg == wanted {
			found = true
			continue
		}
		filtered = append(filtered, arg)
	}
	return found, filtered
}

func splitCommand(args []string) (string, []string, bool) {
	if len(args) < 3 || args[1] != "--" {
		return "", nil, false
	}
	return args[0], args[2:], len(args[2:]) > 0
}

func splitOptionalCommand(args []string) (string, []string, bool) {
	if len(args) == 1 {
		return args[0], nil, true
	}
	if len(args) >= 3 && args[1] == "--" {
		return args[0], args[2:], true
	}
	return "", nil, false
}

func writeJSON(w io.Writer, value any) {
	encoder := json.NewEncoder(w)
	encoder.SetIndent("", "  ")
	_ = encoder.Encode(value)
}

func shortHash(hash string) string {
	if len(hash) <= 12 {
		return hash
	}
	return hash[:12]
}