const std = @import("std");
const util = @import("util");
const c = @cImport({
    @cInclude("sqlite3.h");
});

const Uuid = util.Uuid;
const DateTime = util.DateTime;

const UnexpectedError = error{Unexpected};

pub const OpenError = error{
    DbCorrupt,
    BadPathName,
    IsDir,
    InputOutput,
    NoSpaceLeft,
} || UnexpectedError;
pub const PrepareError = UnexpectedError;
pub const RowGetError = error{ InvalidData, StreamTooLong, OutOfMemory } || UnexpectedError;
pub const BindError = UnexpectedError;

fn getCharPos(text: []const u8, offset: c_int) struct { row: usize, col: usize } {
    var row: usize = 0;
    var col: usize = 0;
    var i: usize = 0;

    if (offset > text.len) return .{ .row = 0, .col = 0 };

    while (i != offset) : (i += 1) {
        if (text[i] == '\n') {
            row += 1;
            col = 0;
        } else {
            col += 1;
        }
    }

    return .{ .row = row, .col = col };
}

fn handleUnexpectedError(db: *c.sqlite3, code: c_int, sql_text: ?[]const u8) UnexpectedError {
    std.log.err("Unexpected error in SQLite engine: {s} ({})", .{ c.sqlite3_errstr(code), code });

    std.log.debug("Additional details:", .{});
    std.log.debug("{?s}", .{c.sqlite3_errmsg(db)});
    if (sql_text) |sql| {
        const byte_offset = c.sqlite3_error_offset(db);
        if (byte_offset >= 0) {
            const pos = getCharPos(sql, byte_offset);
            std.log.debug("Failed at char ({}:{}) of SQL:\n{s}", .{ pos.row, pos.col, sql });
        }
    }
    std.log.debug("{?s}", .{@errorReturnTrace()});

    return error.Unexpected;
}

pub const Sqlite = struct {
    db: *c.sqlite3,

    pub fn open(path: [:0]const u8) OpenError!Sqlite {
        const flags = c.SQLITE_OPEN_READWRITE | c.SQLITE_OPEN_CREATE | c.SQLITE_OPEN_EXRESCODE;

        var db: ?*c.sqlite3 = undefined;
        switch (c.sqlite3_open_v2(@ptrCast([*c]const u8, path), &db, flags, null)) {
            c.SQLITE_OK => {},
            c.SQLITE_NOTADB, c.SQLITE_CORRUPT => return error.DbCorrupt,
            c.SQLITE_IOERR_WRITE, c.SQLITE_IOERR_READ => return error.InputOutput,
            c.SQLITE_CANTOPEN_ISDIR => return error.IsDir,
            c.SQLITE_CANTOPEN_FULLPATH => return error.BadPathName,
            c.SQLITE_FULL => return error.NoSpaceLeft,

            else => |err| {
                std.log.err(
                    \\Unable to open SQLite DB "{s}"
                    \\Error: {s} ({})
                , .{ path, c.sqlite3_errstr(err), err });

                return error.Unexpected;
            },
        }

        return Sqlite{
            .db = db.?,
        };
    }

    pub fn close(self: Sqlite) void {
        switch (c.sqlite3_close(self.db)) {
            c.SQLITE_OK => {},

            c.SQLITE_BUSY => {
                std.log.err("SQLite DB could not be closed as it is busy.\n{s}", .{c.sqlite3_errmsg(self.db)});
            },

            else => |err| {
                std.log.err("Could not close SQLite DB", .{});
                handleUnexpectedError(self.db, err, null) catch {};
            },
        }
    }

    pub fn prepare(self: *Sqlite, sql: []const u8) PrepareError!PreparedStmt {
        var stmt: ?*c.sqlite3_stmt = undefined;
        const err = c.sqlite3_prepare_v2(self.db, sql.ptr, @intCast(c_int, sql.len), &stmt, null);
        if (err != c.SQLITE_OK) return handleUnexpectedError(self.db, err, sql);

        return PreparedStmt{ .stmt = stmt.?, .db = self.db };
    }
};

pub const Row = struct {
    stmt: *c.sqlite3_stmt,
    db: *c.sqlite3,

    pub fn isNull(self: Row, idx: u15) RowGetError!bool {
        return c.sqlite3_column_type(self.stmt, idx) == c.SQLITE_NULL;
    }

    pub fn getI64(self: Row, idx: u15) RowGetError!i64 {
        return @intCast(i64, c.sqlite3_column_int64(self.stmt, idx));
    }

    pub fn getText(self: Row, idx: u15, buf: []u8) RowGetError![]u8 {
        const ptr = c.sqlite3_column_text(self.stmt, idx);

        const size = @intCast(usize, c.sqlite3_column_bytes(self.stmt, idx));
        if (size > buf.len) return error.StreamTooLong;
        for (ptr[0..size]) |ch, i| buf[i] = ch;

