import {
	App,
	Editor,
	EditorPosition,
	MarkdownView,
	Plugin,
	PluginSettingTab,
	Setting,
} from "obsidian";

import { EditorView } from "@codemirror/view";

import { Symbol } from "src/symbol";
import { LHS, RHS, Snippet, SnippetType } from "src/snippet";

enum AutoTriggerOptions {
	Disabled = "disabled",
	EnabledNoWS = "n-ws",
	EnabledYesWS = "y-ws",
}

interface JellySnippetsSettings {
	snippetsFile: string;
	triggerOnSpace: AutoTriggerOptions;
	triggerOnEnter: AutoTriggerOptions;
	triggerOnTab: AutoTriggerOptions;
	snippetPartDivider: string;
	snippetDivider: string;
}

const DEFAULT_SETTINGS: JellySnippetsSettings = {
	snippetsFile: String.raw`Snip me! |+| Snippet successfully replaced.
-==-
- |+| #####
-==-
: |+| -
-==-
:: |+| hi`,
	triggerOnSpace: AutoTriggerOptions.Disabled,
	triggerOnEnter: AutoTriggerOptions.Disabled,
	triggerOnTab: AutoTriggerOptions.Disabled,
	snippetPartDivider: " |+| ",
	snippetDivider: "-==-",
};

export default class JellySnippets extends Plugin {
	settings: JellySnippetsSettings;
	private multilineSnippets: { [key: LHS]: RHS } = {};

	async onload() {
		await this.loadSettings();

		// Check settings and load snippets in.
		this.reloadSnippets();

		// If keydown events are set...
		if (
			this.settings.triggerOnSpace !== AutoTriggerOptions.Disabled ||
			this.settings.triggerOnTab !== AutoTriggerOptions.Disabled ||
			this.settings.triggerOnEnter !== AutoTriggerOptions.Disabled
		) {
			const onKeyEvent = (evt: KeyboardEvent) => {
				if (
					!evt.shiftKey // TODO: add function to determine when not to trigger. don't trigger if shift is pressed down as well e.g.
				) {
					const mdFile = this.app.workspace.activeEditor;
					if (mdFile?.editor) {
						this.triggerSnippetAutomatically(mdFile.editor, evt);
					}
				}
			};

			// Register for main window.
			this.registerDomEvent(document, "keydown", onKeyEvent);

			// If window changes, registerDomEvent for new window if so.
			this.registerEvent(
				this.app.workspace.on("window-open", (event) => {
					this.registerDomEvent(activeWindow, "keydown", onKeyEvent);
				})
			);
		}

		this.addCommand({
			id: "trigger-snippet",
			name: "Trigger snippet",
			editorCallback: (editor: Editor) => {
				this.triggerSnippet(editor);
			},
		});

		this.addCommand({
			id: "reload-snippets",
			name: "Reload snippets",
			callback: () => {
				this.reloadSnippets();
			},
		});

		this.addSettingTab(new JellySnippetsSettingTab(this.app, this));
	}

	onunload() {}

	async loadSettings() {
		this.settings = Object.assign(
			{},
			DEFAULT_SETTINGS,
			await this.loadData()
		);
	}

	async saveSettings() {
		await this.saveData(this.settings);
	}

	reloadSnippets(): void {
		console.log("Jelly Snippets: Reloading snippets.");
		this.multilineSnippets = {};
		this.parseSnippets();
	}

	parseSnippets(): void {
		// If they specified newline control character, split snippets by newline.
		// TODO: Can we make it so that leaving the setting blank is newline separation?
		let snippetDivider =
			this.settings.snippetDivider == "\\n"
				? "\n"
				: this.settings.snippetDivider + "\n";

		// go through the snippets file, split by the snippet divider, split by the part divider, put in map
		let snippetLines = this.settings.snippetsFile.split(snippetDivider);
		for (let snippet of snippetLines) {
			// Trim newlines. Instead, use symbols to let people insert whitespace.
			// This split means only the first division of the part divider is the LHS.
			let snippetParts = snippet
				.trimEnd()
				.split(this.settings.snippetPartDivider);
			if (snippetParts.length !== 2) {
				// probably an incomplete snippet
				continue;
			}
			// Produce lhs. Continue if undefined.
			let lhs = snippetParts.shift();
			if (lhs === undefined) {
				console.log("Failed to register snippet: ", snippet);
				continue;
			}
			// Produce rhs (raw data).
			// * This is a join in case they used their snippetPartDivider too many times.
			let rhsData = snippetParts.join(this.settings.snippetPartDivider);
			// Scan rhs for symbols and perform the replacements; acquire RHS.
			let rhs = Symbol.replaceSymbolsOnParse(rhsData);
			this.multilineSnippets[lhs] = rhs;
		}
	}

	triggerSnippet(editor: Editor, pos?: EditorPosition): Snippet | undefined {
		let curpos = pos ? pos : editor.getCursor();
		return this.triggerMultilineSnippet(editor, curpos);
	}

