package format

import (
	"fmt"
	"strings"
)

// Formatting constants for the 9P chat log protocol.
// Used by fs.NewEventHandler and fs.replayMessagesToLog.
//
// Block format: [[[role:name#blockId]]] or [[[role#blockId]]]
// The blockId is a hex string that uniquely identifies the block.

const (
	// EndTag marks the end of a message block.
	EndTag = "[[[end]]]"

	// RoleTag formats a role delimiter, e.g. "[[[user]]]".
	RoleTag = "[[[%s]]]"

	// ToolFence is the opening fence for tool output blocks.
	ToolFence = "```\n"

	// AssistantHeaderPrefix is prepended to assistant headers when a response ID is present.
	AssistantHeaderPrefix = "[[[assistant:"

	// AssistantTag is the bare assistant header (no response ID).
	AssistantTag = "[[[assistant]]]"

	// UserTag is the user role delimiter.
	UserTag = "[[[user]]]"

	// RetryTag is the retry role delimiter.
	RetryTag = "[[[retry]]]"

	// ToolDelimPrefix is the prefix for tool delimiters, e.g. "[[[tool:shell]]]".
	ToolDelimPrefix = "[[[tool:"

	// ToolTag is the bare tool role delimiter (no name).
	ToolTag = "[[[tool]]]"

	// CallDelimPrefix is the prefix for call delimiters, e.g. "[[[call:file_read]]]".
	CallDelimPrefix = "[[[call:"
)

// RoleDelim returns a formatted role delimiter.
func RoleDelim(role string) string {
	return fmt.Sprintf(RoleTag, role)
}

// ToolDelim returns a formatted tool delimiter.
func ToolDelim(name string) string {
	return fmt.Sprintf(ToolDelimPrefix+"%s]]]\n", name)
}

// CallDelim returns a formatted call delimiter.
func CallDelim(name string) string {
	return fmt.Sprintf(CallDelimPrefix+"%s]]]\n", name)
}

// BlockDelim returns a formatted block delimiter with a block ID.
// Format: [[[role#blockId]]] or [[[role:name#blockId]]]
func BlockDelim(role, name, blockID string) string {
	if name != "" {
		return fmt.Sprintf("[[[%s:%s#%s]]]\n", role, name, blockID)
	}
	return fmt.Sprintf("[[[%s#%s]]]\n", role, blockID)
}

// BlockHeader is a single-line [[[...]]] marker that opens a log block.
type BlockHeader struct {
	Role    string // e.g. "user", "assistant", "tool", "retry", or "tool:shell"
	Name    string // for tool/call: the sub-name (e.g. "shell"), empty for bare roles
	BlockID string // unique block identifier (hex), empty if not present
}

// ParseBlockHeader extracts a BlockHeader from a line like "[[[tool:shell#a1b2]]]"
// or "[[[assistant]]]". Returns nil if the line is not a valid block header.
func ParseBlockHeader(line string) *BlockHeader {
	const prefix, suffix = "[[[", "]]]"
	if !strings.HasPrefix(line, prefix) || !strings.HasSuffix(line, suffix) {
		return nil
	}
	inner := strings.TrimPrefix(line, prefix)
	inner = strings.TrimSuffix(inner, suffix)
	if inner == "" {
		return nil
	}
	bh := &BlockHeader{Role: inner}
	// Extract blockId if present (after #)
	if idx := strings.LastIndex(inner, "#"); idx >= 0 {
		bh.BlockID = inner[idx+1:]
		inner = inner[:idx]
		bh.Role = inner
	}
	// Extract name if present (after :)
	if idx := strings.Index(inner, ":"); idx >= 0 {
		bh.Role = inner[:idx]
		bh.Name = inner[idx+1:]
	}
	return bh
}

// IsEndMarker reports whether the line is exactly the [[[end]]] closing marker.
func IsEndMarker(line string) bool {
	return line == EndTag
}