package main

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"net/http"
	"os/exec"
	"path/filepath"
	"strings"
	"time"

	"fn-registry/functions/infra"
)

const chatSystemPrompt = `Eres el asistente del tablero kanban. Tu trabajo es responder al usuario y, cuando pida cambios, modificar el tablero llamando a tools.

Cuando necesites modificar el tablero, responde EXCLUSIVAMENTE con un bloque <actions>...</actions> que contenga JSON valido (un array de acciones). Sin texto antes ni despues.

Ejemplo:
<actions>
[
  {"tool": "create_card", "input": {"column_id": "abc123", "requester": "Lucas", "title": "Revisar PR", "description": ""}},
  {"tool": "rename_column", "input": {"id": "def456", "name": "En curso"}}
]
</actions>

Tools disponibles (todas con sus inputs):
- list_board {} -> {columns, cards}
- create_column {name}
- update_column {id, name?, location?, width?, wip_limit?, is_done?}  // location: "board" | "sidebar". width: 200..800 px. wip_limit: max tarjetas (0 = sin limite). is_done: marca columna como terminal (cards dentro se cuentan como completadas para metricas y se muestran tachadas).
- delete_column {id}
- reorder_columns {ids:[...]}
- create_card {column_id, requester?, title, description?}
- update_card {id, requester?, title?, description?, color?, locked?, assignee_id?}  // color: "blue", "teal", "violet", "pink", "orange", "green", "yellow", "red", "" (default). locked: true bloquea la tarjeta (no se puede mover entre columnas hasta desbloquear). assignee_id: ID del usuario asignado o null para desasignar.
- delete_card {id}
- move_card {id, column_id, ordered_ids?}  // si omites ordered_ids la tarjeta se anade al final
- card_history {id}
- find_cards {query?, column_id?, requester?}
- list_users {} -> [{id, username, display_name}]
- assign_card {id, assignee_id}  // alias rapido de update_card. assignee_id puede ser null para desasignar.

Si el usuario solo conversa o pide informacion (sin pedir cambios), responde texto natural en markdown SIN bloque <actions>.

Para resolver IDs a partir de nombres, mira el board_state que viene al final del prompt del usuario. NO inventes IDs.

LOOP ITERATIVO: Despues de aplicar tus acciones, el sistema te volvera a llamar con:
- Los resultados de las tool calls anteriores (incluyendo IDs reales de columnas/tarjetas creadas).
- El board_state actualizado.
- Tu mensaje de usuario original.

Cuando recibas resultados de iteraciones anteriores, USA LOS IDs REALES devueltos en lugar de inventar placeholders. Continua emitiendo mas <actions> hasta completar la tarea.

Cuando hayas terminado COMPLETAMENTE la tarea, responde texto natural (markdown) SIN bloque <actions> — eso señala el fin del loop.`

const claudeBin = "claude"
const claudeModel = "claude-sonnet-4-6"
const claudeTimeout = 120 * time.Second
const maxChatIterations = 8

type chatMessage struct {
	Role    string `json:"role"`
	Content string `json:"content"`
}

type chatRequest struct {
	Messages []chatMessage `json:"messages"`
}

type chatResponse struct {
	Role         string         `json:"role"`
	Content      string         `json:"content"`
	BoardChanged bool           `json:"board_changed"`
	ToolCalls    []toolCallInfo `json:"tool_calls,omitempty"`
}

type toolCallInfo struct {
	Tool      string `json:"tool"`
	OK        bool   `json:"ok"`
	Error     string `json:"error,omitempty"`
	Iteration int    `json:"iteration,omitempty"`
	// Result is included only for the loop's internal feedback to claude;
	// it is omitted from the JSON response sent to the frontend (clients
	// can use board_changed + reload to fetch fresh state).
	Result any `json:"-"`
}

type claudeJSONResult struct {
	Type      string `json:"type"`
	IsError   bool   `json:"is_error"`
	Result    string `json:"result"`
	StopReason string `json:"stop_reason"`
}