	triggerSnippetAutomatically(editor: Editor, evt: KeyboardEvent) {
		// remember the order: enter and tab come out before code triggers, space comes out after.
		switch (evt.key) {
			case " ": {
				if (
					this.settings.triggerOnSpace !== AutoTriggerOptions.Disabled
				) {
					if (this.triggerSnippet(editor)) {
						// Currently impossible to undo the space because the entire snippet
						// and all this code triggers before the space actually happens.
						return true;
					}
				}
				break;
			}
			case "Tab": {
				if (
					this.settings.triggerOnTab === AutoTriggerOptions.Disabled
				) {
					return false;
				}
				editor.exec("indentLess");
				let maybeSnippet = this.triggerSnippet(editor);
				if (maybeSnippet) {
					if (
						this.settings.triggerOnTab ===
						AutoTriggerOptions.EnabledYesWS
					) {
						if (
							this.getSnippetType(maybeSnippet) ===
							SnippetType.SLSR
						) {
							editor.exec("indentMore");
						}
					}
					return true;
				} else {
					// If no snippet was triggered, restore the user's indent!
					editor.exec("indentMore");
				}
				break;
			}
			case "Enter": {
				if (
					this.settings.triggerOnEnter === AutoTriggerOptions.Disabled
				) {
					return false;
				}
				// Since the newline comes out first, we need to find our old position before newline (peekPos).
				let curpos = editor.getCursor();
				let aboveline = curpos.line - 1;
				let abovelineEnd = editor.getLine(aboveline).length;
				let peekPos: EditorPosition = {
					line: aboveline,
					ch: abovelineEnd,
				};
				// Try to trigger the snippet at the old position.
				let maybeSnippet = this.triggerSnippet(editor, peekPos);

				// If the snippet triggered, clean up the newline.
				if (maybeSnippet) {
					// delete newline at the end of snippet
					let curpos = editor.getCursor();
					let curoffset = editor.posToOffset(curpos);
					// get end of replacement part
					let rhsEndOffset =
						curoffset + maybeSnippet.rhs.info.cursorEnd;
					let rhsEndPos = editor.offsetToPos(rhsEndOffset);
					// the line after that (works at document end)
					let afterSnippetLinePos = {
						line: rhsEndPos.line + 1,
						ch: 0,
					};
					editor.replaceRange("", rhsEndPos, afterSnippetLinePos);

					// If they want the newline added where the cursor is at (works weird for cursorEnd snippets but eh)
					// TODO: maybe make another setting where add newline on enter is disabled if snippet has a cursorEnd?
					if (
						this.settings.triggerOnEnter ===
						AutoTriggerOptions.EnabledYesWS
					) {
						// Insert newline where we are at.
						editor.exec("newlineAndIndent");
						curpos = editor.getCursor();
						// To "de-indent", delete until start of line.
						editor.replaceRange(
							"",
							{
								line: curpos.line,
								ch: 0,
							},
							curpos
						);
					}

					return true;
				} else {
					// Didn't trigger; move the cursor back down
					editor.setCursor(curpos);
				}
				break;
			}
			default: {
				break;
			}
		}
		return false;
	}

	triggerMultilineSnippet(
		editor: Editor,
		pos?: EditorPosition
	): Snippet | undefined {
		const curpos = pos ? pos : editor.getCursor();
		const curoffset = editor.posToOffset(curpos);

		// @ts-expect-error
		const view = editor.cm as EditorView;

		for (let [lhs, rhs] of Object.entries(this.multilineSnippets)) {
			const from = curoffset - lhs.length;
			const to = curoffset;

			// Get the text just before the cursor
			let selected = view.state.sliceDoc(from, to);

			if (lhs === selected) {
				// Dispatch the replacement and move the cursor to where it should be.
				view.dispatch({
					changes: [
						{
							from,
							to,
							insert: rhs.data,
						},
					],
					selection: {
						anchor: from + rhs.data.length - rhs.info.cursorEnd,
					},
				});

				// Return what you replaced.
				return { lhs, rhs };
			}
		}

		// No replace - return undefined
		return;
	}

	// Motivation:
	// Single snippets (no newlines) and multi snippets (newlines)
	// have different, weird interaction with Obsidian. Sometimes the whitespace goes through, sometimes not.
	// There needs to be a way of determining what type (mlhs->srhs? mlhs->mrhs? slhs? srhs? etc.) a snippet is.
	getSnippetType(snippet: Snippet): SnippetType {
		let { lhs, rhs } = snippet;
		let type = SnippetType.SLSR;
		// Compiler doesn't complain if we convert boolean to number with unary '+'.
		type |= +lhs.includes("\n") ? SnippetType.MLSR : 0;
		type |= +rhs.info.hasNewline ? SnippetType.SLMR : 0;
		return type;
	}

	selectBackN(editor: Editor, N: number, pos?: EditorPosition): boolean {
		const curpos = pos ? pos : editor.getCursor();