        return buf[0..size];
    }

    pub fn getTextAlloc(self: Row, idx: u15, alloc: std.mem.Allocator) RowGetError![]u8 {
        const size = c.sqlite3_column_bytes(self.stmt, idx);
        var buf = try alloc.alloc(u8, @intCast(usize, size));
        errdefer alloc.free(buf);

        return self.getText(idx, buf);
    }

    pub fn getBlob(self: Row, idx: u15, buf: []u8) RowGetError![]u8 {
        const ptr = @ptrCast([*]const u8, c.sqlite3_column_blob(self.stmt, idx));

        const size = @intCast(usize, c.sqlite3_column_bytes(self.stmt, idx));
        if (size > buf.len) return error.StreamTooLong;
        for (ptr[0..size]) |ch, i| buf[i] = ch;

        return buf[0..size];
    }

    pub fn getBlobAlloc(self: Row, idx: u15, alloc: std.mem.Allocator) RowGetError![]u8 {
        const size = c.sqlite3_column_bytes(self.stmt, idx);
        var buf = try alloc.alloc(u8, @intCast(usize, size));
        errdefer alloc.free(buf);

        return self.getBlob(idx, buf);
    }

    pub fn getUuid(self: Row, idx: u15) RowGetError!Uuid {
        var buf: [Uuid.string_len + 1]u8 = undefined;
        _ = try self.getText(idx, &buf);
        return Uuid.parse(buf[0..Uuid.string_len]) catch return error.InvalidData;
    }

    pub fn getDateTime(self: Row, idx: u15) RowGetError!DateTime {
        return DateTime{ .seconds_since_epoch = try self.getI64(idx) };
    }
};

pub const PreparedStmt = struct {
    stmt: *c.sqlite3_stmt,
    db: *c.sqlite3,

    pub fn bindNull(self: PreparedStmt, idx: u15) BindError!void {
        return switch (c.sqlite3_bind_null(self.stmt, idx)) {
            c.SQLITE_OK => {},
            else => |err| handleUnexpectedError(self.db, err, null),
        };
    }

    pub fn bindUuid(self: PreparedStmt, idx: u15, id: Uuid) BindError!void {
        const str = id.toCharArray();
        return self.bindText(idx, &str);
    }

    pub fn bindText(self: PreparedStmt, idx: u15, str: []const u8) BindError!void {
        // Work around potential null pointer in empty string
        const eff_str = if (str.len == 0) (" ")[0..0] else str;
        return switch (c.sqlite3_bind_text(self.stmt, idx, eff_str.ptr, @intCast(c_int, eff_str.len), c.SQLITE_TRANSIENT)) {
            c.SQLITE_OK => {},
            else => |err| handleUnexpectedError(self.db, err, null),
        };
    }

    pub fn bindBlob(self: PreparedStmt, idx: u15, blob: []const u8) BindError!void {
        return switch (c.sqlite3_bind_blob64(self.stmt, idx, blob.ptr, blob.len, c.SQLITE_TRANSIENT)) {
            c.SQLITE_OK => {},
            else => |err| handleUnexpectedError(self.db, err, null),
        };
    }

    pub fn bindI64(self: PreparedStmt, idx: u15, val: i64) BindError!void {
        return switch (c.sqlite3_bind_int64(self.stmt, idx, val)) {
            c.SQLITE_OK => {},
            else => |err| handleUnexpectedError(self.db, err, null),
        };
    }

    pub fn bindDateTime(self: PreparedStmt, idx: u15, val: DateTime) BindError!void {
        return self.bindI64(idx, val.seconds_since_epoch);
    }

    pub const StepError = UnexpectedError;
    pub fn step(self: PreparedStmt) !?Row {
        return switch (c.sqlite3_step(self.stmt)) {
            c.SQLITE_ROW => Row{ .stmt = self.stmt, .db = self.db },
            c.SQLITE_DONE => null,

            else => |err| handleUnexpectedError(self.db, err, self.getGeneratingSql()),
        };
    }

    pub fn finalize(self: PreparedStmt) void {
        switch (c.sqlite3_finalize(self.stmt)) {
            c.SQLITE_OK => {},
            else => |err| {
                handleUnexpectedError(self.db, err, self.getGeneratingSql()) catch {};
            },
        }
    }

    pub fn reset(self: PreparedStmt) void {
        switch (c.sqlite3_reset(self.stmt)) {
            c.SQLITE_OK => {},
            else => |err| {
                handleUnexpectedError(self.db, err, self.getGeneratingSql()) catch {};
            },
        }
    }

    fn getGeneratingSql(self: PreparedStmt) ?[]const u8 {
        const ptr = c.sqlite3_sql(self.stmt) orelse return null;
        return ptr[0..std.mem.len(ptr)];
    }
};