// runClaude invokes the `claude` CLI in print mode with the given system prompt
// and user message. The board JSON is appended to the user message under a
// `board_state` marker so the assistant can resolve names to IDs.
//
// stdin: the user-facing prompt (history flattened).
// returns: assistant's text reply.
func runClaude(ctx context.Context, systemPrompt, userInput, boardJSON, workdir string) (string, error) {
	if _, err := exec.LookPath(claudeBin); err != nil {
		return "", errors.New("claude CLI not found in PATH")
	}

	ctx, cancel := context.WithTimeout(ctx, claudeTimeout)
	defer cancel()

	cmd := exec.CommandContext(ctx, claudeBin,
		"-p",
		"--model", claudeModel,
		"--output-format", "json",
		"--no-session-persistence",
		"--tools", "",
		"--system-prompt", systemPrompt,
	)
	cmd.Dir = workdir

	prompt := userInput
	if boardJSON != "" {
		prompt += "\n\n<board_state>\n" + boardJSON + "\n</board_state>\n"
	}
	cmd.Stdin = bytes.NewBufferString(prompt)

	var stdout, stderr bytes.Buffer
	cmd.Stdout = &stdout
	cmd.Stderr = &stderr

	if err := cmd.Run(); err != nil {
		return "", fmt.Errorf("claude exec: %w (stderr: %s)", err, stderr.String())
	}

	var res claudeJSONResult
	if err := json.Unmarshal(stdout.Bytes(), &res); err != nil {
		return "", fmt.Errorf("parse claude json: %w (raw: %s)", err, stdout.String())
	}
	if res.IsError {
		return "", fmt.Errorf("claude error: %s", res.Result)
	}
	return res.Result, nil
}

// flattenMessages converts a chat history into a single text prompt for `claude -p`.
// Format: lines of `Usuario: ...` / `Asistente: ...`. Last user message ends the prompt.
func flattenMessages(msgs []chatMessage) string {
	var b bytes.Buffer
	for _, m := range msgs {
		role := "Usuario"
		if m.Role == "assistant" {
			role = "Asistente"
		}
		b.WriteString(role)
		b.WriteString(": ")
		b.WriteString(m.Content)
		b.WriteString("\n\n")
	}
	return b.String()
}

func handleChat(db *DB, workdir string, logger *ChatLogger) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		var req chatRequest
		if err := infra.HTTPParseBody(r, &req, 1<<20); err != nil {
			infra.HTTPErrorResponse(w, infra.HTTPError{Status: 400, Code: "bad_request", Message: err.Error()})
			return
		}
		if len(req.Messages) == 0 {
			infra.HTTPErrorResponse(w, infra.HTTPError{Status: 400, Code: "bad_request", Message: "messages required"})
			return
		}

		baseUserInput := flattenMessages(req.Messages)
		allCalls := []toolCallInfo{}
		var finalText string
		boardChanged := false

		for iter := 1; iter <= maxChatIterations; iter++ {
			boardJSON, err := boardSnapshot(db)
			if err != nil {
				infra.HTTPErrorResponse(w, infra.HTTPError{Status: 500, Code: "internal", Message: err.Error()})
				return
			}

			prompt := buildIterationPrompt(baseUserInput, allCalls, iter)

			assistantText, err := runClaude(r.Context(), chatSystemPrompt, prompt, boardJSON, workdir)
			if err != nil {
				infra.HTTPErrorResponse(w, infra.HTTPError{Status: 500, Code: "claude_error", Message: err.Error()})
				return
			}

			actionsJSON, stripped, found := extractActions(assistantText)
			if !found {
				finalText = assistantText
				break
			}

			calls, changed := applyActions(db, actionsJSON, logger)
			for i := range calls {
				calls[i].Iteration = iter
			}
			allCalls = append(allCalls, calls...)
			if changed {
				boardChanged = true
			}

			finalText = stripped // tentative; overwritten if next iter responds free text
			if iter == maxChatIterations {
				finalText = strings.TrimSpace(stripped + "\n\n_Limite de iteraciones alcanzado._")
				break
			}
		}