		// pos -> offset; offset - N; offsetToPos; select offsets
		let endOffset = editor.posToOffset(curpos);
		let startOffset = endOffset - N;

		// If we can't select back N because we are too close to the start:
		if (startOffset < 0) {
			return false;
		}

		// * In selection terms, anchor is where you first click and head is where you drag to.
		// Try to keep head at the end position and anchor at the start.
		let startPos = editor.offsetToPos(startOffset);
		let endPos = editor.offsetToPos(endOffset);
		editor.setSelection(startPos, endPos);
		return true;
	}

	unselect(editor: Editor, pos?: EditorPosition) {
		if (pos) editor.setSelection(pos, pos);
		else editor.setSelection(editor.getCursor(), editor.getCursor());
	}
}

class JellySnippetsSettingTab extends PluginSettingTab {
	plugin: JellySnippets;

	constructor(app: App, plugin: JellySnippets) {
		super(app, plugin);
		this.plugin = plugin;
	}

	display(): void {
		const { containerEl } = this;

		containerEl.empty();

		let childEl = containerEl.createDiv({ cls: "jelly_snippets" });

		childEl.createEl("h2", { text: "Jelly Snippets - Settings" });

		new Setting(childEl)
			.setName("Snippets")
			.setDesc(
				"Specify your snippets here! Format: 'before<divider>after'. Surrounding your divider with a space is recommended for readability."
			)
			.addTextArea((textarea) =>
				textarea
					.setPlaceholder(
						`before${this.plugin.settings.snippetPartDivider}after`
					)
					.setValue(this.plugin.settings.snippetsFile)
					.onChange(async (value) => {
						this.plugin.settings.snippetsFile = value;
						await this.plugin.saveSettings();
						this.plugin.reloadSnippets(); // ? is this necessary to update the snippets?
					})
			);

		new Setting(childEl)
			.setName("Snippet line divider")
			.setDesc(
				"This string will divide each separate snippet definition. (Enter the two characters '\\n' to use newlines as your separator.)"
			)
			.addText((text) =>
				text
					.setPlaceholder("-==-")
					.setValue(this.plugin.settings.snippetDivider)
					.onChange(async (value) => {
						this.plugin.settings.snippetDivider = value;
						await this.plugin.saveSettings();
					})
			);

		new Setting(childEl)
			.setName("Snippet part divider")
			.setDesc(
				"This string will divide the lhs and rhs of a snippet definition. (I recommend putting spaces in the ends of this string.)"
			)
			.addText((text) =>
				text
					.setPlaceholder(" |+| ")
					.setValue(this.plugin.settings.snippetPartDivider)
					.onChange(async (value) => {
						this.plugin.settings.snippetPartDivider = value;
						await this.plugin.saveSettings();
					})
			);

		new Setting(childEl)
			.setName("Trigger on Space")
			.setDesc(
				"If enabled, the snippet function will trigger when space is pressed (but not while shift is held)."
			)
			.addDropdown((dropdown) =>
				dropdown
					.addOption(AutoTriggerOptions.Disabled, "Disabled")
					// .addOption(AutoTriggerOptions.EnabledNoWS, "Enabled, no whitespace")
					.addOption(
						AutoTriggerOptions.EnabledYesWS,
						"Enabled, also space"
					)
					.setValue(this.plugin.settings.triggerOnSpace)
					.onChange(async (value) => {
						this.plugin.settings.triggerOnSpace =
							value as AutoTriggerOptions;
						await this.plugin.saveSettings();
					})
			);

		new Setting(childEl)
			.setName("Trigger on Enter")
			.setDesc(
				"If enabled, the snippet function will trigger when enter is pressed (but not while shift is held)."
			)
			.addDropdown((dropdown) =>
				dropdown
					.addOption(AutoTriggerOptions.Disabled, "Disabled")
					.addOption(
						AutoTriggerOptions.EnabledNoWS,
						"Enabled, no newline"
					)
					.addOption(
						AutoTriggerOptions.EnabledYesWS,
						"Enabled, also newline"
					)
					.setValue(this.plugin.settings.triggerOnEnter)
					.onChange(async (value) => {
						this.plugin.settings.triggerOnEnter =
							value as AutoTriggerOptions;
						await this.plugin.saveSettings();
					})
			);

		new Setting(childEl)
			.setName("Trigger on Tab")
			.setDesc(
				"If enabled, the snippet function will trigger when tab is pressed (but not while shift is held)."
			)
			.addDropdown((dropdown) =>
				dropdown
					.addOption(AutoTriggerOptions.Disabled, "Disabled")
					.addOption(
						AutoTriggerOptions.EnabledNoWS,
						"Enabled, no indent"
					)
					.addOption(
						AutoTriggerOptions.EnabledYesWS,
						"Enabled, also indent on simple snippets (no newlines)"
					)
					.setValue(this.plugin.settings.triggerOnTab)
					.onChange(async (value) => {
						this.plugin.settings.triggerOnTab =
							value as AutoTriggerOptions;
						await this.plugin.saveSettings();
					})
			);
	}
}