		// Strip Result fields before serializing (not exported but defensive).
		respCalls := make([]toolCallInfo, len(allCalls))
		for i, c := range allCalls {
			respCalls[i] = toolCallInfo{Tool: c.Tool, OK: c.OK, Error: c.Error, Iteration: c.Iteration}
		}
		resp := chatResponse{
			Role:         "assistant",
			Content:      finalText,
			ToolCalls:    respCalls,
			BoardChanged: boardChanged,
		}
		if resp.Content == "" {
			resp.Content = summarizeCalls(respCalls)
		}
		infra.HTTPJSONResponse(w, http.StatusOK, resp)
	}
}

// buildIterationPrompt composes the user prompt for iteration N.
// Iteration 1 = original user input; later iterations also include a summary
// of previous tool calls so the assistant can use real IDs.
func buildIterationPrompt(baseUserInput string, prevCalls []toolCallInfo, iter int) string {
	if iter == 1 || len(prevCalls) == 0 {
		return baseUserInput
	}
	var b bytes.Buffer
	b.WriteString(baseUserInput)
	b.WriteString("\n[Resultados de iteraciones anteriores]\n")
	for _, c := range prevCalls {
		if c.OK {
			summary := summarizeResult(c.Result)
			fmt.Fprintf(&b, "- iter %d %s: ok %s\n", c.Iteration, c.Tool, summary)
		} else {
			fmt.Fprintf(&b, "- iter %d %s: ERROR %s\n", c.Iteration, c.Tool, c.Error)
		}
	}
	fmt.Fprintf(&b, "\n[Iteracion %d] Continua con las acciones pendientes. Si terminaste, responde texto natural sin <actions>.\n", iter)
	return b.String()
}

func boardSnapshot(db *DB) (string, error) {
	cols, err := db.ListColumns()
	if err != nil {
		return "", err
	}
	cards, err := db.ListCardsWithTime()
	if err != nil {
		return "", err
	}
	b, err := json.MarshalIndent(map[string]any{"columns": cols, "cards": cards}, "", "  ")
	if err != nil {
		return "", err
	}
	return string(b), nil
}

func applyActions(db *DB, actionsJSON string, logger *ChatLogger) ([]toolCallInfo, bool) {
	var actions []struct {
		Tool  string          `json:"tool"`
		Input json.RawMessage `json:"input"`
	}
	if err := json.Unmarshal([]byte(actionsJSON), &actions); err != nil {
		return []toolCallInfo{{Tool: "<parse>", OK: false, Error: err.Error()}}, false
	}

	results := make([]toolCallInfo, 0, len(actions))
	changed := false
	for _, a := range actions {
		if err := validateToolName(a.Tool); err != nil {
			info := toolCallInfo{Tool: a.Tool, OK: false, Error: err.Error()}
			results = append(results, info)
			logger.Log(a.Tool, a.Input, ToolResult{OK: false, Error: err.Error()})
			continue
		}
		res := executeTool(db, a.Tool, a.Input)
		logger.Log(a.Tool, a.Input, res)
		info := toolCallInfo{Tool: a.Tool, OK: res.OK, Result: res.Result}
		if !res.OK {
			info.Error = res.Error
		} else if toolMutates(a.Tool) {
			changed = true
		}
		results = append(results, info)
	}
	return results, changed
}

func summarizeCalls(calls []toolCallInfo) string {
	if len(calls) == 0 {
		return ""
	}
	var b bytes.Buffer
	b.WriteString("Acciones aplicadas:\n")
	for _, c := range calls {
		if c.OK {
			fmt.Fprintf(&b, "- %s: ok\n", c.Tool)
		} else {
			fmt.Fprintf(&b, "- %s: error (%s)\n", c.Tool, c.Error)
		}
	}
	return b.String()
}

// chatWorkdir resolves an absolute working directory for `claude -p` (avoids
// inheriting CLAUDE.md from parent directories with unrelated context).
func chatWorkdir(dbPath string) string {
	abs, err := filepath.Abs(dbPath)
	if err != nil {
		return "."
	}
	return filepath.Dir(abs)
}